# MillerModSaws and the PS-7910



## MillerModSaws (Feb 16, 2015)

Ok boys here we go. I promised a build thread on these baby's so here we go. I would ask that you bear with me as I am slow when building a saw for the first time. Wait I'm slow all the time. Lol. Anyway this is my first go at these so please feel free to make suggestions or tell me if I'm headed in the wrong direction. Here's the victims! A pair of brand new 7910s.


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## Moparmyway (Feb 16, 2015)

Subscribed !!
looking forward to this project !


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## MillerModSaws (Feb 16, 2015)

Here's the intial numbers. Ex 106, trans are on a slant from 130-132, in 76. The squish is .025 with a gasket .015 without and comp is 165.


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## MillerModSaws (Feb 16, 2015)

Ok I started by doing a muffler mod. Know while I've never built a 7900 I see it has higher blow down than the 7910. And I'm guessing it has something to do with this SLR chamber thingy. But i heated up and opened the muffler up. I cut out the SLR unit but tack welded the flange from it back in from spacing and support. Then the area you see that I open up for the exit in a factory indentation. If you open it up you'll wind up right about 80%.


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## MillerModSaws (Feb 16, 2015)

A couple pics of tear down. You can see the tiny cranckcase volume everyone always talks about on these.


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## MillerModSaws (Feb 16, 2015)

Ok so I started by cutting .032" off the base and .038" off the squish band. I will be running this one without a gasket. With this amount off I'm getting really close to free porting at the bottom of the exhaust.


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## MillerModSaws (Feb 16, 2015)

My plans are for the first saw to gasket match the lower trans, square up and widen the intake just a bit. And set the exhaust at 102 with 27 degree blow down. I take will be at whatever the base cut left me with.


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## chris zautner (Feb 16, 2015)




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## MillerModSaws (Feb 16, 2015)

I started out by pushing the ring up in the cylinder and marking it at 102 deg and the marked my intial width. I remarked the width a couple times but I ended up about .078 from the skirt edges which give me roughly 60% exhaust to bore size.


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## MillerModSaws (Feb 16, 2015)

On the exhaust side there is a huge amount of blending to do. I was careful not to take any from the floor right at the piston. I may go back in and take the top and bottom slots all the way out from where the muffler slid in but this is a starting point.


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## MillerModSaws (Feb 16, 2015)

I have the lower and upper trans marked. I'm not going to widen the uppers as of yet. Just raise them o a flat 129°. I don't want to add to much width on them because of the cranckcase volume. That's sounds right in my head anyway. Lol. And this is as far as I have gotten.


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## Hedgerow (Feb 16, 2015)

Did these have the windowed piston?

Edit.. Never mind... I see it now..


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## MillerModSaws (Feb 16, 2015)

Hedgerow said:


> Did these have the windowed piston?
> 
> Edit.. Never mind... I see it now..


Here's another pic just for giggles than.


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## Hedgerow (Feb 16, 2015)

Very nice..


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## redoakman (Feb 16, 2015)

im in on this one


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## MillerModSaws (Feb 16, 2015)

Had just a little more time this evening so I went ahead and roughed in one side of the trans.


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## Deets066 (Feb 16, 2015)

Nice work, takes quite a bit of time huh.


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## MillerModSaws (Feb 16, 2015)

Deets066 said:


> Nice work, takes quite a bit of time huh.


Yes it does. Lol


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## Deets066 (Feb 16, 2015)

What are you using for polishing exhaust ports?


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## MillerModSaws (Feb 16, 2015)

Deets066 said:


> What are you using for polishing exhaust ports?


When I do my final polish I use silicone rubber polishing burrs and oil.


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## KG441c (Feb 16, 2015)

With the tight crankcase volume would raising the upper transfers higher than 129 be beneficial or not?


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## MillerModSaws (Feb 16, 2015)

KG441c said:


> With the tight crankcase volume would raising the upper transfers higher than 129 be beneficial or not?


Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.


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## Hedgerow (Feb 16, 2015)

MillerModSaws said:


> Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.


Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!


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## MillerModSaws (Feb 16, 2015)

Hedgerow said:


> Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..
> 
> Those folks at Dolmar sure didn't leave us any low hanging fruit!!


I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.


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## Hedgerow (Feb 16, 2015)

MillerModSaws said:


> I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.


Andy is as crazy as a shithouse rat...
Gotta watch that guy...


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## Hedgerow (Feb 16, 2015)




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## MillerModSaws (Feb 16, 2015)

Hedgerow said:


> Andy is as crazy as a shithouse rat...
> Gotta watch that guy...


I'm sure he'll be along to defend that statement. Lmao. But by the end of this thread hopefully we have an awesome recipe going for this saw.


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## drf255 (Feb 17, 2015)

Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?

My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?


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## Hedgerow (Feb 17, 2015)

drf255 said:


> Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?
> 
> My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?


Some say Stihl transfers are a bit lazy and require more time open.. 
A head start you could say.. 
But that varies from model to model..


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## MillerModSaws (Feb 17, 2015)

Hedgerow said:


> Some say Stihl transfers are a bit lazy and require more time open..
> A head start you could say..
> But that varies from model to model..


An example of model to model. I set the ms441 at 25° blowdown.


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## blsnelling (Feb 17, 2015)

MillerModSaws said:


> I set the ms441 at 25° blowdown.


That's a lot.


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## KG441c (Feb 17, 2015)

blsnelling said:


> That's a lot.


Would u explain Brad? Thanks


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## ELECT6845 (Feb 17, 2015)

MillerModSaws said:


> An example of model to model. I set the ms441 at 25° blowdown.


I have been leaving more blowdown in the new model Stihls along with more intake. They seem to like it and make alittle more torque. Guess it all comes down to what a guy prefers.


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## MillerModSaws (Feb 17, 2015)

blsnelling said:


> That's a lot.


What do u use. I take .050 off squish band. 100/125/78 iirc. But that seems to be the best combo I've found so far. I did try 23 blowdown and maybe it was the combo I tried but it like 25 blowdown better.


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## blsnelling (Feb 17, 2015)

I don't want to quote any numbers until I'm home to check my records.


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## mdavlee (Feb 17, 2015)

Hedgerow said:


> Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..
> 
> Those folks at Dolmar sure didn't leave us any low hanging fruit!!


Your red one has 30° of blowdown. if I remember right it has 45° of crankcase compression.


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## blsnelling (Feb 17, 2015)

In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?


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## old-cat (Feb 17, 2015)

Hedgerow said:


> Blowdown and degrees of crank case compression are important on these saws..


Another saw with small crankcase volume is the 357xp and the oem timing is ex. 106, transfer 118, intake 73
Thats 12 degrees blowdown!????????


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## komatsuvarna (Feb 17, 2015)

blsnelling said:


> In my limited experience with these, they need LOTS of blowdown. And, *simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.*
> 
> What's the stock exhaust port timing on a 7900?



I agree, it doesn't.

The transfers will still be too high..


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## MillerModSaws (Feb 17, 2015)

blsnelling said:


> In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.
> 
> What's the stock exhaust port timing on a 7900?


I'll agree to however. In building these I want to try a 100 degree exhaust height. See how that works. So I would be at 100/127 if I tried that. Stock exhaust height from what I've read is 105 on the 7900 with 27 blowdown.


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## Hedgerow (Feb 17, 2015)

mdavlee said:


> Your red one has 30° of blowdown. if I remember right it has 45° of crankcase compression.


And runs like a champ.. But it's also built on a whole different premiss..
And only 170 lbs of comp..


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## Hedgerow (Feb 17, 2015)

old-cat said:


> Another saw with small crankcase volume is the 357xp and the oem timing is ex. 106, transfer 118, intake 73
> Thats 12 degrees blowdown!????????


They put stuffers in the 357, but I'm not sure it's volume would be considered small. It may have more than the 7900 does even with the stuffers.. 
Maybe someone has measured??


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## KG441c (Feb 17, 2015)

Would someone please explain blowdown and effects of being too high or low?


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## mdavlee (Feb 17, 2015)

The 576 has short blowdown also. 13-14° is what I remember. Too long of blowdown in some saws will hold them back at higher rpms.


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## Hedgerow (Feb 17, 2015)

KG441c said:


> Would someone please explain blowdown and effects of being too high or low?


Blowdown = degrees of rotation between exhaust opening and upper transfers opening. There really is no "too high" or "too low" as it would apply to all designs.. Cause they all different..
It's like making cookies...
7900's are tough cookies to improve on...
Not impossible, just tough...
I'm glad millermod is willing to explore the 7910's..
Cause judging by the one we been running, they've proven themselves to be extremely durable and a way better tool for commercial users than the 372XT's. 
Just my opinion though..


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## KG441c (Feb 17, 2015)

And where would u start from saw to saw in determining what blowdown to shoot for? Thanks for explanation


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## old-cat (Feb 17, 2015)

KG441c said:


> Would someone please explain blowdown and effects of being too high or low?


If you go too high with the transfer, it KILLS the low speed power. Ask me how I know


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## Mastermind (Feb 17, 2015)

102 is as high as I like the exhaust on these......unless it's a 20" bar saw. 

Watch widening the uppers.......you'll catch a ring.


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## Hedgerow (Feb 17, 2015)

KG441c said:


> And where would u start from saw to saw in determining what blowdown to shoot for? Thanks for explanation


You do your best to figure out what premiss the original designers built the saw under and work with it. "Improve on it"


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## Mastermind (Feb 17, 2015)

Hedgerow said:


> You do your best to figure out what premiss the original designers built the saw under and work with it. "Improve on it"



Very well said.......

Anytime we start thinking "they" had no idea what they were thinking.......we start going backward. 

The 7900/10s I build hold more RPM in the cut than any other 70 - 80cc saw I do. They are just awesome.


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## KG441c (Feb 17, 2015)

old-cat said:


> If you go too high with the transfer, it KILLS the low speed power. Ask me how I know


Hack that furball up!! Lets hear it!!! Lol!!


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## jar944 (Feb 17, 2015)

I'm curious to see what you find, as I'm working on a AM 7900 jug now.


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## Mastermind (Feb 17, 2015)

About 27 degrees of blowdown.......102 exhaust......no more than 80 on the intake........


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## drf255 (Feb 17, 2015)

So the lower the intake floor, the less case compression, and the more blowdown/higher transfers you need?

If intake floor higher, more case compression, lower blowdown?


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## Mastermind (Feb 17, 2015)

Al, there are very few hard and fast rules to porting these engines. What Matt posted about transfer passage size sorta nails it though. Dual open style transfers seem to like higher transfer opening points........tighter fast flowing transfer passages work at lower points. The 7900/10 is an odd duck in all this though. If you take the transfers too high on it.........you've created a turd.


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## wigglesworth (Feb 17, 2015)

Mastermind said:


> Al, there are very few hard and fast rules to porting these engines. What Matt posted about transfer passage size sorta nails it though. Dual open style transfers seem to like higher transfer opening points........tighter fast flowing transfer passages work at lower points. The 7900/10 is an odd duck in all this though. If you take the transfers too high on it.........you've created a turd.



I created a turd earlier today....


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## Mastermind (Feb 17, 2015)

You are a turd.


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## wigglesworth (Feb 17, 2015)

Mastermind said:


> You are a turd.


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## MillerModSaws (Feb 17, 2015)

Mastermind said:


> About 27 degrees of blowdown.......102 exhaust......no more than 80 on the intake........


Thats exactly where this one is headed. Lmao. But if above 102 kills them I won't explore that option. Thank you.


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## KG441c (Feb 17, 2015)

Mastermind said:


> Al, there are very few hard and fast rules to porting these engines. What Matt posted about transfer passage size sorta nails it though. Dual open style transfers seem to like higher transfer opening points........tighter fast flowing transfer passages work at lower points. The 7900/10 is an odd duck in all this though. If you take the transfers too high on it.........you've created a turd.


How does this 7910 compare to a 461 in comparison in case volume and blowdown?


