# Progressive Modding of a Dolmar 7900



## blsnelling (Aug 20, 2009)

At the risk of failing publically, I'm going to show the progression of events as I mod this Dolmar 7900 with the HD filter setup. I'll tell you right up front, this is the first 7900 I've modded. The 7900BB prototype I demod was left stock except for a muffler mod. If I screw it up, I'll put a new topend on it and be done with it. However, I've yet to see a saw that didn't respond to a little port and muffler work. With that disclaimer out of the way, here we go.

To start off, I heat cycled the saw a couple times, allowing it to cool off after only getting it good and warm. No cutting or WOT. I then cut 2-3 cookies and let it cool again. I've now trimmed the H limiter cap and tuned it in an Ash log. 

This first video is a bone stock saw with the exception of trimming the limiter stops.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/seknqVRtK2c&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/seknqVRtK2c&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## FELLNORTH (Aug 20, 2009)

I'D REP YA BUT IT WONT LET ME....
THANX FOR VIDS... ALWAYS A PLEASURE.
I LOOK FORWARD TO SEE THE PROGRESSION


----------



## blsnelling (Aug 20, 2009)

I'll mod the muffler next and get some more vids. Then I'll finally go in and do the port work for the final mods.


----------



## fredmc (Aug 20, 2009)

Are you gonna share the port mapping and such? I've yet to touch mine other than the matching, MM and an .019 squish I did. In fact my 7901 fells trees better than any other saw I've used at that weight modded or not. It bores well, limbs, bucks and noodles like a raped chimp on meth.


----------



## TRI955 (Aug 20, 2009)

opcorn:


----------



## blsnelling (Aug 20, 2009)

fredmc said:


> Are you gonna share the port mapping and such?



I'll share any info or anything I learn along the way.


----------



## fredmc (Aug 20, 2009)

blsnelling said:


> I'll share any info or anything I learn along the way.



Far out!


----------



## blsnelling (Aug 20, 2009)

fredmc said:


> Far out!



No reason to change now. No secrets here.


----------



## nmurph (Aug 20, 2009)

are you going with the unlimited coil and re-keying the flywheel???


----------



## blsnelling (Aug 20, 2009)

nmurph said:


> are you going with the unlimited coil and re-keying the flywheel???



No. As much as I'd love to not have a limited coil, I'm not a fan of a keyless flywheel. Especially on a customers worksaw.


----------



## roncoinc (Aug 20, 2009)

> blsnelling Progressive Modding of a Dolmar 7900
> 
> --------------------------------------------------------------------------------
> At the risk of failing publically,




After what i have read the last year,,have you ever failed at ALL ??

now tell me how to port my ryobi !!


----------



## Andyshine77 (Aug 20, 2009)

My ported 7900 has three 1/2" holes in the front of the muffler. Don't remove the baffle cage in the muffler, you can open it up a little, but it's not really necessary. Don't go bigger than whatever the volume of 3 1/2' holes comes out to, if you go bigger you'll lose power.


----------



## angelo c (Aug 20, 2009)

Andyshine77 said:


> My ported 7900 has three 1/2" holes in the front of the muffler. Don't remove the baffle cage in the muffler, you can open it up a little, but it's not really necessary. Don't go bigger than whatever the volume of 3 1/2' holes comes out to, if you go bigger you'll lose power.



Andy, 
How did you go about opening up the muff ? any Pics ?
A


----------



## MCW (Aug 20, 2009)

I watched a really good girly video on the internet last night (OK, maybe not) but have a feeling that the progressive mod videos on this saw will be far more entertaining. That looks like pretty hard wood too?
Brad, I hope you don't have to wear earplugs and earmuffs after any muffler mods?


----------



## Andyshine77 (Aug 20, 2009)

angelo c said:


> Andy,
> How did you go about opening up the muff ? any Pics ?
> A



I didn't open up the muffler myself, the saws builder did. It's simple but effective, some people like it some don't. 

Sorry about the image quality.


----------



## Tree Sling'r (Aug 20, 2009)

Strictly porting Brad, or are you getting some machine work done?


----------



## angelo c (Aug 20, 2009)

Thanks Andy, 
any spark arrestor or is it "free balling"...


----------



## blsnelling (Aug 20, 2009)

Tree Sling'r said:


> Strictly porting Brad, or are you getting some machine work done?



No machine work planned.


----------



## blsnelling (Aug 20, 2009)

Andyshine77 said:


> My ported 7900 has three 1/2" holes in the front of the muffler. Don't remove the baffle cage in the muffler, you can open it up a little, but it's not really necessary. Don't go bigger than whatever the volume of 3 1/2' holes comes out to, if you go bigger you'll lose power.



Now you tell me, lol. Looks like I proved your point. I gutted the internal cage. I then opened up the factory exit and replaced the screen. I also added a second port and used a Husky deflector. It could be that it's not tuned perfectly. Back to the drawing board. 

















It sure sounds good

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/IU8oDgS31js&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/IU8oDgS31js&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## MCW (Aug 20, 2009)

Excellent job mate, nice work.
Looks like there may have been a bit of supercharging going on too with the wind in the background


----------



## Work Saw Collector (Aug 20, 2009)

Threads like this are one of the reasons I hang around so much. Cool post Brad.