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## blsnelling (Feb 17, 2015)

I find the 461 to run best with short blowdown and long intake.


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## MillerModSaws (Feb 17, 2015)

Remember boys when I get this one built and see gains or losses we have 1 more so number suggestions are more than welcome to compare the 2. I am basically trying to work up an really good work saw recipe for this saw. Hopefully this will benifit all.


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## blsnelling (Feb 17, 2015)

I'd keep the exhaust down on the next one. Raising the exhaust doesn't always make more RPMs. Look at the 346. I find that they run best with the exhaust at 105°-107°.


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## KG441c (Feb 17, 2015)

MillerModSaws said:


> Remember boys when I get this one built and see gains or losses we have 1 more so number suggestions are more than welcome to compare the 2. I am basically trying to work up an really good work saw recipe for this saw. Hopefully this will benifit all.


This should be a good thread


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## KG441c (Feb 17, 2015)

blsnelling said:


> I find the 461 to run best with short blowdown and long intake.


What #s Brad?


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## Hedgerow (Feb 17, 2015)

blsnelling said:


> I'd keep the exhaust down on the next one. Raising the exhaust doesn't always make more RPMs. Look at the 346. I find that they run best with the exhaust at 105°-107°.


Baby saw...


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## Hedgerow (Feb 17, 2015)

MillerModSaws said:


> Remember boys when I get this one built and see gains or losses we have 1 more so number suggestions are more than welcome to compare the 2. I am basically trying to work up an really good work saw recipe for this saw. Hopefully this will benifit all.


If you took less out of the squish band, you could try one at 99 ex or so and go back if need be and correct.


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## Mastermind (Feb 17, 2015)

MillerModSaws said:


> Thats exactly where this one is headed. Lmao. But if above 102 kills them I won't explore that option. Thank you.



I'm not saying it will kill it........the exhaust height isn't the most critical element on this saw. Transfer height is. That said.....raising the exhaust isn't too beneficial either. Working RPM seems to come from engine design rather than porting. 

Now when you start building saws that you wanna see really spin.......less compression, both primary and secondary, helps free up rpm.


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## KG441c (Feb 17, 2015)

So Randy this 7910s dual ports volume is already close to max without raising transfers much? Where is the biggest gain on this saw? Compression?


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## Mastermind (Feb 17, 2015)

I'm not sure that I could nail down any one thing that nets the biggest gain........

Let's see what the OP comes up with here........I've derailed enough. lol


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## KG441c (Feb 17, 2015)

I hear u! Ive talked with Gary in pm on this one alil and interested in his build. Im just tryin to learn all I can while I got all u gurus in one place!!


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## MillerModSaws (Feb 17, 2015)

Mastermind said:


> I'm not sure that I could nail down any one thing that nets the biggest gain........
> 
> Let's see what the OP comes up with here........I've derailed enough. lol


Derail away. This build thread will be slow as I don't have a lot of time in the evenings. The entertainment level must be kept up. Lol. I was just to anxious to see what u could do with one of these bad boys.


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## MillerModSaws (Feb 17, 2015)

I marked out what I'm gonna do with the base but the side of the lower trans is still in thought process. Really leaning towards squaring the rear up like the front. Raising it the amount I took off the base and come out from the base square. So let's here some comments here.


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## Mastermind (Feb 17, 2015)

I wouldn't touch it.


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## MillerModSaws (Feb 17, 2015)

And when I i saw come out from the base. I'm mean take the red lines straight into the bore.


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## jar944 (Feb 17, 2015)

MillerModSaws said:


> View attachment 404434
> And when I i saw come out from the base. I'm mean take the red lines straight into the bore.



You want the entrance of the transfer ducts side walls to be the same angle as the exit. Twisted ducts reduce flow.


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## MillerModSaws (Feb 17, 2015)

Mastermind said:


> I wouldn't touch it.


Not


Mastermind said:


> I wouldn't touch it.


Not even case matching the base or just the sides?


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## Flattop Burns (Feb 17, 2015)

Sachs Dolmar was always a good thing. Are they still German or is it chinese because of when Makita bought them out? By the way the Makitas look just like those things same saw in blue in my opinion.


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## mdavlee (Feb 17, 2015)

MillerModSaws said:


> Not
> 
> Not even case matching the base or just the sides?


If you're going after long bar torque leave it.


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## Mastermind (Feb 17, 2015)

Think about this.........every grain of material you remove will lower case compression.


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## shorthunter (Feb 17, 2015)

MillerModSaws said:


> Thats exactly where this one is headed. Lmao. But if above 102 kills them I won't explore that option. Thank you.



I ported my 7900 and picked up roughly 12% on timed cuts in a 12" oak cant log. I ended up at 101 on the exhaust, 130 on the transfers and 80.5 on the intake but I also used a 460 piston with an aluminum base gasket/ spacer. It runs a 28" bar with an 8 pin sprocket and full comp chain really well. I am planning to raise the exhaust a little more and to replace the coil with an unlimited unit. Then I will do a build thread with a comparison to a stock 7900 with the slab sided piston


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## MillerModSaws (Feb 17, 2015)

Mastermind said:


> Think about this.........every grain of material you remove will lower case compression.


Ok. I see. I was thinking flow.


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## MillerModSaws (Feb 17, 2015)

shorthunter said:


> I ported my 7900 and picked up roughly 12% on timed cuts in a 12" oak cant log. I ended up at 101 on the exhaust, 130 on the transfers and 80.5 on the intake but I also used a 460 piston with an aluminum base gasket/ spacer. It runs a 28" bar with an 8 pin sprocket and full comp chain really well. I am planning to raise the exhaust a little more and to replace the coil with an unlimited unit. Then I will do a build thread with a comparison to a stock 7900 with the slab sided piston


What are you using for an unlimited coil?


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## Mastermind (Feb 17, 2015)

MillerModSaws said:


> Ok. I see. I was thinking flow.



One more tidbit......

Remember that transfer flow is forced........the piston displaces the mixture upward into the combustion area. Looking at scavenging into the jug might be more helpful than looking at the entrance.


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## cuttinties (Feb 17, 2015)

shorthunter said:


> I ported my 7900 and picked up roughly 12% on timed cuts in a 12" oak cant log. I ended up at 101 on the exhaust, 130 on the transfers and 80.5 on the intake but I also used a 460 piston with an aluminum base gasket/ spacer. It runs a 28" bar with an 8 pin sprocket and full comp chain really well. I am planning to raise the exhaust a little more and to replace the coil with an unlimited unit. Then I will do a build thread with a comparison to a stock 7900 with the slab sided piston


272xp coil.


MillerModSaws said:


> Ok. I see. I was thinking flow.


Doesn't matter what you flow through if you don't use it efficiently. Don't put more in than you can transfer. Boils down to if you over fill the case it will spit back. That's wasted charge and not only that, it decreases transfer velocity. Same goes for the tunnels and upper transfers. Size does matter but more isn't always better. One thing I continue to see on Dolmar saws is the less is more approach yields the best gains. Mileage varies but don't feel like you need to change already good thing so much.


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## shorthunter (Feb 17, 2015)

MillerModSaws said:


> What are you using for an unlimited coil?



Husqvarna 50/51/55/262/272 coil


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## Hedgerow (Feb 17, 2015)

MillerModSaws said:


> What are you using for an unlimited coil?


You must re-index the flywheel when making this change over..


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## SCHallenger (Feb 17, 2015)




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## mdavlee (Feb 17, 2015)

Hedgerow said:


> You must re-index the flywheel when making this change over..


Ever get your 2 done?


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## Hedgerow (Feb 17, 2015)

mdavlee said:


> Ever get your 2 done?


Nope... Still procrastinating... And filing chains...
I think someone could port a saw faster than I can file a good chain..


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## awol (Feb 17, 2015)

One of 'em may be done, just have to finish the rest of the saw to find out how it works! 
On the subject of case volume in relation to trans duration, I think there is a lot of performance left untapped in these saws, simply because the right combination of duration, location, and size of the transfers has not been discovered.


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## jar944 (Feb 17, 2015)

awol said:


> I think there is a lot of performance left untapped in these saws, simply because the right combination of duration, location, and size of the transfers has not been discovered.



Cheaper than cutting and testing hundreds of possible combinations, and proven accurate by some top 2t tuners. Provided the inputs are correct.
http://www.vannik.co.za/EngMod2TDetails.htm


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## fordf150 (Feb 17, 2015)




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## redfin (Feb 17, 2015)

mdavlee said:


> If you're going after long bar torque leave it.





Mastermind said:


> Think about this.........every grain of material you remove will lower case compression.



Thinking about this made me think of how Scott matches this piston to the lower opening of the transfers in I think it was a 385? Would that net a lower case compression?


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## mdavlee (Feb 17, 2015)

redfin said:


> Thinking about this made me think of how Scott matches this piston to the lower opening of the transfers in I think it was a 385? Would that net a lower case compression?


Yes. A 385 has a lot more case capacity over a 7900 also.


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## Andyshine77 (Feb 17, 2015)

You can go as high as 100° on the exhaust, especially with the added compression, I personally would stay around 101°-102° With the small intake and carb, extra intake duration works just fine on the 7900. Blowdown yes you want a lot of that 25° or more. You did the right thing with the intake side transfer, I've seen them ever larger. 
You should have a pretty good running 7900 on your hands.


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## MillerModSaws (Feb 17, 2015)

A little progress tonight. I hot the upper trans done. I went back in and squared them up a little compared to what I had roughed in then finished them with a diamond burr.


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## Andyshine77 (Feb 17, 2015)

Should work. What's final squish at?


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## MillerModSaws (Feb 17, 2015)

Andyshine77 said:


> Should work. What's final squish at?


.021"


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## Mastermind (Feb 17, 2015)

Andyshine77 said:


> You can go as high as 100° on the exhaust, especially with the added compression, I personally would stay around 101°-102° With the small intake and carb, extra intake duration works just fine on the 7900. Blowdown yes you want a lot of that 25° or more. You did the right thing with the intake side transfer, I've seen them ever larger.
> You should have a pretty good running 7900 on your hands.



Keep in mind.......this is a 7910. The ring pin will end up in the transfer port if they are widened too much.


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## drf255 (Feb 17, 2015)

MillerModSaws said:


> View attachment 404433
> I marked out what I'm gonna do with the base but the side of the lower trans is still in thought process. Really leaning towards squaring the rear up like the front. Raising it the amount I took off the base and come out from the base square. So let's here some comments here.


I got a comment. 

Really nice farking porting going on there. Clean stuff.....


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## Andyshine77 (Feb 17, 2015)

Mastermind said:


> Keep in mind.......this is a 7910. The ring pin will end up in the transfer port if they are widened too much.



Where is the pin end? it's not centered with the intake port?


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## Mastermind (Feb 17, 2015)

Andyshine77 said:


> Where is the pin end? it's not centered with the intake port?



Nope........off to the side.


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## Andyshine77 (Feb 17, 2015)

MillerModSaws said:


> .021"



I don't suggest it, but I've seen .010" on a few 7900 work saws. I like .017-.020 myself.


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## MillerModSaws (Feb 17, 2015)

On the intake I did very little. I squared squared the corners up just a bit and widened just a little and I mean a little. I didn't do much more than knock the nikasil overlap off. And then smoothed the intake tunnel up getting rid of all the ridges. It's sitting at exactly 80° right now.


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## Andyshine77 (Feb 17, 2015)

Mastermind said:


> Nope........off to the side.



That sucks.


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## CR888 (Feb 17, 2015)

l think these saws run well stock....but that aint exactly any help here. Well engineered jugs.


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## MillerModSaws (Feb 17, 2015)

Andyshine77 said:


> Where is the pin end? it's not centered with the intake port?


Here it is. Lol.


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## Andyshine77 (Feb 17, 2015)

MillerModSaws said:


> View attachment 404561
> 
> Here it is. Lol.



I liked that post, but I don't really like it.


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## Mastermind (Feb 17, 2015)

IMHO widening the uppers is a mistake. They will scavenge better if they aren't overly wide.


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## MillerModSaws (Feb 17, 2015)

Mastermind said:


> IMHO widening the uppers is a mistake. They will scavenge better if they aren't overly wide.


These are not widen. If they are it's just from cleanup.


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## Mastermind (Feb 17, 2015)

MillerModSaws said:


> These are not widen. If they are it's just from cleanup.



I could see that. 

I normally just take them out to edge of the factory bevels. 

Now on a 562XP.......I wrap em on around. The transfer flow comes in at a different angle on those though.


----------



## Hedgerow (Feb 17, 2015)

MillerModSaws said:


> View attachment 404561
> 
> Here it is. Lol.


It just wouldn't be a Dolmar project if them bastards didn't make it difficult...
Looks like good work so far...


----------



## LegDeLimber (Feb 18, 2015)

Do you still have that resonant chamber from inside of the muffler? 
If so, could you measure the volume of it?
Would prefer in CCs if you have something like an oil ratio cup.
Looks like you could hold it like I rotated your pic and depending on how wide,
I guess you would put your thumb or a piece of cardboard or a port blocking plate etc...
at the blue arrow and fill with water.

then one more request, please sir.
Could you post photos of it from the directions of the 3 red arrows.
Maybe a scale/ruler laying alongside would be just awesome.


----------



## Four Paws (Feb 18, 2015)

What good is more power to pull a long bar when you can't oil it? We should be discussing how to port the stingy Dolmar oiler.


----------



## Andyshine77 (Feb 18, 2015)

Mastermind said:


> IMHO widening the uppers is a mistake. They will scavenge better if they aren't overly wide.



It's more about direction of the charge than area IMHO.


----------



## MillerModSaws (Feb 18, 2015)

LegDeLimber said:


> Do you still have that resonant chamber from inside of the muffler?
> If so, could you measure the volume of it?
> Would prefer in CCs if you have something like an oil ratio cup.
> Looks like you could hold it like I rotated your pic and depending on how wide,
> ...


I already threw it away. However I will try and remember to do this when I do the second saw for you.


----------



## redfin (Feb 18, 2015)

Four Paws said:


> What good is more power to pull a long bar when you can't oil it? We should be discussing how to port the stingy Dolmar oiler.



Have you modded one Josh?


----------



## jar944 (Feb 18, 2015)

Four Paws said:


> What good is more power to pull a long bar when you can't oil it? We should be discussing how to port the stingy Dolmar oiler.



No porting involved but doubling the oil output has been figured out
http://www.arboristsite.com/community/threads/dolmar-makita-oil-pump-upgrade-modification.264696/


----------



## jar944 (Feb 18, 2015)

Andyshine77 said:


> It's more about direction of the charge than area IMHO.



Which is why IMHO kickers on the intake side of the B ports will help scavenging.


----------



## Four Paws (Feb 18, 2015)

redfin said:


> Have you modded one Josh?



No, I have not.



jar944 said:


> No porting involved but doubling the oil output has been figured out
> http://www.arboristsite.com/community/threads/dolmar-makita-oil-pump-upgrade-modification.264696/



Yes...fine work and excellent results. Glad you dropped in to share!


----------



## MillerModSaws (Feb 18, 2015)

Ok I got the exhaust gasket and flange port match. Didn't quite like how it turned out but I'm gonna give this a try.


----------



## MillerModSaws (Feb 18, 2015)

This is how much I'm going to haft to open up the muffler to match.


----------



## MillerModSaws (Feb 18, 2015)

The bases of the cylinders are pretty thin. So when I started this i choose to go without out a base gasket. So I dropped the jug .032 plus the thickness of the base gasket.


----------



## redfin (Feb 18, 2015)

What are your concerns regarding how it matched?


----------



## MillerModSaws (Feb 18, 2015)

And here's a pic I will prob catch crap over. I am the first to admit I have a lot to learn but here I know the air and gas mix is in a gas form not a liquid but I like to run them under the faucet to try to understand how the trans are flowing. This one in particular the exhaust side trans I may pull the the edge closet to the exhaust a little more straight out on the next build. But like I said this is more me learning how each cylinder flows. And the directions my port work is aiming. On the port you see flowing. Both sides were head towards the intake when I started and you can see how I pulled the middle of the port around just a bit towards the center of the piston.


----------



## MillerModSaws (Feb 18, 2015)

redfin said:


> What are your concerns regarding how it matched?


Not a lot of concern. I just don't think the slots from the original muffler look good. I'm kind of anal like that. Lol. Everyone likes pretty.


----------



## wigglesworth (Feb 18, 2015)

MillerModSaws said:


> View attachment 404808
> And here's a pic I will prob catch crap over. I am the first to admit I have a lot to learn but here I know the air and gas mix is in a gas form not a liquid but I like to run them under the faucet to try to understand how the trans are flowing. This one in particular the exhaust side trans I may pull the the edge closet to the exhaust a little more straight out on the next build. But like I said this is more me learning how each cylinder flows. And the directions my port work is aiming. On the port you see flowing. Both sides were head towards the intake when I started and you can see how I pulled the middle of the port around just a bit towards the center of the piston.



That's how I do it. 

Good looking build sir!


----------



## MillerModSaws (Feb 18, 2015)

wigglesworth said:


> That's how I do it.
> 
> Good looking build sir!


Sir. What the heck is that. Don't u know me better than that by now. Lmao.


----------



## redoakman (Feb 18, 2015)

MillerModSaws said:


> Sir. What the heck is that. Don't u know me better than that by now. Lmao.


hahah f uck i still call you sir hahah


----------



## MillerModSaws (Feb 18, 2015)

redoakman said:


> hahah f uck i still call you sir hahah


Well dam. Both of ya should know better. I havnt earned that title yet. Lmao. There are many others that I probably have though.


----------



## Mastermind (Feb 18, 2015)

I like turtles.


----------



## redoakman (Feb 18, 2015)

Mastermind said:


> I like turtles.


i think baby turtles are cuties


----------



## Mastermind (Feb 18, 2015)

wigglesworth said:


> That's how I do it.
> 
> Good looking build sir!



Yeah.....but what do you know? You ain't even got no stickers.


----------



## Mastermind (Feb 18, 2015)

redoakman said:


> i think baby turtles are cuties



Repped.


----------



## Deleted member 83629 (Feb 18, 2015)

stickers are a fad just like ported saws


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## MillerModSaws (Feb 18, 2015)

Mastermind said:


> I like turtles.


Turtles Wtf I swore the bush ape was on top of you list. And how the piss do I use these smiles. My phone always puts them at the very beginning. Cause I so would a put a ROFL there.


----------



## Mastermind (Feb 18, 2015)

Me and Ol' Brush Ape are good these days. Hell, I sorta like the guy.


----------



## jar944 (Feb 18, 2015)

MillerModSaws said:


> Both sides were head towards the intake when I started and you can see how I pulled the middle of the port around just a bit towards the center of the piston.



Its going to loose some of the charge out the exhaust port with the front of the A port now angled that way.


----------



## MillerModSaws (Feb 18, 2015)

jar944 said:


> Its going to loose some of the charge out the exhaust port with the front of the A port now angled that way.


I think I described it wrong. If u look at the flow now it more like the pic you have posted. Before it was angling towards the rear when flowing I removed just a little going back into the trans with the polishing bit and it pulled the flow around. I didn't widen the ports. Hope this makes sense.


----------



## Adirondackstihl (Feb 19, 2015)

I just ported in my pants


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## MillerModSaws (Feb 19, 2015)

All assemble with initial tune. I made a double d wrench to fit this carb I think it's gonna work pretty slick. I think it will stay right were it's at so I can tune in the cut. But i also slotted the end of the needle so who ever buys this won't haft to have the wrench.


----------



## MillerModSaws (Feb 19, 2015)

So here it is. With the initial tune. I will pull the b&c of my 375xp to get this saw tuned and keep the new b&c for the comparisson. I need a camera man. I need to order up an adapter so I can put my stihl 28" bar on it too.


----------



## drf255 (Feb 19, 2015)

MillerModSaws said:


> View attachment 404808
> And here's a pic I will prob catch crap over. I am the first to admit I have a lot to learn but here I know the air and gas mix is in a gas form not a liquid but I like to run them under the faucet to try to understand how the trans are flowing. This one in particular the exhaust side trans I may pull the the edge closet to the exhaust a little more straight out on the next build. But like I said this is more me learning how each cylinder flows. And the directions my port work is aiming. On the port you see flowing. Both sides were head towards the intake when I started and you can see how I pulled the middle of the port around just a bit towards the center of the piston.


Ive been doing it too. What the goal of flow here, forcing the charge back towards the intake, laterally across port to collide with each other, or towards the exhaust port?

Does anyone do any assymetric work on the ports so the the flow is in different directions to compliment each other?


----------



## Hedgerow (Feb 19, 2015)

drf255 said:


> Ive been doing it too. What the goal of flow here, forcing the charge back towards the intake, laterally across port to collide with each other, or towards the exhaust port?
> 
> Does anyone do any assymetric work on the ports so the the flow is in different directions to compliment each other?


Yes...
Husqvarna does it on the 372 from the factory..


----------



## MillerModSaws (Feb 19, 2015)

Hedgerow said:


> Yes...
> Husqvarna does it on the 372 from the factory..


O don't leave out the stihl heads buddy. The 361 is a good example of one port flat the other angled towards the combustion chamber.


----------



## jar944 (Feb 19, 2015)

drf255 said:


> Ive been doing it too. What the goal of flow here, forcing the charge back towards the intake, laterally across port to collide with each other, or towards the exhaust port?
> 
> Does anyone do any assymetric work on the ports so the the flow is in different directions to compliment each other?



Don't forget that in addition to efficient chamber filling, the transfers through directing the intake charge are used to "sweep out" the combustion gasses. Remove certain symmetric flow and you will have problems.


----------



## MillerModSaws (Feb 19, 2015)

I've let the saw run now for about five minutes while tuning Yada yada. Let cool and I'm pulling about 180 comp. I was hoping for just a bit more.


----------



## Andyshine77 (Feb 19, 2015)

Are you using a good gauge? the cheap ones seem to blow out the O-ring at higher psi. I ask because my bone stock 7900 makes just over 180psi, I'm thinking you have a gauge issue.


----------



## MillerModSaws (Feb 19, 2015)

Andyshine77 said:


> Are you using a good gauge? the cheap ones seem to blow out the O-ring at higher psi. I ask because my bone stock 7900 makes just over 180psi, I'm thinking you have a gauge issue.


Yes I have a lisle and it's been good so far. I think. Lol.


----------



## Andyshine77 (Feb 19, 2015)

MillerModSaws said:


> Yes I have a lisle and it's been good so far. I think. Lol.



Okay, in that case it may very well be reading a little low. Snap-On is the only gauge that I fully trust. So how does she feel so far?


----------



## MillerModSaws (Feb 19, 2015)

Andyshine77 said:


> Okay, in that case it may very well be reading a little low. Snap-On is the only gauge that I fully trust. So how does she feel so far?


I will let you know when I get to run here! I'm anxious to see if there's any good gains!


----------



## Poleman (Feb 20, 2015)

Whats your elevation?? I'm at 4000ft and have to compensate. A 150 lb reading would be around 170 sea leavel. Use to drive me nuts trying to figure out how everyone else was getting such good and higher readings!!


----------



## wigglesworth (Feb 20, 2015)

Andyshine77 said:


> Okay, in that case it may very well be reading a little low. Snap-On is the only gauge that I fully trust. So how does she feel so far?



All I can afford is Snap-off's™...


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## MillerModSaws (Feb 20, 2015)

Well v the lisle didn't hold up. Does this look better boys!