----------



## Andyshine77 (Aug 20, 2009)

It sounds good and looks really professional. 

I think the muffler cage on the 7900 is tuned, and gives you a bit of scavenging. If you look at the cage you can see it flows a ton, and is not really restrictive at all.


----------



## spacemule (Aug 20, 2009)

And this is why you have to be leery of places like this. Three people congratulating Brad when he just posted that it didn't help. He did make it louder and trailer house worthy though. ;-)


----------



## Work Saw Collector (Aug 20, 2009)

spacemule said:


> And this is why you have to be leery of places like this. Three people congratulating Brad when he just posted that it didn't help. He did make it louder and trailer house worthy though. ;-)



Thats not the point.


----------



## TRI955 (Aug 20, 2009)

spacemule said:


> And this is why you have to be leery of places like this. Three people congratulating Brad when he just posted that it didn't help. He did make it louder and trailer house worthy though. ;-)



Space, is your glass _always_ half empty???


----------



## Andyshine77 (Aug 20, 2009)

The reason people are congratulating him, is because he's being completely open, and is sharing his results, good or bad on a public forum.


----------



## sprung22 (Aug 20, 2009)

I think a lot like jashar's post a while back when he modded a 7900 the gain's on this saw just do not seem worth the time and effort to me when you can have the same work done to similar cc size saws and see dramatic gains.But I do like the vid's Brad and your enthusiasm to get every little bit out of a saw.Keep up the good work.


----------



## fredmc (Aug 20, 2009)

I cut the front off the cage in mine and added a 9/16 tube. It made a big difference with mine.


----------



## super3 (Aug 20, 2009)

spacemule said:


> And this is why you have to be leery of places like this. Three people congratulating Brad when he just posted that it didn't help. He did make it louder and trailer house worthy though. ;-)




Those that want to mod one will now know what doesn't work. How do you think all this stuff gets figured out? Lots of failures to get to the point where you know what works.


----------



## angelo c (Aug 20, 2009)

If a tree falls in the Forrest and there is no attorney there to hear it, can anyone really capitalize or earn from its negligent actions....

If you ignore him he will go away....

( just ask Kevin Costner...have you seen has last few movies ?)


----------



## Andyshine77 (Aug 20, 2009)

fredmc said:


> I cut the front off the cage in mine and added a 9/16 tube. It made a big difference with mine.



That's a good idea, maybe the pipe helps. I know of a few good running stock 7900, that have muffler mods with pipes.


----------



## sprung22 (Aug 20, 2009)

angelo c said:


> If a tree falls in the Forrest and there is no attorney there to hear it, can anyone really capitalize or earn from its negligent actions....
> 
> If you ignore him he will go away....
> 
> ( just ask Kevin Costner...have you seen has last few movies ?)



So which one's the Dolmar 7900-->Got it Kevin Costner


----------



## brncreeper (Aug 20, 2009)

How's the compression and squish?
To me, the new muffler side port looks much better than a frontal dill job.


----------



## B_Turner (Aug 20, 2009)

I love the progressive vid thing. The truth is in the cutting, not the volume.

Thanks and keep it coming , Brad.


----------



## spacemule (Aug 20, 2009)

super3 said:


> How do you think all this stuff gets figured out?



Reading the responses, it's obvious that it doesn't.


----------



## Andyshine77 (Aug 20, 2009)

brncreeper said:


> How's the compression and squish?
> To me, the new muffler side port looks much better than a frontal dill job.



I completely agree.


----------



## AUSSIE1 (Aug 20, 2009)

opcorn: on all accounts.


----------



## angelo c (Aug 20, 2009)

sprung22 said:


> So which one's the Dolmar 7900-->Got it Kevin Costner



Naw i was referring to Space...he's an aspriring attorney....if you don't argue with him....

the 7900 is way too good of a machine to be ignored...Brads just trying to tweak a little more out of one...


----------



## blsnelling (Aug 20, 2009)

I blocked of the factory exit with a piece of sheet metal the same shape as the screen. I'm guessing the new port to be about equal to yours Andy. The times only changed a few tenths. However, only one stock cut was faster than all four of these in this next video. IMHO, the bottom line is, there's no need to mod the muffler on a stock 7900. I personally like the way it sounds better, but the cuts times didn't change much at all.

I'm going to go ahead and pop the P&C off and get work inside. I'll play with the exhaust tuning some more once it's ported.

BTW, I've now got one tank of fuel through it.

I have not measured compression or squish. I will before I tear it down.


<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/95sNuayCTIw&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/95sNuayCTIw&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## blsnelling (Aug 20, 2009)

I've also got to quit playing with the muffler because I'm working up to the larger end of the log. You'd think I'd learn to start on the big end


----------



## B_Turner (Aug 20, 2009)

Also the saw is breaking in. About half the saws I've bought gained alot the first 3 to 15 tanks depending on the saw. My 346 was a turd the first tank.

And one of my 3120s got ALOT stronger after a few tanks. Night and day and I changed nothing.