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## MillerModSaws (Feb 20, 2015)

I'm ready but no camera man. I really gotta buy a video camera and tripod. Lol


----------



## redoakman (Feb 20, 2015)

MillerModSaws said:


> View attachment 405537
> I'm ready but no camera man. I really gotta buy a video camera and tripod. Lol


lots of duct tape and something to tape it on lol


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## MillerModSaws (Feb 20, 2015)

redoakman said:


> lots of duct tape and something to tape it on lol


That would work if I didn't use my phone right now as a video camera


----------



## mdavlee (Feb 20, 2015)

I use my phone propped on something any more.


----------



## cuttinties (Feb 20, 2015)

Cut a stick of wood off like you'd put in the stove. Then cut a slot to sit your phone.


----------



## komatsuvarna (Feb 20, 2015)

mdavlee said:


> I use my phone propped on something any more.


Motorola props up perfect on a little orange screwdriver stuck in a stick of firewood! lol


----------



## mdavlee (Feb 20, 2015)

Yeah I stuck a sliver of a piece of wood in a crack on a round and holds it perfect.


----------



## luckydad (Feb 20, 2015)

You got that phone prop made yet ?? We be waiting !! )


----------



## fordf150 (Feb 20, 2015)

Poleman said:


> Whats your elevation?? I'm at 4000ft and have to compensate. A 150 lb reading would be around 170 sea leavel. Use to drive me nuts trying to figure out how everyone else was getting such good and higher readings!!



rubbin it in a little. this is my stock 7900

checked elevation here. 806ft


----------



## cuttinties (Feb 20, 2015)

LegDeLimber said:


> Do you still have that resonant chamber from inside of the muffler?
> If so, could you measure the volume of it?
> Would prefer in CCs if you have something like an oil ratio cup.
> Looks like you could hold it like I rotated your pic and depending on how wide,
> ...


I think a guy should look at that chamber a little closer on the next one. There's another popular saw on the market right now that works off of a similar principal in stock form.


----------



## LegDeLimber (Feb 20, 2015)

And please turn phone sideways, for videoing!!!
Looking at skinny vids sucks.

and it's also a lil bit like looking through keyhole
and I'm not much into looking in a keyhole at another guy 
even IF he is running a bodacious saw.
Sorta wierds me out.


----------



## MillerModSaws (Feb 20, 2015)

Well I got some vids. If i can figure out how to get them from my phone to you well be golden.


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## MillerModSaws (Feb 20, 2015)

1030 ft is my elevation.


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## MillerModSaws (Feb 20, 2015)

When I tuned this saw I just buried in the biggest piece of oak I had. I set it extremely rich and then dogged in the saw with just a nice pull on the handle and adjusted it till it quite four stroking. Still has pretty fat so leaned it out just a scotch more. I can tell you the stock saw likes to run right around 10300. This one likes 12200.


----------



## Mastermind (Feb 20, 2015)

I rarely watch videos Carl........I'm gonna make an exception for this one sir. 

Looking forward to seeing it.


----------



## komatsuvarna (Feb 20, 2015)

MillerModSaws said:


> Well I got some vids. If i can figure out how to get them from my phone to you well be golden.



upload them from your phone straight to youtube...then just copy and paste the link here. That's been the quickest and easiest for me.


----------



## Mastermind (Feb 20, 2015)

I have to save em in the puter......then upload.....then link....

Damn.......I'm old.


----------



## MillerModSaws (Feb 20, 2015)

Well I got one vid uploaded to something. I've tried the you tube thing. Got it to work on a short vid but not anything over 30 sec. I'm gonna take my lovely wife to supper than see what I can do.


----------



## Knobby57 (Feb 20, 2015)

The wait is killing me!! Hurry hurry hurry [emoji41]


Sent from my iPhone using Tapatalk


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## Mastermind (Feb 20, 2015)

Family first my friend.


----------



## redoakman (Feb 20, 2015)

MillerModSaws said:


> Well I got one vid uploaded to something. I've tried the you tube thing. Got it to work on a short vid but not anything over 30 sec. I'm gonna take my lovely wife to supper than see what I can do.


Sender my way when u get back . have fun .


----------



## Hedgerow (Feb 20, 2015)

Mastermind said:


> I have to save em in the puter......then upload.....then link....
> 
> Damn.......I'm old.


Older than me...
That, I'm glad of....


----------



## gritz (Feb 20, 2015)

Yeah, pretty excited about how it turned out. You'll have to bring it on the 28th so we can play........


----------



## WKEND LUMBERJAK (Feb 20, 2015)

gritz said:


> Yeah, pretty excited about how it turned out. You'll have to bring it on the 28th so we can play........


Key word is work with. I bet we can break it in bucking logs.


----------



## Poleman (Feb 20, 2015)

fordf150 said:


> View attachment 405543


----------



## gritz (Feb 20, 2015)

WKEND LUMBERJAK said:


> Key word is work with. I bet we can break it in bucking logs.



Yeah, sorry, I meant work, lol. I should be more careful about my Freudian key slips......


----------



## Mastermind (Feb 20, 2015)

Work is a four letter word.


----------



## MillerModSaws (Feb 20, 2015)

Vids on youtube. Know to get them here. Lol


----------



## Mastermind (Feb 20, 2015)

Very Nice !!!!!!


----------



## MillerModSaws (Feb 20, 2015)




----------



## MillerModSaws (Feb 20, 2015)

Mastermind said:


> Very Nice !!!!!!



Thank u. I'm struggling here. Lol. Thank you for posting that.


----------



## MillerModSaws (Feb 20, 2015)

Who's got the stop watch. Have not put any times together yet.


----------



## Mastermind (Feb 20, 2015)

Who needs a stopwatch. That beast is bad ass.


----------



## MillerModSaws (Feb 20, 2015)

Mastermind said:


> Who needs a stopwatch. That beast is bad ass.


I was super impressed. I love the wide power band. You can pull this saw way down and it still hogs away. It's hard to explain other than it has excellent chain speed and does not require a light hand.


----------



## Poleman (Feb 20, 2015)

I agree Randy.....NICE....VERY NICE!!!!!!!


----------



## Mastermind (Feb 20, 2015)

I was at one of of Terry's GTGs a year or two ago....someone fired up a 7900 and dropped it in a log, and I could tell it was turning at least 1000 RPM faster in the cut than any saw I brought. Heck, I thought my 372 was mean, but this 7900 would chew it up and spit it out....

Never have I found a stronger/faster/just meaner saw than a well built 7900/10


----------



## MillerModSaws (Feb 20, 2015)

Mastermind said:


> I was at one of of Terry's GTGs a year or two ago....someone fired up a 7900 and dropped it in a log, and I could tell it was turning at least 1000 RPM faster in the cut than any saw I brought. Heck, I thought my 372 was mean, but this 7900 would chew it up and spit it out....
> 
> Never have I found a stronger/faster/just meaner saw than a well built 7900/10


I'm can't argue. Will a 7900 coil work on this saw. The thing is so close to rev limiter I'm afraid to lean it out anymore. Lol. Another 500 rpm maybe the ticket. 12500 on 7910 and 13000 on 7900 correct?


----------



## Mastermind (Feb 20, 2015)

I'm not 100% Carl. Heck, I'd try it. 

Are the flywheels the same part number? If so the coils should swap.


----------



## MillerModSaws (Feb 20, 2015)

Mastermind said:


> I'm not 100% Carl. Heck, I'd try it.
> 
> Are the flywheels the same part number? If so the coils should swap.


Good question. I will look that up.


----------



## Mastermind (Feb 20, 2015)

This stuff is fun ain't it?


----------



## awol (Feb 20, 2015)

A cheap Chinese 272 Husky coil works on a 7900 with a little ingenuity.


----------



## MillerModSaws (Feb 20, 2015)

Mastermind said:


> This stuff is fun ain't it?


Hell ya. And the flywheels are the same! Bam.


----------



## MillerModSaws (Feb 20, 2015)

If any of you were wondering that is oak. And frozen oak at that. Lol.


----------



## fordf150 (Feb 20, 2015)

Early higher rpm coil is differentand also NLA.not sure if they interchange. Dolmar says that they don't and if you need to replace the early coil that you must replace coil and flywheel as a set. This is all based on memory. I posted the tech bulletin in nnero's 7900 thread I think


----------



## MillerModSaws (Feb 20, 2015)

fordf150 said:


> Early higher rpm coil is differentand also NLA.not sure if they interchange. Dolmar says that they don't and if you need to replace the early coil that you must replace coil and flywheel as a set. This is all based on memory. I posted the tech bulletin in nnero's 7900 thread I think


Thank you. I just know I pulled the part numbers and they where the same.


----------



## tickbitintn (Feb 20, 2015)

dang that thing sounds good, holds easily noticeable higher rpm and never bogs in the slightest.

well u suck....  cause now i want one of those... 

nice work and thanks for the thread !!


----------



## MillerModSaws (Feb 20, 2015)

tickbitintn said:


> dang that thing sounds good, holds easily noticeable higher rpm and never bogs in the slightest.
> 
> well u suck....  cause now i want one of those...
> 
> nice work and thanks for the thread !!


It ain't over yet. We still got one more saw to play with. Lol.


----------



## fordf150 (Feb 20, 2015)

MillerModSaws said:


> Thank you. I just know I pulled the part numbers and they where the same.


When your looking at the 7900 ipl it shows the later coil and flywheel in the big picture but in the upper corner it shows early model which is the higher rpm coil....this is my understanding of it anyway...the coils are color coded too....talk to 166 he had some knowledge I didn't last time we went through this Because seems to me I am forgetting something


----------



## tickbitintn (Feb 20, 2015)

MillerModSaws said:


> It ain't over yet. We still got one more saw to play with. Lol.



can't wait will be following for sure.
keep up the good work.


----------



## cgraham1 (Feb 21, 2015)

MillerModSaws said:


> I'm can't argue. Will a 7900 coil work on this saw. The thing is so close to rev limiter I'm afraid to lean it out anymore. Lol. Another 500 rpm maybe the ticket. 12500 on 7910 and 13000 on 7900 correct?


I believe the 7900 is limited at 13,500, and the 7910 is 12,900. Here's my stock 7900...


----------



## Mastermind (Feb 21, 2015)

Well done men.......high fives all around !!!!



I'm going to bed.


----------



## LegDeLimber (Feb 21, 2015)

Danged impressive! Putting the wood in the wind.

Anyone ever take a magnet or compass and check the polarity on these flywheels?
Of course You'd need to check both flywheels in order to know of any difference.
And I'm talking about any flywheel or coil swap also, no matter what unit.


----------



## Knobby57 (Feb 21, 2015)

That thing is laughing at that oak tree[emoji41] 


Sent from my iPhone using Tapatalk


----------



## drf255 (Feb 21, 2015)

Great job Millermods. That saw is one mean MOFO.

Never heard of the model before. How many CC's?

Damn that saw is crazy fast.


----------



## cgraham1 (Feb 21, 2015)

drf255 said:


> Never heard of the model before. How many CC's?


79cc


----------



## wigglesworth (Feb 21, 2015)

Best build thread I've seen in a long time. ...


----------



## KG441c (Feb 21, 2015)

Very Nice!!


----------



## gritz (Feb 21, 2015)

MillerModSaws said:


>






Mastermind said:


> Very Nice !!!!!!




Based on my stopwatch, the stock cuts were at, 27, 23, and 25 seconds for an average of 25 seconds per cut. The ported cuts were all right at 16 seconds. So you shaved off 9 seconds per cut on average, which my redneck math tells me is a 36% improvement over stock! Now you've got me thinking I need to find a couple saws to sell real quick! Great work!


----------



## Paragon Builder (Feb 21, 2015)

Sub'd


----------



## jar944 (Feb 21, 2015)

MillerModSaws said:


> I was super impressed. I love the wide power band. You can pull this saw way down and it still hogs away. It's hard to explain other than it has excellent chain speed and does not require a light hand.