----------



## 4mocajuns (Aug 20, 2009)

<a href="http://www.sweetim.com/s.asp?im=gen&lpver=3&ref=11" target="_blank"><img src="http://cdn.content.sweetim.com/sim/cpie/emoticons/000202C4.gif" border="0" title="Click to get more." ></a>


----------



## blsnelling (Aug 20, 2009)

4mocajuns said:


> <a href="http://www.sweetim.com/s.asp?im=gen&lpver=3&ref=11" target="_blank"><img src="http://cdn.content.sweetim.com/sim/cpie/emoticons/000202C4.gif" border="0" title="Click to get more." ></a>



I'm grinding right now


----------



## 4mocajuns (Aug 20, 2009)

blsnelling said:


> I'm grinding right now



Brown CHicken Brown Cow.......




Oh wait you mean grinding on the cylinder!<a href="http://www.sweetim.com/s.asp?im=gen&lpver=3&ref=11" target="_blank"><img src="http://cdn.content.sweetim.com/sim/cpie/emoticons/000203F2.gif" border="0" title="Click to get more." ></a>


----------



## blsnelling (Aug 20, 2009)

She's done and back together. Unfortunately, it'll be tomorrow afternoon before I get to cut with it.


----------



## blsnelling (Aug 20, 2009)

brncreeper said:


> How's the compression and squish?
> To me, the new muffler side port looks much better than a frontal dill job.



Squish is .022. Compression is 153. I left the squish where it was. This a work saw and will likely see some heavy duty use from what MCW has been showing us of his job.

Quite honestly, this 7900 doesn't look much different inside from a 361, 357, or 372. It does have a single ring, so that made port layout simple. Skirt width will not allow 70% port width. I left transfer and exhaust port timing stock. I lowered the intake a couple degrees. I widened both the exhaust and intake, and widened the rear transfers towards the intake. I then port matched the muffler, heat shield, and gasket. We'll see tomorrow if it worked


----------



## brncreeper (Aug 21, 2009)

blsnelling said:


> Squish is .022. Compression is 153. I left the squish where it was. This a work saw and will likely see some heavy duty use from what MCW has been showing us of his job.
> 
> Quite honestly, this 7900 doesn't look much different inside from a 361, 357, or 372. It does have a single ring, so that made port layout simple. Skirt width will not allow 70% port width. I left transfer and exhaust port timing stock. I lowered the intake a couple degrees. I widened both the exhaust and intake, and widened the rear transfers towards the intake. I then port matched the muffler, heat shield, and gasket. We'll see tomorrow if it worked



After seeing MCW work pictures it sounds like a wise move on the compression. Too bad about the skirt. That surprises me on just one ring, it should be a real screamer! Looking forward to the pictures.


----------



## tdi-rick (Aug 21, 2009)

brncreeper said:


> [snip]
> Too bad about the skirt. That surprises me on just one ring, it should be a real screamer! Looking forward to the pictures.



Well known limitation for porting the 7900 using the OE piston. Skirt width is 32mm across the chord, OE port width is 26mm.

Good squish measurement straight up, I wouldn't have played with it either.
Did you measure the port timing before starting ?
How did you approach the lower transfers, bridge between them and how the piston windows feed them ?

Much lightening on the piston, or only casting dags removed ?


----------



## TraditionalTool (Aug 21, 2009)

blsnelling said:


> Now you tell me, lol. Looks like I proved your point. I gutted the internal cage. I then opened up the factory exit and replaced the screen. I also added a second port and used a Husky deflector. It could be that it's not tuned perfectly. Back to the drawing board.


Time wise they were very similar, and the first video when it was stock has one of the fastest runs as the 2nd run, just over 12 seconds.

Curious about the muffler mod, is this the style you would do on the 359?

This looks like it wouldn't require any brazing or welding, just cut out the sides and use a screen. You mention those are Husky vent covers, what type of saw were they off of?

Cheers,
TT


----------



## Zombiechopper (Aug 21, 2009)

TraditionalTool said:


> Time wise they were very similar, and the first video when it was stock has one of the fastest runs as the 2nd run, just over 12 seconds.
> 
> Curious about the muffler mod, is this the style you would do on the 359?
> 
> ...


+1 on the vent info. Is there a part number?


----------



## outdoorlivin247 (Aug 21, 2009)

4mocajuns said:


> Brown CHicken Brown Cow.......
> 
> 
> 
> ...



We were just talking about that the other night...LOL


----------



## tdi-rick (Aug 21, 2009)

Husky deflector # *503 07 83-01* (off a 281 ??) seems the popular choice.


----------



## MCW (Aug 21, 2009)

blsnelling said:


> This a work saw and will likely see some heavy duty use from what MCW has been showing us of his job.



Best bit is that it will be run in when I get it (not that I've ever taken any notice of "running in") so it'll be straight to work. I'll get a few vids and photos up ASAP when it arrives to show you it's new home and me giving it a hammering 
I hope it's not too good though as I don't want to retire my old 7900 just yet! I do have this compulsive habit type thing going on with chainsaws...


----------



## wendell (Aug 21, 2009)

I asked this on another thread but never got a response (I think I killed the thread ) What is "squish"?


----------



## MCW (Aug 21, 2009)

wendell said:


> I asked this on another thread but never got a response (I think I killed the thread ) What is "squish"?



This is my saw and I'm not even sure! I just do the cutting and saw maintainence. I leave saw mechanics to the experts.
I think it is a term used for determining piston clearance, could be wrong?


----------



## angelo c (Aug 21, 2009)

wendell said:


> I asked this on another thread but never got a response (I think I killed the thread ) What is "squish"?



Wendell, 
Try this link.

http://www.sacoriver.net/~red/squish.html


----------



## tdi-rick (Aug 21, 2009)

wendell said:


> I asked this on another thread but never got a response (I think I killed the thread ) What is "squish"?



Short answer first.

In this instance it's a bit of a misnomer, what we are actually talking about is piston to head clearance, or more precisely, piston to *squish* band clearance.

The squish band is the area of the head nearest the cylinder wall that closely follows the piston crown shape, having minimal clearance between the two. The combustion chamber is then set somewhere in the middle of this band. The chamber can either be centralised or offset, depending on what the design engineer is tying to achieve, but that band around the outside of it is still a squish band, even though it may vary in size.

In simple terms, the narrower that gap, the more efficient your combustion process will be and it dramatically reduces the chances of detonation occurring (very unlikely in a saw anyway) as the end gasses have been 'squished' back into the chamber, not lingering out near the cylinder wall where they may self ignite, a long way from where ignition is supposed to start occurring.
The reason for the gain in efficiency is that you are squeezing the maximum amount of charge (fuel/air mixture) into the combustion chamber where it can be ignited by the plug. 
If the squish clearance is too great, anything up to 10% of your charge will be wasted, igniting far too late to get any real work out of it as it's so far from the plug and chamber proper. 

This squish clearance can also be too little, leading to piston and squish band hitting as things stretch under the extreme forces or even through just a bit of carbon buildup.


----------



## blsnelling (Aug 21, 2009)

tdi-rick said:


> Well known limitation for porting the 7900 using the OE piston. Skirt width is 32mm across the chord, OE port width is 26mm.
> 
> Good squish measurement straight up, I wouldn't have played with it either.
> Did you measure the port timing before starting ?
> ...


Is there a known replacement piston with wider skirts?

I did not measure port timing since I knew I was going to be working with the stock timing.

I did sharpen the divider in the transfer intake.

I do quite a bit of work to the piston. All four holes are tapered and flowed from the inside out. A lot of material is removed.



TraditionalTool said:


> Curious about the muffler mod, is this the style you would do on the 359?
> 
> This looks like it wouldn't require any brazing or welding, just cut out the sides and use a screen.


I use this deflector and spark arrestor screen on many of the mufflers I mod, including the 359/357.



Zombiechopper said:


> +1 on the vent info. Is there a part number?


503589901 EXHAUST OUTLET $8.74 
503405601 SPARK ARRESTOR $4.97


----------



## TraditionalTool (Aug 21, 2009)

blsnelling said:


> I use this deflector and spark arrestor screen on many of the mufflers I mod, including the 359/357.
> 
> 503589901 EXHAUST OUTLET $8.74
> 503405601 SPARK ARRESTOR $4.97


I just punched them into Bailey's but nothing comes up. Maybe this is something that has to be special ordered from them???

It looks clean and I think that would work out well for me,

Cheers,
TT


----------



## fredmc (Aug 21, 2009)

blsnelling said:


> Is there a known replacement piston with wider skirts?



Anybody got an answer for this question? inquiring minds wanna know.


----------



## blsnelling (Aug 21, 2009)

TraditionalTool said:


> I just punched them into Bailey's but nothing comes up. Maybe this is something that has to be special ordered from them???
> 
> It looks clean and I think that would work out well for me,
> 
> ...



Those are Husqvarna PNs.


----------



## KMB (Aug 21, 2009)

TraditionalTool said:


> I just punched them into Bailey's but nothing comes up. Maybe this is something that has to be special ordered from them???
> 
> It looks clean and I think that would work out well for me,
> 
> ...



deflector

screen


----------



## TraditionalTool (Aug 21, 2009)

KMB said:


> deflector
> 
> screen


Thanks,

Not sure why those didn't show up...I guess it wanted the '+' signs between the numbers...

Thanks KMB!


----------



## KMB (Aug 21, 2009)

TraditionalTool said:


> Thanks,
> 
> Not sure why those didn't show up...I guess it wanted the '+' signs between the numbers...
> 
> Thanks KMB!



Your welcome.

I admit I stumbled onto the parts at Bailey's by chance. I had punched in different words and combos such as 'husqvarna muffler deflector' and 'muffler deflector' and 'deflector' and one of them brought up the right part. Then just to see what it would bring up, I punched in the part number as one number with out spaces...nothing. Then tried with the proper spaces and it worked. I'm guessing that punching in other Husky part numbers (or whatever brand Bailey's deal with) (with the correct spacing) might work also.

Kevin


----------



## tdi-rick (Aug 21, 2009)

blsnelling said:


> Is there a known replacement piston with wider skirts?
> 
> [snip]



Not any that are plug and play, at least not that I'm aware of.

I've heard of a 281 piston being used but can't remember what was required re the gudgeon (pin) and whether the rod needed changing too.