 
Nice



fordf150 said:


> View attachment 405543
> rubbin it in a little. this is my stock 7900



Ha, seems tight. I had to go check my stock 7900 after seeing that, its only 200.



fordf150 said:


> Early higher rpm coil is differentand also NLA.not sure if they interchange. Dolmar says that they don't and if you need to replace the early coil that you must replace coil and flywheel as a set. This is all based on memory. I posted the tech bulletin in nnero's 7900 thread I think



From my research the red top 7900 black coil and black top 7900 burgundy coils have the same rpm limit. I believe either set would fit the 7910.


----------



## blsnelling (Feb 21, 2015)

Very, very nice work! That saws sounds fantastic in the cut!


----------



## fordf150 (Feb 21, 2015)

here is the tech bulletin on the 7900 coils for anyone interested. 

posted by 166 on chainsaw repair.."I have five 7910's running on 7900 red coils with no issues. Two are stock saws with the SLR muffler and three are ported with the old style 7900 muffler."
13,500 limited 


I knew i was forgetting something and at home on the phone its to slow and painful to search for information


----------



## ft. churchill (Feb 21, 2015)

MillerModSaws said:


> View attachment 404808
> And here's a pic I will prob catch crap over. I am the first to admit I have a lot to learn but here I know the air and gas mix is in a gas form not a liquid but I like to run them under the faucet to try to understand how the trans are flowing. This one in particular the exhaust side trans I may pull the the edge closet to the exhaust a little more straight out on the next build. But like I said this is more me learning how each cylinder flows. And the directions my port work is aiming. On the port you see flowing. Both sides were head towards the intake when I started and you can see how I pulled the middle of the port around just a bit towards the center of the piston.



I do the same thing with the water, also with carb cleaner in the spray can, when I'm cleaning up the chips from grinding, before I lower the jug back onto the piston for more measuring.


----------



## Paragon Builder (Feb 21, 2015)

WOW! That saw really rips!!! Very nice work!!!


----------



## ft. churchill (Feb 21, 2015)

Based on my stopwatch, the stock cuts were at, 27, 23, and 25 seconds for an average of 25 seconds per cut. The ported cuts were all right at 16 seconds. So you shaved off 9 seconds per cut on average, which my redneck math tells me is a 36% improvement over stock!

I love rednecked math.. Another thing to notice beyond just timed cuts is how consistent the timed cuts are on the ported saw. The stock saw had as much as a 4 second variation in cut speed, the ported was almost unmeasurable in diference. Bottom line is that the port job made that saw easier to cut with and keep on top of the big, fat powerband.


----------



## shorthunter (Feb 21, 2015)

mdavlee said:


> I use my phone propped on something any more.



Me too. A hardwood cookie with a cut halfway across the center works pretty good. You can set the phone in the kerf and the cookie will sit on anything flat.


----------



## shorthunter (Feb 21, 2015)

MillerModSaws said:


> When I tuned this saw I just buried in the biggest piece of oak I had. I set it extremely rich and then dogged in the saw with just a nice pull on the handle and adjusted it till it quite four stroking. Still has pretty fat so leaned it out just a scotch more. I can tell you the stock saw likes to run right around 10300. This one likes 12200.



Are we talking in the wood? The stock saw sounds rich in the cut


----------



## MillerModSaws (Feb 21, 2015)

shorthunter said:


> Are we talking in the wood? The stock saw sounds rich in the cut


I only tuned the ported one. Both saws would 4 stroke as soon as you lifted pressure. I will not argue on the stock saw as I put gas and oil in it and ran it.


----------



## Paragon Builder (Feb 21, 2015)

shorthunter said:


> Me too. A hardwood cookie with a cut halfway across the center works pretty good. You can set the phone in the kerf and the cookie will sit on anything flat.


I'm always trying to get my phone to stay propped up. That's a great idea! 
What's a hardwood cookie?? Lol


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## CR500 (Feb 21, 2015)

I think I could really use a 7900/10.... may have to big bore a 6400 but none the less these saws are grabbing my attention as of late 

Sent from my non internal combustion device.


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## Paragon Builder (Feb 21, 2015)

So on this next saw what do you think of doing things a bit different?
Tune the stock saw to your best standards and video.
Then muffler mod, retune and video.
Then port, retune and video.
This way we can see the benefits of the different stages. 
Of course the ultimate goal here is to achieve the best possible work saw. And the first saw certainly looks like a winner. Can't wait to see what the second one turns out like!


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## 166 (Feb 21, 2015)

fordf150 said:


> When your looking at the 7900 ipl it shows the later coil and flywheel in the big picture but in the upper corner it shows early model which is the higher rpm coil....this is my understanding of it anyway...the coils are color coded too....talk to 166 he had some knowledge I didn't last time we went through this Because seems to me I am forgetting something



'01 - '03 64/73/7900's had the black coil which is limited to 13,500. The Red Coil came out during the 2004 built saws which was to work with the heated handle models. The red coil saws run better than the black coil but there was a flywheel change at the same time. 



shorthunter said:


> Are we talking in the wood? The stock saw sounds rich in the cut





MillerModSaws said:


> I only tuned the ported one. Both saws would 4 stroke as soon as you lifted pressure. I will not argue on the stock saw as I put gas and oil in it and ran it.



The stock saw in that video is probably a 1000 rpm rich.

Listen to the sound of this saw at the 9 second mark.


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## MillerModSaws (Feb 21, 2015)

Paragon Builder said:


> So on this next saw what do you think of doing things a bit different?
> Tune the stock saw to your best standards and video.
> Then muffler mod, retune and video.
> Then port, retune and video.
> ...


I'm going to start with a lower exhaust and maybe some more blowdown. But we'll see were it goes and what suggestions come across the board.


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## Hedgerow (Feb 22, 2015)

You guys are gonna run the price of 7900's up...


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## Hedgerow (Feb 22, 2015)

MillerModSaws said:


> I'm going to start with a lower exhaust and maybe some more blowdown. But we'll see were it goes and what suggestions come across the board.


Finally got half the vid to load out here in the sticks..
Sounds good..
Real good..


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## Hinerman (Feb 22, 2015)

Hedgerow said:


> Finally got half the vid to load out here in the sticks..
> Sounds good..
> Real good..



It is singing real good .....Subbed


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## MillerModSaws (Feb 23, 2015)

Gor started on the second saw tonight. Intake squared up and a little roughing on the exhaust. Don't wanna get carried away till I get the squish and base cut. Going to cut it the same as the other saw. I thought this saw was running pretty rich but the plug shows it wasn't to bad.


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## MillerModSaws (Feb 24, 2015)

Ok it's coming together slowly. Lol. I'm doing 105/135 on this saw to start a lower exhaust with more blow down. Here's a pic of what I need to remove. Taking .030 off base puts your trans almost right there. So I'm just going to do a flat 135. And square up the corners.


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## MillerModSaws (Feb 24, 2015)

Intake and exhaust done. Trans are almost done. Have just a little fine tuning to do on them. Exhaust flange port matched. Muffler is modded just like the first one but still needs port matched to exhaust.


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## Paragon Builder (Feb 25, 2015)

Any predictions??


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## MillerModSaws (Feb 25, 2015)

Paragon Builder said:


> Any predictions??


Slower but you will be able to dawg the saw in and pull it around with a lot more force. But that's running off experience with a 372xp. Lol. Who knows on this freak of nature. I know if it's faster there's a lot less work in this recipe.


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## MillerModSaws (Feb 25, 2015)

Although right now the most time is spent on the exhaust port. Lots of work on this saw and the muffler mod is time consuming to uncrimp remove the SLR yada yada. Lol


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## MillerModSaws (Feb 25, 2015)

I didn't go back threw the thread but back there somewhere someone wanted more pics of the SLR. Here they are before I hack the flange off of it to put back in the muffler for support and spacing. He also wanted cc measurements. I will try and get that.


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## wigglesworth (Feb 25, 2015)

MillerModSaws said:


> I didn't go back threw the thread but back there somewhere someone wanted more pics of the SLR. Here they are before I hack the flange off of it to put back in the muffler for support and spacing. He also wanted cc measurements. I will try and get that.



What a dang contraption....


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## ELECT6845 (Feb 25, 2015)

Very nice work. I sold a few saw so I might have to try one of these fancy Dolmars. I like.


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## MillerModSaws (Feb 25, 2015)

wigglesworth said:


> What a dang contraption....


Agreed but when removed it's just like an old saw before strato.


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## Paragon Builder (Feb 25, 2015)

What's its purpose?


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## Mastermind (Feb 25, 2015)

Paragon Builder said:


> What's its purpose?



I'm not 100% sure.....but I think it gets really hot, and burns off hydrocarbons in the exhaust. 

A lot of the work in this build is getting rid of it though.


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## jar944 (Feb 25, 2015)

Paragon Builder said:


> What's its purpose?



My guess is its helping keep the fresh charge in the cylinder and not letting it out the sneak out exhaust. look at it like a tuned pipe and you can see what I'm talking about.


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## MillerModSaws (Feb 25, 2015)

Mastermind said:


> I'm not 100% sure.....but I think it gets really hot, and burns off hydrocarbons in the exhaust.
> 
> A lot of the work in this build is getting rid of it though.


Welcome back. Hope all is well down in your neck of the woods.


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## Mastermind (Feb 25, 2015)

I've thought about that too.....but just ain't buying it. I really think it's about emissions....


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## Mastermind (Feb 25, 2015)

MillerModSaws said:


> Welcome back. Hope all is well down in your neck of the woods.



We survived......and the shop is finally warmed back up.


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## Tractorsaw1 (Feb 25, 2015)

Can these 7910's do anything a 7900 can't? Sorry I don't know enough about them other than you can't get them as cheap as the 7900's were. But this thread makes me want to get a 7900 to open up. 

Nice work Carl


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## jar944 (Feb 25, 2015)

Mastermind said:


> I've thought about that too.....but just ain't buying it. I really think it's about emissions....



Its a Helmholtz chamber, so I cant see it just being used to get hot and burn off emissions.

Think of it this way. 

During initial blowdown a portion of the exhaust is going out the hole in the bottom of the resonant chamber, the remaining exhaust that cant make it out the port is filling up the lower pressure "closed" portion of the chamber. Blow down continues, the closed chamber reaches pressure equilibrium and now all flow is out the port in the chamber .

Ideally the pressure in the chamber (at the exhaust port) remains equal or slightly lower to the pressure in the cylinder while the transfers and exhaust port are closing while the closed portion is bleeding off the pressure it gained during blowdown


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## fordf150 (Feb 25, 2015)

It is just a fancy way of stuffing the exhaust up so that fresh mix doesnt escape out the exhaust was always my thought of what it did just looking at it but @jar944 knows more than me and after reading what a Helmholtz chamber was i am rethinking how it works and its effects

In some two-stroke engines, a Helmholtz resonator is used to remove the need for a reed valve. A similar effect is also used in the exhaust system of most two-stroke engines, using a reflected pressure pulse to supercharge the cylinder (see Kadenacy effect.) http://en.wikipedia.org/wiki/Helmholtz_resonance


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## Mastermind (Feb 25, 2015)

Good stuff........

It's a good day........cause I learned something new.


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## MillerModSaws (Feb 25, 2015)

Mastermind said:


> Good stuff........
> 
> It's a good day........cause I learned something new.


X2. I'm going to haft to reaserch this helm Holtz chamber. But if it's acting like a piped saw. Would that explain the shorter blowdown in the 7910 over the 7900? Good thread guys keep it up!


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## jar944 (Feb 25, 2015)

fordf150 said:


> It is just a fancy way of stuffing the exhaust up so that fresh mix doesnt escape out the exhaust was always my thought of what it did just looking at it but @jar944 knows more than me and after reading what a Helmholtz chamber was i am rethinking how it works and its effects
> 
> In some two-stroke engines, a Helmholtz resonator is used to remove the need for a reed valve. A similar effect is also used in the exhaust system of most two-stroke engines, using a reflected pressure pulse to supercharge the cylinder (see Kadenacy effect.) http://en.wikipedia.org/wiki/Helmholtz_resonance



ha, Nice that pic would have saved me some typing.


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## gritz (Feb 25, 2015)

Seems like there needs to be some tinkering with this SLR thing? I would be curious to see two things. The first is the exact difference between running a stock saw with or without it (leaving the opening in the muffler outlet the same size) , the second is running a ported saw with or without it. Then if it helps a stock saw, but hinders a ported saw, it would be nice to see if the SLR and exhaust outlet were enlarged to accommodate more airflow on a ported saw to see if it helped or hindered the saw.


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## Mastermind (Feb 25, 2015)

So.......is this a performance enhancement, or just a emissions device? Is the volume of the chamber sized for a stock saw? If so, will it be too small for the output after mods?


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## MillerModSaws (Feb 25, 2015)

I have hacked this SLR unit up already but early I was asked how much will it hold. If you hold it with the chamber down and fill it till it hits the exhaust hole it holds 69 ml. So that would be 69cc.


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## jar944 (Feb 25, 2015)

Mastermind said:


> So.......is this a performance enhancement, or just a emissions device? Is the volume of the chamber sized for a stock saw? If so, will it be too small for the output after mods?



strictly emissions/fuel economy. Though correctly sized it shouldn't hinder performance. 

Its not functioning like a performance pipe. Its just there to "shut the door" on the exhaust port.


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## fordf150 (Feb 25, 2015)

honestly i cant tell the difference when they are removed from a stock saw running a 20" bar but the PC-7414 has the same thing and removing it plus adding a second outlet to the muffler really wakes those up when cutting arbor deep in concrete


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## Mastermind (Feb 25, 2015)

jar944 said:


> strictly emissions/fuel economy. Though correctly sized it shouldn't hinder performance.
> 
> Its not functioning like a performance pipe. Its just there to "shut the door" on the exhaust port.



Well........thanks for the lessons. I'm always tickled to learn.


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## LegDeLimber (Feb 25, 2015)

I see that some of you guys are,
finally, 
waking up to that pulse chamber and how it works.

Stopping the flow out of the exhaust, is stopping the flow, is stopping the flow....
you won't likely be able to tune for an extraction,
But,
You can use that thing to stop the charge loss from a slightly wilder porting idea.
I'd say you might find a narrow spot, oh maybe 60~100 rpms wide 
that the chamber would
expel a pressure wave that you could exploit.

tangential thought?
Grab a copy of some software for figuring speaker cabinets, plus one for room acoustics
and go from there. 
Have fun fellers!!

going wild on the thinking for a second here:
Hmm, maybe open the top of the exhaust a pinch earlier and see if the gas rushing out 
carries enough inertia to give slight pull on the incoming charge. 
Now use that chamber to staunch the flow, when it kicks back the stallout/stoppage of flow or is it a positive wave with reversed/back flow?
Again though this will only hit on a narrow assed frequencey band, that might be exploited.
Nasty, skinny spike in the power curve though.
It obviously works well enough to keep the unburned charge losses in check.

Keep asking yourselves 
how !!

oh and don't forget about boost bottles concepts, just move it over to the exhaust stream thoughts.
I.E. http://www.superstreetonline.com/how-to/engine/modp-1102-motordyne-tuning-test-pipes/


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## Paragon Builder (Feb 25, 2015)

My head is spinning!!


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## LegDeLimber (Feb 25, 2015)

and The shrinks have been trying to medicate that spin energy outta me , for the last 45 years!
ahhhaahahhaaa!!


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## MillerModSaws (Feb 25, 2015)

Saw no. 2 back together. Numbers are 105/135/80. It's snowing and blowing here but maybe able to talk my wife into going and getting some numbers when she gets home. Was hoping my bar adapter would show today so I could run my longer stihl bars but it didnt. Lol.


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## MillerModSaws (Feb 26, 2015)

Well boys here she is. The saws are so close I'm gonna haft to move to a longer bar in bigger wood. But as you will see this saw pulled a 14 sec time. Not sure where to go from here. Lol.


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## MillerModSaws (Feb 26, 2015)

I cut wood for a couple hours with my 375xp which I really like that saw too. It's a little lighter but it won't run with these boys. I'm shocked that with that big a difference in the numbers there's not an obvious difference in the way they run. Like I said. Hoping it will show with a bigger bar in bigger wood. Both saws need fine tuned. I am going to leave them just like they are and take them to the charity cut and get some opinions. Lol.


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## MillerModSaws (Feb 26, 2015)

So that being said both these saws run great compared to the stock saw. But first test I'm not super close to a final set of numbers.


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## fin460 (Feb 26, 2015)

and to think, these saws aren't broken in yet....


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## redoakman (Feb 26, 2015)

MillerModSaws said:


> I cut wood for a couple hours with my 375xp which I really like that saw too. It's a little lighter but it won't run with these boys. I'm shocked that with that big a difference in the numbers there's not an obvious difference in the way they run. Like I said. Hoping it will show with a bigger bar in bigger wood. Both saws need fine tuned. I am going to leave them just like they are and take them to the charity cut and get some opinions. Lol.


you can send me one free and i will let you now in a few years lmao


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## Paragon Builder (Feb 27, 2015)

So what are your thoughts as compared to a ported 460/461????


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## WKEND LUMBERJAK (Feb 27, 2015)

Carl are you bringing these the the charity cut in KCMO Sat I can provide a 24 ,28 or a 34" bar for testing let me know.


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## MillerModSaws (Feb 27, 2015)

WKEND LUMBERJAK said:


> Carl are you bringing these the the charity cut in KCMO Sat I can provide a 24 ,28 or a 34" bar for testing let me know.


 I have a 24 and 28 but my next bar is a 36. I think gritz is bringing a 30. If you could bring the 34 well give it a couple slices. We won't run it much I just want to see if I can make these numbers pop.


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## Poleman (Feb 27, 2015)

It's very interesting on two saws built differently run similar....I think your doing the right thing in testing/comparing in bigger wood. They both undoughtably run good but now to find each saws nitch. In building saws you could offer two types of builds for what type of use the saw will mostely see......thats pretty cool!!!!

I think the Dolmars are way underratted for what they can do stock and what they can do moddified.


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## MillerModSaws (Feb 27, 2015)

I talked to randy last night and while I'm going to nail this saw down a little more. I think he is on to something. As the exhaust & trans are very important. But from just intial testing It maybe the intake height and just the opening up of this saw that's the ticket. Like I said this is just initial thought. More testing will tell. I am interested to get the bigger bars on these as I do feel it will open the numbers up a bit. Then the question will be. Is it the exhaust height or the blow down. I can tell you both of these saws even ported this far apart are awesome.


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## gritz (Feb 28, 2015)

MillerModSaws said:


> I have a 24 and 28 but my next bar is a 36. I think gritz is bringing a 30. If you could bring the 34 well give it a couple slices. We won't run it much I just want to see if I can make these numbers pop.



Yep, and we'll make a little exodus over to where that huge locust is that I cut a couple weeks ago. It will give those bad boys a workout for sure!


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## Hedgerow (Mar 1, 2015)

Ran both saws yesterday...
Both ran great.. 
But if we're voting, version #1 was my favorite.. 
Anyone that had either of those saws would be proud as peacocks of em..


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## Paragon Builder (Mar 1, 2015)

So what was the biggest difference to you? Speed? Torque?


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## Hedgerow (Mar 1, 2015)

One had a dull chain, and the other was better...


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## redoakman (Mar 1, 2015)

dam dull chains lol


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## MillerModSaws (Mar 1, 2015)

Someone (me) needs chain sharpening lessons. Lmao. I watched hedgerow run saw 2 with a 32" bar and saw saw 1 with jacked 28" and a good 24". Not sure his opinion but it will pull a 32" but I would say the 24 or 28 combo is where it's at for this saw. I have 1 more saw on its way to throw into the mix I am going to put 103 with 30 bd in it and compare. Drop saw 2 to 105 with 28 bd. Depending on what I see there I will decide what works best for me. Then I will play with advancing the timing just a bit. Then we should have some final numbers. But i agree with hedgerow. I would not be afraid to send either of these saws to a customer. Unless there gonna run them against hedgerows 7900. Lol.


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## mdavlee (Mar 1, 2015)

I think you 105 is too low exhaust to me for a 79cc saw. The higher the exhaust the more blowdown they seem to like.


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## MillerModSaws (Mar 1, 2015)

mdavlee said:


> I think you 105 is too low exhaust to me for a 79cc saw. The higher the exhaust the more blowdown they seem to like.


I agree but I'm always open for suggestions and brad suggested I try 105. So I did. The thing is with 105/30 I can change it now to whatever I want. The 102/27 saw is set. Lol. If it ends up being the saw of choice all 3 saws will be set to that but I rally wanna play with that bd number.


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## Paragon Builder (Mar 1, 2015)

Hedgerow said:


> One had a dull chain, and the other was better...


Nothing like a dull chain to frustrate you! 
Or did it just "feel" like a dull chain???
After using the "better" saw of course???[emoji6]


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## Hedgerow (Mar 1, 2015)

MillerModSaws said:


> I agree but I'm always open for suggestions and brad suggested I try 105. So I did. The thing is with 105/30 I can change it now to whatever I want. The 102/27 saw is set. Lol. If it ends up being the saw of choice all 3 saws will be set to that but I rally wanna play with that bd number.


I liked the 102 saw.. 
No question they'll run a bigger bar than they will oil...


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## wigglesworth (Mar 1, 2015)

What's a Dullmar™?


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## fin460 (Mar 1, 2015)

dang you already trademarked it


wigglesworth said:


> What's a Dullmar™?


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## MillerModSaws (Mar 1, 2015)

Definition of dullmar- excellent running ported saw that is put to shame by a crappy azz chain sharpening job.


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## redoakman (Mar 1, 2015)

MillerModSaws said:


> Definition of dullmar- excellent running ported saw that is put to shame by a crappy azz chain sharpening job.


do i need to come show ya how to file lol


----------



## shorthunter (Mar 1, 2015)

Hedgerow said:


> I liked the 102 saw..
> No question they'll run a bigger bar than they will oil...



I want more out of my 102/29


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## Hedgerow (Mar 1, 2015)

shorthunter said:


> I want more out of my 102/29


How much comp did you end up with?


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## shorthunter (Mar 1, 2015)

170ish with squish around 19


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## MillerModSaws (Mar 1, 2015)

shorthunter said:


> I want more out of my 102/29


I will be working down to that. One of the last things I will do is set one of these at 27 bd and 1 at 30 bd same exhaust to see what they like.


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## MillerModSaws (Mar 1, 2015)

shorthunter said:


> 170ish with squish around 19


Both of these are running 200 comp with intake at 80.


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## Laslabjohn (Mar 1, 2015)

MillerModSaws said:


> Someone (me) needs chain sharpening lessons. Lmao. I watched hedgerow run saw 2 with a 32" bar and saw saw 1 with jacked 28" and a good 24". Not sure his opinion but it will pull a 32" but I would say the 24 or 28 combo is where it's at for this saw. I have 1 more saw on its way to throw into the mix I am going to put 103 with 30 bd in it and compare. Drop saw 2 to 105 with 28 bd. Depending on what I see there I will decide what works best for me. Then I will play with advancing the timing just a bit. Then we should have some final numbers. But i agree with hedgerow. I would not be afraid to send either of these saws to a customer. Unless there gonna run them against hedgerows 7900. Lol.


She's headed your way in the morning!


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## MillerModSaws (Mar 1, 2015)

Laslabjohn said:


> She's headed your way in the morning!


Awesome!


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## MillerModSaws (Mar 3, 2015)

I got saw 2 tore down boys so hopefully I won't bore you guys too much. Saw 3 is headed in I'm gonna play with the numbers just a bit before it gets here but I at this point 102/?/80 is what seems to be the trick. The ? Is what we need to find. Between the 3 saws I will hopefully end up with a 27,28,29 blowdown. See if we can narrow down that blowdown.


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## Paragon Builder (Mar 3, 2015)

Your not gonna bore us! Nice to see this experimentation!!!