Found pics (one of Brad's threads) of the deflectors http://www.arboristsite.com/showthread.php?p=1434853


----------



## blsnelling (Aug 21, 2009)

Good news!!! I didn't slow it down, lol

Keep in mind this log was getting larger as I went. I grabbed and earlier piece out of the pile and it was 1 1/2" smaller. 







Even with that in mind, the saw is about 14% faster than stock. I'm pretty happy with that considering this is a saw that has a reputation of being difficult to mod, and can even be slowed down. Honestly, I don't see why it has that reputation. I did the same stuff to this thing that I do to most all my saws. There was one cut that was substantially faster than the rest of the stock cuts. I'm still 10% faster than that cut was even though that first cut was in smaller wood. Bottom line, I'm happy with it. 

I did a little more testing with the muffler after porting. If anything, it slowed down just a hair by blocking the added port. So I've left both ports fully open, with a spark arrestor screen on both.

All tests were done in about 50 year old Ash. This is some good hard wood to test this saw in. Also, the saw has been wearing an 8-pin sprocket for all testing.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/zAWnR7LGHB4&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/zAWnR7LGHB4&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


Here's the stock video just for reference.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/seknqVRtK2c&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/seknqVRtK2c&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>[/QUOTE]


----------



## MCW (Aug 21, 2009)

Somebody is getting excited. Even more so when he read that all testing was with an 8 pin sprocket. Good work.
Are you going to post any pictures of the internals etc?


----------



## blsnelling (Aug 21, 2009)

MCW said:


> Are you going to post any pictures of the internals etc?


I didn't take any since it's really no different than my other porting threads.


----------



## TraditionalTool (Aug 21, 2009)

blsnelling said:


> Good news!!! I didn't slow it down, lol


Looks a good 1 - 2 seconds faster than stock. So about 15 - 20 percent, AFAICT.

Cheers,
TT


----------



## Andyshine77 (Aug 22, 2009)

MCW you're going to really like this saw. It's a beast of a saw, every bit as strong as my EHP-7900, and it's only going to get stronger. As I expected the HD filter looks fine in person, believe it or not, I like it.


----------



## MCW (Aug 22, 2009)

Andyshine77 said:


> MCW you're going to really like this saw. It's a beast of a saw, every bit as strong as my EHP-7900, and it's only going to get stronger. As I expected the HD filter looks fine in person, believe it or not, I like it.



Good to hear mate. Can't wait for it to arrive. Any hint of Brad secretly trying to buy one himself? I actually don't mind the look of the HD filter despite some unflattering photos early.


----------



## scotclayshooter (Aug 22, 2009)

blsnelling said:


> Squish is .022. Compression is 153. I left the squish where it was. This a work saw and will likely see some heavy duty use from what MCW has been showing us of his job.
> 
> QUOTE]
> 
> ...


----------



## tdi-rick (Aug 22, 2009)

scotclayshooter said:


> Mine was over 190psi and the squish ar 0.026" stock!
> No de-comp on my one It will break your wrist if your not committed to starting it!



I contemplated a standard P&C for about a nano-second.
I'm too girly for that. 

Yes, I do yoga, eat lentils and sip lattés :greenchainsaw:


----------



## MCW (Aug 22, 2009)

tdi-rick said:


> I contemplated a standard P&C for about a nano-second.
> I'm too girly for that.
> Yes, I do yoga, eat lentils and sip lattés :greenchainsaw:



I busted my right wrist about 15 years ago and every time I forget to push the decomp in I am reminded of it. The worst saw I have for tweaking my wrist again is my 5100-S. I can't believe some of the bigger, older saws can even be started without a decomp but where there's a will there's a way I suppose!
I'm with you here Rick, just without the yoga, lattés and lentils


----------



## PetrolHead (Aug 22, 2009)

Fantastic, just fantastic. 
I actually don't mind the look of the HD filter setup, doesnt seem to protrude into the abyss like the Husky setup.

Here's an idea, seeing as though it's coming to SA anyway, divert it my way and I'll check it for freight damage etc. No need to thank me, that's just the sort of bloke I am.


----------



## MCW (Aug 22, 2009)

PetrolHead said:


> Fantastic, just fantastic.
> I actually don't mind the look of the HD filter setup, doesnt seem to protrude into the abyss like the Husky setup.
> Here's an idea, seeing as though it's coming to SA anyway, divert it my way and I'll check it for freight damage etc. No need for a thank me, that's just the sort of bloke I am.



I may never see it again though. Feel free to come to the Riverland and knock over a few Casuarinas if you want. I may even let you touch it and sniff it 
Tried out the Windsor yet?


----------



## tdi-rick (Aug 22, 2009)

MCW said:


> [snip]
> I may even let you touch it and sniff it



What exactly _are_ we talking about here fella's ?
and if it is the saw, I wouldn't after seeing what Brad did to it :jawdrop:


----------



## PetrolHead (Aug 22, 2009)

MCW said:


> I may never see it again though. Feel free to come to the Riverland and knock over a few Casuarinas if you want. I may even let you touch it and sniff it
> Tried out the Windsor yet?



Mate, I feel like a peasant with a kings invite. You enjoy that saw Matt, "edit here" (did'nt sound right after Rick's comment!)