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## MillerModSaws (Mar 3, 2015)

Ok thought this visual may help. The exhaust now sits at 102. So from the roof of the exhaust to the bottom of the ring is 29 degrees blowdown. The ring is sitting at 131 degrees. I mark it with an ultra fine sharpie and grind the trans till the mark is almost gone. Finishing with Diamond burrs. Slowly but surely.


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## MillerModSaws (Mar 3, 2015)

Here's a roughed in pic. You can see I'm really close to my line. I will square the corners a bit more than finish with a diamond burr smoothing all the bumps out and checking with the ring till I get the ring edge and port edge to match. Then I will put a chamfer on all the corners. Not sure what happened to the above pic. If you can't see it holar and I'll repost it.


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## MillerModSaws (Mar 3, 2015)

Are the pics showing up. There not on my end. Lol.


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## ELECT6845 (Mar 3, 2015)

I see em


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## MillerModSaws (Mar 3, 2015)

Good deal. Thank you.


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## MillerModSaws (Mar 4, 2015)

Didn't get much done tonight. Had to go cut some wood. I had my 2 main saws listed on the trading post and now there headed to new homes. So I had to break out the old stockers. Lmao. I better hurry and get my hybrid done.


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## Deleted member 83629 (Mar 4, 2015)

MillerModSaws said:


> Someone (me) needs chain sharpening lessons. Lmao. I watched hedgerow run saw 2 with a 32" bar and saw saw 1 with jacked 28" and a good 24". Not sure his opinion but it will pull a 32" but I would say the 24 or 28 combo is where it's at for this saw. I have 1 more saw on its way to throw into the mix I am going to put 103 with 30 bd in it and compare. Drop saw 2 to 105 with 28 bd. Depending on what I see there I will decide what works best for me. Then I will play with advancing the timing just a bit. Then we should have some final numbers. But i agree with hedgerow. I would not be afraid to send either of these saws to a customer. Unless there gonna run them against hedgerows 7900. Lol.


file the rakers to .20 when you sharpen the chain


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## MillerModSaws (Mar 5, 2015)

Ok boys the results are in and I'm ready for your opinions. Remember I still have to mess with the timing. That said I ran the crap out of both saws tonight. I had to give saw 2 almost 1/4 more on the high needle after going to 102/131. But this us what I got. Both saws run super hard and I don't think you can go wrong with either but I started a crappy thread here a while back about torque vs chain speed and here's what I was after in that thread. Both saws would run a consistent 14-15 sec time in the wood.


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## MillerModSaws (Mar 5, 2015)

But i could tell a difference. The 27 bd saw liked 11800 in the wood but took a light hand to keep it there. The 29 bd saw hung out at 11400 but would hold that even better than the 27 bd saw would. So when I was racing them if you just let the saw run threw the wood the 27 bd would win. If you dawged in the 29 bd saw would win. And it seemed like you could pull the saw down a little further and it would recover nicer. All in all it is really hard for me to pick a winner cause they will both cut the wood in the same time it's all in how you run the saw. Please give me your opinions and thought.


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## MillerModSaws (Mar 5, 2015)

was a little heavy handed with it at first. Lol


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## Knobby57 (Mar 5, 2015)

Looks like 28 blowdown wins [emoji41]


Sent from my phone when I should be working


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## MillerModSaws (Mar 5, 2015)

Knobby57 said:


> Looks like 28 blowdown wins [emoji41]
> 
> 
> Sent from my phone when I should be working


Thats what I'm thinking. Maybe I can capture the middle but I'm intetested to see what everyone thinks.


----------



## shorthunter (Mar 5, 2015)

Knobby57 said:


> Looks like 28 blowdown wins [emoji41]
> 
> 
> Sent from my phone when I should be working



Pretty sure thats what Randy has been running for some time now


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## MillerModSaws (Mar 5, 2015)

shorthunter said:


> Pretty sure thats what Randy has been running for some time now


Hopefully he chimes in and gives his words of wisdom. But I'm gonna say the 28 does look like the ticket.


----------



## blsnelling (Mar 5, 2015)

Sounds fantastic. That saw runs like I like a saw to run. Kudos on all the hard work.


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## spindrift7mm (Mar 5, 2015)

I'd lean more toward torque for a general set of numbers as most guys are heavy handed. Nice job ! Ken


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## fin460 (Mar 5, 2015)

spindrift7mm said:


> I'd lean more toward torque for a general set of numbers as most guys are heavy handed. Nice job ! Ken


 
I agree with that, I've been running ported saws for some time now, and have been through plenty, but naturally I am ham fisted, and I suck at running saws in the top of their powerband. I hate a saw that I dawg in and I stall, even though it may be faster to a guy with experience.


----------



## fin460 (Mar 5, 2015)

I hate gas pickups, I have to have a diesel for the torque, lol.


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## MillerModSaws (Mar 5, 2015)

I have 1 more vid I will download later of the 27 bd and see what u think


----------



## fin460 (Mar 5, 2015)

I also grew up with people running 70cc saws with a 20", 60cc saws with a 18", and 50cc saws with a 16", we cut a lot of hedge!


----------



## bryanr2 (Mar 5, 2015)

fin460 said:


> I hate gas pickups, I have to have a diesel for the torque, lol.



AMEN to that!


----------



## redoakman (Mar 5, 2015)

MillerModSaws said:


> was a little heavy handed with it at first. Lol



the poor bur oak looks like a nice log . nice dolmar btw


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## MillerModSaws (Mar 5, 2015)

102/29/80(saw 1)


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## MillerModSaws (Mar 5, 2015)

redoakman said:


> the poor bur oak looks like a nice log . nice dolmar btw


I cut every bit of 20' of log in cookies tonight trying to decide which saw was the best. Lol.


----------



## blsnelling (Mar 5, 2015)

Have you played with intake duration at all? You could do that with a single sacrificial piston, but trimming the skirt length.


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## MillerModSaws (Mar 5, 2015)

blsnelling said:


> Have you played with intake duration at all? You could do that with a single sacrificial piston, but trimming the skirt length.


I have not played with it a lot no. Other than going from 76 to 80.


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## drf255 (Mar 6, 2015)

The 29 saw sounds better and appears to cut through the wood more effortlessly than the 27 saw, at least to me.


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## MillerModSaws (Mar 6, 2015)

drf255 said:


> The 29 saw sounds better and appears to cut through the wood more effortlessly than the 27 saw, at least to me.


Part of that is operator. Lol. Both saws have a sweet spot they like to run in. The 27 takes a bit lighter hand. It takes a few cuts to get adjusted to each saw. Lol. This operator tends to have a heavy hand.


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## KG441c (Mar 6, 2015)

MillerModSaws said:


> Part of that is operator. Lol. Both saws have a sweet spot they like to run in. The 27 takes a bit lighter hand. It takes a few cuts to get adjusted to each saw. Lol. This operator tends to have a heavy hand.


I know my buddy Laslab is chompin at the bits to get his!!! Lol!! Thoso saws look great!!!


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## MillerModSaws (Mar 6, 2015)

KG441c said:


> I know my buddy Laslab is chompin at the bits to get his!!! Lol!! Thoso saws look great!!!


Thank you! He won't haft to wait long! Lol.


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## lovetheoutdoors (Mar 6, 2015)

Good work, the saws look very strong in the video, way better than stock!


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## wigglesworth (Mar 6, 2015)

Ported saws are a fad....


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## LegDeLimber (Mar 6, 2015)

I dunno....
http://www.petrock.com/


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## wigglesworth (Mar 6, 2015)

LegDeLimber said:


> I dunno....
> http://www.petrock.com/



I was too poor growing up for fancy pets...


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## MillerModSaws (Mar 6, 2015)

Ok boys while I still have my ignition timing test to do both of these saws are getting close to done. I just wanna make sure I say thank you for all the support and tips I've got along the way. Both of these saws will be for sale as soon as I get the timing narrowed down. Fin460 has spoke for 1 of them but I'm going to ask $850 pho for the other one. They will have at most 3 tanks of fuel threw them. I thought i would offer it up to the guys following the thread first. Thank you. And we will get the timing hammered down and I'll let a few people like justin run them to get there opinions before they leave to there new owners.


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## MillerModSaws (Mar 6, 2015)

I hat unproductive nights. Was gonna hammer away on the timing and all my thread gauges are at work and I'll be dammed if I can figure out this bolt size. So I could pull the flywheel.


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## Knobby57 (Mar 6, 2015)

MillerModSaws said:


> I hat unproductive nights. Was gonna hammer away on the timing and all my thread gauges are at work and I'll be dammed if I can figure out this bolt size. So I could pull the flywheel.


 That looks like a machine screw more than a bolt 


Sent from my phone when I should be working


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## MillerModSaws (Mar 6, 2015)

Knobby57 said:


> That looks like a machine screw more than a bolt
> 
> 
> Sent from my phone when I should be working


I agree but it must be a metric machine screw which no place carries cause it ain't standard.


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## fin460 (Mar 6, 2015)

maybe you have, but atleast the photo shows that you haven't gotten pissed and used hammers and prybars yet


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## Knobby57 (Mar 6, 2015)

fin460 said:


> maybe you have, but atleast the photo shows that you haven't gotten pissed and used hammers and prybars yet


 I would have drilled it and tapped it to 6x1 


Sent from my phone when I should be working


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## redoakman (Mar 6, 2015)

They do this to us canadains . what really grinds my gears is when john Deere use both sets of measurement on all there tractors . drives me up the wall . but everything now a days is metric / imperial . yaaaahhhhh more tools ( more money down the drain ) .


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## MillerModSaws (Mar 6, 2015)

Knobby57 said:


> I would have drilled it and tapped it to 6x1
> 
> 
> Sent from my phone when I should be working


I can't d & t it cause those bolts hold the starter paws in. Lol.


fin460 said:


> maybe you have, but atleast the photo shows that you haven't gotten pissed and used hammers and prybars yet


Thats funny cause I called my tech line and ask the bolt size and the removal procedure is to put a thread cover on the crank and smack the end of the crank. I told them that ain't happening. Lmao.


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## Knobby57 (Mar 6, 2015)

Like silly Volvo 7mm Allen heads ??? 5.5 mm bolts . Just stupid . 
But I would be surprised if that has any SAE fasteners on it . Dolmar Probably has some special tool that's stupid $ like the STIHL seal puller that I find about worthless 


Sent from my phone when I should be working


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## Knobby57 (Mar 6, 2015)

MillerModSaws said:


> I can't d & t it cause those bolts hold the starter paws in. Lol.
> 
> Thats funny cause I called my tech line and ask the bolt size and the removal procedure is to put a thread cover on the crank and smack the end of the crank. I told them that ain't happening. Lmao.


 Never said I was smart . But at least it would be off lol.
Did you try heating the flywheel with a heatgun and giving it a pop with a piece of wood


Sent from my phone when I should be working


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## MillerModSaws (Mar 6, 2015)

Knobby57 said:


> Never said I was smart . But at least it would be off lol.
> Did you try heating the flywheel with a heatgun and giving it a pop with a piece of wood
> 
> 
> Sent from my phone when I should be working


No I'll wait and make bolts on Monday if I haft to.


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## fordf150 (Mar 6, 2015)

Socket over the crank snout and a couple taps with a hammer. Comes right off


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## CR500 (Mar 6, 2015)

redoakman said:


> They do this to us canadains . what really grinds my gears is when john Deere use both sets of measurement on all there tractors . drives me up the wall . but everything now a days is metric / imperial . yaaaahhhhh more tools ( more money down the drain ) .


Speaking from experience I agree....


Never can win haha
Sent from my non internal combustion device.


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## shorthunter (Mar 6, 2015)

MillerModSaws said:


> I can't d & t it cause those bolts hold the starter paws in. Lol.
> 
> Thats funny cause I called my tech line and ask the bolt size and the removal procedure is to put a thread cover on the crank and smack the end of the crank. I told them that ain't happening. Lmao.



That's how I remove all of my flywheels. Just need a good nut on the end of the crankshaft and a little sense


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## fin460 (Mar 7, 2015)

If its the saw that you have picked for me, use as big of a hammer you want


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## MillerModSaws (Mar 7, 2015)

fin460 said:


> If its the saw that you have picked for me, use as big of a hammer you want


I got them off and playing with the timing know. Hopefully I'll have then all done by tomorrow and ready for you to play with. If ya got time.


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## MillerModSaws (Mar 7, 2015)

Here's a pic of the flywheel. These with a built in key are really hard to measure and say remove .050 and you get 5°. So I'll show you how I do it. I remove from the side of the key the arrow points to so I can rotate the flywheel counter clockwise.


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## MillerModSaws (Mar 7, 2015)

I remove the flywheel then just sit it back on. I put my piston stop in and rotate the flywheel ccw till it hits then I mark tue flywheel and cases. Then you can remove the piston stop and mark the degrees you want using your degree wheel and then screw the piston stop back in and screw it in till you marks line back up. File the key until it lines up with your second mark. This is 6°. Roughly 7.5 mm between marks.


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## MillerModSaws (Mar 7, 2015)

Lots of ways to skin a cat on this one so don't get hung up on the little details. This one I actually was aiming for 5° but I marked the initial and filed it and then checked it and had hit 6°. Lol.


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## awol (Mar 7, 2015)

What has worked well for me when setting timing on these saws, is to remove the built-in key completely using a carbide bur, and use a degree wheel on the PTO side to record the movement. Take a baseline reading at the magnet/coil before disturbing.

Here is what happens at about 35° total advance, using a 272 unlimited coil.


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## Paragon Builder (Mar 7, 2015)

MillerModSaws said:


> Here's a pic of the flywheel. These with a built in key are really hard to measure and say remove .050 and you get 5°. So I'll show you how I do it. I remove from the side of the key the arrow points to so I can rotate the flywheel counter clockwise.


 I've never seen a rounded keyway like that before. Is the crank dimpled round like that too?


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## shorthunter (Mar 7, 2015)

awol said:


> What has worked well for me when setting timing on these saws, is to remove the built-in key completely using a carbide bur, and use a degree wheel on the PTO side to record the movement. Take a baseline reading at the magnet/coil before disturbing.
> 
> Here is what happens at about 35° total advance, using a 272 unlimited coil.
> View attachment 409528



She got a little hot


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## MillerModSaws (Mar 7, 2015)

Paragon Builder said:


> I've never seen a rounded keyway like that before. Is the crank dimpled round like that too?


No its just a normal key slot.


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## blsnelling (Mar 7, 2015)

A rounded key like that is not uncommon with the cast in keys. BTW, I don't worry about removing just the right amount. The taper is what locks it in place. So, I grind a little more than I need, put it in place with a degree wheel, and tighten the nut down.


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## MillerModSaws (Mar 8, 2015)

Ok boys got 1 more vid for ya. I've got the timing all worked out and this is mainly by feel. But i like the 5° advance. The 27° blowdown saw seemed to respond better than the 29° blowdown. They have better throttle response and seem to recover better when you bog them down. But here's the finial bid of saw 1 ready to go.


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## MillerModSaws (Mar 8, 2015)




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## Laslabjohn (Mar 8, 2015)

Mans thats a tough saw!!!


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## spencerpaving (Mar 8, 2015)

That saw is gettin err done!


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## Paragon Builder (Mar 8, 2015)

WOW! Just WOW!!


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## lovetheoutdoors (Mar 8, 2015)

That saw is running dang strong!


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## MillerModSaws (Mar 8, 2015)

I would like to thank everyone again for there participation in this thread. Hopefully there's some valuable info in here for you boys that wanna port your own saws. If not you know exactly what I'm gonna do to them if you send them my way or buy one from me. I have some catching up to do in the shop but hopefully we'll be on to the next model soon. I'm looking forward to it. Thanks again AS!!!


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## blsnelling (Mar 8, 2015)

Fantastic results! That saw sounds awesome. Good on ya!


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## MillerModSaws (Mar 8, 2015)

blsnelling said:


> Fantastic results! That saw sounds awesome. Good on ya!


Thank you. It's really hard for me to decide which one I like better. They both run awesome in my opinion and the difference is very very little. I took 2 guys that had no knowledge of what I had did to these 2 and let them run them today. One choose saw 1 the other choose saw 2 as there favorite. I think it's more of the one you adjust too first. Lol


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## spindrift7mm (Mar 8, 2015)

How bout long bar/big wood test, maybe check temp after 10 cuts. Great work !


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## ft. churchill (Mar 9, 2015)

I re-read the either thread, but what are the final numbers on the two different saws? What's your final impression after the timing changes? do you like the higher top end of the 27* saw, or the bigger torque band of the 29* saw. I know I'll wanna build one someday.


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## MillerModSaws (Mar 9, 2015)

It's a toss up. Final numbers were 102/129/80 and 102/31/80. I have one here I'm doing now and I will split the difference. And i think that will be the winner. Lol. 102/30/80. But there is very little difference in the 2. When cutting wood they will produce the same times. One can just be dawg a little harder.


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## ft. churchill (Mar 9, 2015)

Thank you very much. You have done some awesome developmental work on these saws.


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## Fly By Night (Mar 17, 2015)

Wow, I just read this whole thread. I have my 7900 apart on the bench now, this is just the thread I needed! I am so happy to FINALLY have someone sharing how to make these mysterious German innards even better. 

Have you tried polemans carb mods on these saws?

Also, what do you use to get in to open up the transfers like that?


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## MillerModSaws (Mar 17, 2015)

Fly By Night said:


> Wow, I just read this whole thread. I have my 7900 apart on the bench now, this is just the thread I needed! I am so happy to FINALLY have someone sharing how to make these mysterious German innards even better.
> 
> Have you tried polemans carb mods on these saws?
> 
> Also, what do you use to get in to open up the transfers like that?


The only mod I made on the carb was to slot the high needle so it didn't take a special wrench. I am gonna order a HD12 carb to try on one if that helps. Lol. And what are you meaning on the trans? How did I raise them.?


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## bryanr2 (Mar 17, 2015)

so is it worth tracking down a 7900 over a 7910 or not?


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## Poleman (Mar 17, 2015)

I think you'd get better results from modding the Zama. The HD will be a good carb but I didn't see the results as a warmed over Zama. The Zama will give the saw more bottom end from idle threw the power band and still feed fuel for the top end.

And on a ported saw like your it's turns the saw into a real beast....and there pretty unreal as your testing and videos show!!!


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## MillerModSaws (Mar 17, 2015)

bryanr2 said:


> so is it worth tracking down a 7900 over a 7910 or not?


I would go with a 7910. If you buy a 7900 and haft to replace p&c, coil, etc it's all gonna be 7910 stuff.


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## MillerModSaws (Mar 17, 2015)

Poleman said:


> I think you'd get better results from modding the Zama. The HD will be a good carb but I didn't see the results as a warmed over Zama. The Zama will give the saw more bottom end from idle threw the power band and still feed fuel for the top end.
> 
> And on a ported saw like your it's turns the saw into a real beast....and there pretty unreal as your testing and videos show!!!


Can u send me a link to your carb mod thread?


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## huskihl (Mar 17, 2015)

MillerModSaws said:


> Can u send me a link to your carb mod thread?


It just got bumped again today.
Dolmar 7900 carb upgrade. Last 3 or 4 pages
Haven't figured out how to paste links yet lol
Edit http://www.arboristsite.com/community/threads/dolmar-7900-carb-upgrade.229528/


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## fordf150 (Mar 17, 2015)

Rich/terry packed allot of testing and info into that thread!


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## huskihl (Mar 17, 2015)

Yes they did. Eyes are blurry and still have a headache


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## Poleman (Mar 17, 2015)

http://www.arboristsite.com/community/posts/5270301/

Here's the thread...pretty long but a lot of good info and how things were arrived at.

This wasn't my idea but was encouraged by Terry Syd and he feed me a lot of info to get me up to speed. From there it was just working things out.

I think there has been some unpublished upgrades that make the carb totally adjustable and adjust more like a stock carb and a lot more user friendly.

FYI these same mods can be used on the older 365/372 Huskys with the same results.

I need to slow down long enough to put my results and findings in a thread to share with those interested in doing the modding themselves. I think it would be a real help to builders like yourself.


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## Poleman (Mar 17, 2015)

Thanks Nate, I've about got things put together so I can put things all together with pic's and some explanations and tuning tips.....it will be a lot shorter than the original.....but there was a lot of ideas exchanged there and discussions that this all lead up to.

I will make a Cliff Note version!!!!! Ya listening Randy??


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## MillerModSaws (Mar 17, 2015)

Poleman said:


> http://www.arboristsite.com/community/posts/5270301/
> 
> Here's the thread...pretty long but a lot of good info and how things were arrived at.
> 
> ...


Awesome I will read it and look forward to seeing your results.


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## MillerModSaws (Mar 17, 2015)

Poleman said:


> Thanks Nate, I've about got things put together so I can put things all together with pic's and some explanations and tuning tips.....it will be a lot shorter than the original.....but there was a lot of ideas exchanged there and discussions that this all lead up to.
> 
> I will make a Cliff Note version!!!!! Ya listening Randy??


O hell ya I want the cliff note version. Lmao.


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## fordf150 (Mar 17, 2015)

MillerModSaws said:


> O hell ya I want the cliff note version. Lmao.


Yeah that thread will make the average persons eyes glaze over but even the results from where that thread ended are a great improvement over stock


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## Fly By Night (Mar 17, 2015)

MillerModSaws said:


> The only mod I made on the carb was to slot the high needle so it didn't take a special wrench. I am gonna order a HD12 carb to try on one if that helps. Lol. And what are you meaning on the trans? How did I raise them.?



How did you widen them/make the intake side go closer to the intake?


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## MillerModSaws (Mar 18, 2015)

Fly By Night said:


> How did you widen them/make the intake side go closer to the intake?


Those are not actually widened just cleaned up to the chamfers. But i use a right angle cc specialty tools grinder. 15sr kit is what I have. There are many ways. Dremel with cut off wheels, etc.


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## Fly By Night (Mar 18, 2015)

Does anyone have any idea how this port timing would work without milling the base of the jug? I don't have a mill to do so. Ive sharpened my lower transfers and cleaned up my intake/exhaust ports im tempted to square up the ports and call it a day.


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## MillerModSaws (Mar 18, 2015)

Fly By Night said:


> Does anyone have any idea how this port timing would work without milling the base of the jug? I don't have a mill to do so. Ive sharpened my lower transfers and cleaned up my intake/exhaust ports im tempted to square up the ports and call it a day.


IMO lathing the base and squish band is an important key to this formula. Don't get me wrong opening up the saw will help you out. But doing the squish band and base does 3 important things. It lowers your intake, gives you more comp which is important to the torque, and it gives your upper trans more time/area.


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## Poleman (Mar 18, 2015)

I liked that question and answer!! I think the Dolmars are a little more difficult to get the performance out of and a certain combination of steps to get there... I figured the cuts would help in timing changes and waking up the saw.....and does the combination ever wake them up!!!


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## Fly By Night (Mar 18, 2015)

I measured, I should be around .020" squish without a base gasket. Just squaring up my ports and cleaning up casting crud in the transfers cant hurt me can it? Please let me know if this is OT, I dont want to muck up the direction of this thread. How much would you charge me to machine my base and squishband if I sent my jug in?


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## SS396driver (Mar 20, 2015)

This saw is sitting on my kitchen table now...


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## MillerModSaws (Mar 20, 2015)

SS396driver said:


> This saw is sitting on my kitchen table now...


Awaiting this pretty thing!


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## blsnelling (Mar 20, 2015)

Fly By Night said:


> How much would you charge me to machine my base and squishband if I sent my jug in?


Porting is required if you do that. Port timing changes too much.


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## GCJenks204 (Feb 5, 2016)

Carl, Thanks for this great thread. I don't need a saw that big but CAD has me thinking...


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