----------



## MCW (Aug 22, 2009)

tdi-rick said:


> I wouldn't after seeing what Brad did to it :jawdrop:



Well I'd hope he's washed it?



PetrolHead said:


> Mate, I feel like a peasant with a kings invite. You enjoy that saw Matt, now if youll excuse me, I have some drool to mop up from my chin.



No Kings here mate and I'm sure I'll enjoy the saw. Anyone that ever wants to come chainsawing with me is more than welcome.


----------



## blsnelling (Aug 22, 2009)

scotclayshooter said:


> Mine was over 190psi and the squish ar 0.026" stock!



They must have made some changes then. Last night Andyshine tested his and it was 155 and this one was 152 on the same guage.


BTW, I caught a woman with a bad attitude at the Post Office this morning. She wouldn't ship it. I told her all fuel and oil were drained. She didn't care and was rather rude about it. Fine. I came home and printed my own shipping labels like I normally do. I'll just need to pick up the plastic envelope that the forms are required to be put in. My mailman has delivered many a chainsaw here and won't have one problem with it. It does amaze me though when someone ships a saw with fueal and/or oil in it


----------



## mowoodchopper (Aug 22, 2009)

blsnelling said:


> They must have made some changes then. Last night Andyshine tested his and it was 155 and this one was 152 on the same guage.
> 
> 
> My 6400 is the same also.


----------



## blsnelling (Aug 22, 2009)

scotclayshooter said:


> My 6400 is the same also.



Same way as in 155 or 190?


----------



## Andyshine77 (Aug 22, 2009)

I'm actually a bit concerned about the reading on my ported 7900, the last time I checked the compression it was well over 180. It may have been the fact I ran the saw an hour before I tested it, or it a gauge issue.:dunno: I'll test my stock when I get my gauge back.


----------



## mowoodchopper (Aug 22, 2009)

blsnelling said:


> Same way as in 155 or 190?



150-160 brad and looks like new inside.


----------



## rahtreelimbs (Aug 22, 2009)

This is another way to go on a 7900 muffler. Functional but doesn't look as good as Brads!

On the first pic you 'll notice that I opened up the factory port too!


IMG]http://www.arboristsite.com/attachment_29586.php[/IMG]

/http://www.arboristsite.com/attachment_29590.php


----------



## scotclayshooter (Aug 22, 2009)

blsnelling said:


> Same way as in 155 or 190?



Err im not sure what you quoted of mine but ive never had a 6400??????

Im sure my guage is near right and yes it has a shrader valve

At 155 i would say it aint run in!

My 7900 will just stop the rope when i try to start it and pull the handle out of my hand, If i had the know how i would fit a de-comp!


----------



## mowoodchopper (Aug 22, 2009)

Something is messed up with the quote system, it did it to me earlier. I quoted Brad and something else came up. My 6400 is broken in and is about 150-160 as I said .


----------



## mowoodchopper (Aug 22, 2009)

rahtreelimbs said:


> This is another way to go on a 7900 muffler. Functional but doesn't look as good as Brads!
> 
> 
> 
> ...



Looks good to me!!!!


----------



## Work Saw Collector (Aug 22, 2009)

mowoodchopper said:


> Looks good to me!!!!



Me too.


----------



## rahtreelimbs (Aug 22, 2009)

mowoodchopper said:


> Looks good to me!!!!





supercabs78 said:


> Me too.




The nice thing with this method is that you can open up the cage with the hole in the front!


----------



## scotclayshooter (Aug 22, 2009)

rahtreelimbs said:


> The nice thing with this method is that you can open up the cage with the hole in the front!








I did mine the hard way!


----------



## mowoodchopper (Aug 22, 2009)

rahtreelimbs said:


> The nice thing with this method is that you can open up the cage with the hole in the front!



How does she sound? I like it when they have a nice pop to them at idle.


----------



## rahtreelimbs (Aug 22, 2009)

mowoodchopper said:


> How does she sound? I like it when they have a nice pop to them at idle.





Sounds good.........mine is modded but sounds good stock.


A few years, most you guys weren't here, a whole different crowd was here and we did the GTG thing a lot. I attended 5 in all. Anyway I decided to try my hand at warming over a 7900. I have since sold the saw but it ran nice, I eliminated the base gasket giving a squish of .022." I also cleaned up all the casting flash and worked the piston a little plus a muffler mod!


----------



## mowoodchopper (Aug 22, 2009)

mowoodchopper said:


> 150-160 brad and looks like new inside.



I just went and checked mine for you again brad, its never been tore down but looks exc through the port, has ran klotz at 40-1 all its life and has been used 1 season and part of another, IMO its as strong as it was new and is at 152 right now.


----------



## 4mocajuns (Aug 22, 2009)

Here is how I modded my muffler


----------



## mowoodchopper (Aug 22, 2009)

4mocajuns said:


> Here is how I modded my muffler



Where is Iberia?


----------



## rahtreelimbs (Aug 22, 2009)

4mocajuns said:


> Here is how I modded my muffler




That isn't bad idea..........did you de-burr the inside of all the holes???


----------



## 4mocajuns (Aug 22, 2009)

mowoodchopper said:


> Where is Iberia?



45 min south of Jefferson City and 25 min north of Ft Leonard Wood


----------



## 4mocajuns (Aug 22, 2009)

rahtreelimbs said:


> That isn't bad idea..........did you de-burr the inside of all the holes???



I drilled it with the saw running (chain brake on) an used a dental pick to check for large burrs. But there are probably some small ones still hanging around.


----------



## rms61moparman (Aug 22, 2009)

blsnelling said:


> They must have made some changes then. Last night Andyshine tested his and it was 155 and this one was 152 on the same guage.
> (





Just went out and tested mine, just shy of 170.

Of course my gauge is about as junky as my saws, so I will have to test again with the one youall used sometime.

Pulled a flat 120 with the compression release pushed in. The same as my 3400! LOL


Mike


----------



## TraditionalTool (Aug 22, 2009)

rahtreelimbs said:


> This is another way to go on a 7900 muffler. Functional but doesn't look as good as Brads!


Yeah, Brad's muffler mod is pretty sexy in comparison. You have him beat cost wise!


----------



## blsnelling (Aug 22, 2009)

TraditionalTool said:


> Yeah, Brad's muffler mod is pretty sexy in comparison. You have him beat cost wise!



This saw didn't cost me a dime. Uhhh, but it's not mine, lol.


----------



## 4mocajuns (Aug 22, 2009)

Mine with about 5 tanks thru it is just north of 150 cold


----------



## TraditionalTool (Aug 22, 2009)

blsnelling said:


> This saw didn't cost me a dime. Uhhh, but it's not mine, lol.


Nothing wrong with that, give you some free toys to play with, huh?

I should have noted on rahtreelimbs mod, his weld was XLNT, if I could weld like that I might try something like he did, but I think I'm better off going the route you did with the 288 deflectors/spark arrester.


----------



## angelo c (Aug 22, 2009)

Just north of 150 for me too. I was wondering if the BB kit was designed to deliver that as a goal for a happy medium of power/reliability.

All the kits(3) I got from Bailey's have come in at the same range.


----------



## blsnelling (Aug 22, 2009)

TraditionalTool said:


> Nothing wrong with that, give you some free toys to play with, huh?
> 
> I should have noted on rahtreelimbs mod, his weld was XLNT, if I could weld like that I might try something like he did, but I think I'm better off going the route you did with the 288 deflectors/spark arrester.



No. This saw was bought for MCW to be ported and then shipped to AU.


----------



## TraditionalTool (Aug 22, 2009)

blsnelling said:


> No. This saw was bought for MCW to be ported and then shipped to AU.


Yeah, that's what I said...gives you some free toys to play with!


----------



## blsnelling (Aug 22, 2009)

TraditionalTool said:


> Yeah, that's what I said...gives you some free toys to play with!



Ahhh. Gotcha


----------



## spacemule (Aug 22, 2009)

rahtreelimbs said:


> This is another way to go on a 7900 muffler. Functional but doesn't look as good as Brads!
> 
> On the first pic you 'll notice that I opened up the factory port too!
> 
> ...



Looks like a great way to set the bark on fire.


----------



## fredmc (Aug 22, 2009)

spacemule said:


> Looks like a great way to set the bark on fire.



A saw ain't a saw till it breathes fire and burns the bark!


----------



## rahtreelimbs (Aug 22, 2009)

spacemule said:


> Looks like a great way to set the bark on fire.




Who cares!!!


----------



## spacemule (Aug 22, 2009)

Dude, you're the kind of guy who couldn't poor piss out of a boot with instructions on the heel.


----------



## rms61moparman (Aug 22, 2009)

That bark is gonna be on fire soon anyway!!!


----------



## yodayoda (Aug 22, 2009)

spacemule said:


> Dude, you're the kind of guy who couldn't poor piss out of a boot with instructions on the heel.



LOL, never heard that one before

Someone piss in your wheaties this morning space?


----------



## PetrolHead (Aug 23, 2009)

spacemule said:


> Dude, you're the kind of guy who couldn't poor piss out of a boot with instructions on the heel.



I knew a bloke once that couldn't find his own arse with a seeing eye dog!
But I don't want to de rail the thread.

Hope the saw goes through ok.


----------



## rahtreelimbs (Aug 23, 2009)

spacemule said:


> Dude, you're the kind of guy who couldn't poor piss out of a boot with instructions on the heel.





Kinda sucks that I read that to take a leak!!!


Luckily too that instructions are written on the toilet paper!!!


----------



## gink595 (Aug 23, 2009)

After seeing what everyone elses compression readings were, I went and tested my 7900, it blew 185. That is about 10 lbs higher than the last time I checked a while ago, my guess it is broke in now and it is completely stock even the muffler


----------



## B_Turner (Aug 23, 2009)

gink595 said:


> After seeing what everyone elses compression readings were, I went and tested my 7900, it blew 185. That is about 10 lbs higher than the last time I checked a while ago, my guess it is broke in now and it is completely stock even the muffler



Seems a little high. I might check my mine sometime for grins. I was guessing more like maybe 160-5.

I still think modding saws from new using timings to judge performance gains is problematic. Certain saws pick up 10 percent just from breaking in a tank or two.

Although both my 7900s pretty much ran full steam right out of the box. But my 346 was a real turd at first and it woke up quite a bit.


----------



## gink595 (Aug 23, 2009)

B_Turner said:


> Seems a little high. I might check my mine sometime for grins. I was guessing more like maybe 160-5.
> 
> I still think modding saws from new using timings to judge performance gains is problematic. Certain saws pick up 10 percent just from breaking in a tank or two.
> 
> Although both my 7900s pretty much ran full steam right out of the box. But my 346 was a real turd at first and it woke up quite a bit.



Mine ran really strong right out of the box, I've never been displeased with it's performance, I'm sure no two saws will have the same compression readings, to many machine tolerances variances in production.


----------



## B_Turner (Aug 23, 2009)

gink595 said:


> Mine ran really strong right out of the box, I've never been displeased with it's performance, I'm sure no two saws will have the same compression readings, to many machine tolerances variances in production.



I love both my 7900s, my favorite saws to run of all my saws.

But one of them is just a little stronger and smoother than the other. Just a touch but discernable.

And of the three 3120s I've owned (from new) one was much stronger than any other 3120 I've run. Wish I knew why, so I could have it done to my current 3120s. Even with a 50 inch bar I pretty much could not stop the chain levering with all my might on that saw. Got rid of it because of the low limiter before I knew about swapping out the coil and flywheel which I did later on two.


----------



## Andyshine77 (Aug 23, 2009)

Some saws will run stronger than others out of the box. My 346 runs really really strong, and it has from day one. I run my 7900's more than my other saws, it's definitely my favorite work saw. The compression readings have a lot of variables as well, you'll probably never get the same reading from one day to the next.


----------



## MCW (Sep 5, 2009)

Well my new 7900 from Brad arrived Wednesday 
I had a decent sized Silky Oak log out the back of my house that I'd given it a run on after work with a 32" bar buried and LGX non skip and although not overly hard wood it was instantly apparent that this saw kicks my stock 7900's arse.
Today I gave it a run in the real world and to say I'm impressed is an understatement. Cutting cookies on Youtube for fun is one thing (I enjoy watching/doing them), but getting this saw out working is a whole different ballgame. The 14% odd speed improvement that Brad had noted seems more like 25% although today was the first time I have run full chisel on this property. It held up well too so will be using it again 
This saw pulls full chisel skip way faster than my stock saw pulls semi chisel skip - *WAY* faster...
With Carlton A3LM skip full chisel it cut that fast on a 32" bar and 7 pin sprocket (although trees were only up to maybe 28"?) that I actually cut too far into the hingewood on a few and was lucky not to lose control of the tree!
Fuel economy was also quite good which was something that had been a small concern but in reality the difference wasn't major although it was noticable. This was made up for with cutting speed.
The muffler mod also isn't overly deafening but when echoing off a tree trunk close to your head I have realised today that my already marginal earmuff/helmet setup aren't good enough with this saw. That's a damn fine excuse to get a decent Peltor setup like I've always wanted 
I was also a bit worried that the saw may lose torque which some people had mentioned - absolute garbage on this saw and a testament to Brad's work.
The saw started, ran, and idled like a factory saw (all while sounding tougher!) and Brad's tune was spot on.

I'd like to thank Brad for -

1) Doing the work.
2) Doing GOOD work.
3) Being open on the forum about what worked and what didn't despite Spacemule's best efforts to derail it 
4) For continuously updating me on what was going on (my PM box was overflowing - does this man ever sleep?).
5) Being honest throughout the whole deal even when he found postage to Australia cost less than he'd quoted.
6) For modding his first (and it won't be his last!) 7900.
7) For now secretly trying to buy a 7900 without anybody knowing. Come on Brad, you know it's true  You have been asking an awful lot of Dolmar questions since playing with my saw!!!

Good service is hard to find and I am yet to have one bad deal from the US despite being shafted on many business/internet transactions in my own country.

Brad is a credit to arboristsite and if anyone wants a 7900 modded I can recommend where to send it. I know there are other guys that do good mod work too but as this is the only modded saw I own I can only comment on Brad's work. If Brad lived next door I'd be broke and there wouldn't be a tree standing for miles. I'd also have the fastest Echo 290EVL on the planet.

The HD filter setup is also very very impressive. In the flesh it also looks pretty good, it does grow on you for sure. The fit of it is also second to none.
After today's work the filter hardly looked used. A stock filter would have needed a good clean in the same amount of time. This filter setup has placed Dolmar right at the pointy end for pro level saws and anybody now using filters as an excuse to drag down Dolmar's 6400-7900 need a good old fashioned uppercut  Only kidding but you get what I mean. If this was factory fitted it would be even better.

All Dolmar now have to do is release a similar setup for their 5100-S and they'll be right on the money across their pro range of saws.

Another thing which could be improved on the 7900's too that I've noticed in certain species of dry timber. Chips can go straight off the chain into the muffler bolt holes and come out glowing ready to start a fire. I've had to stamp a few spot fires out in dry chips around my woodpile. I've noticed this for a while but had wrongly assumed it was sparks off the chain from hitting dirt etc even though the size of them and the way they floated around didn't add up. OK in nice green forests but concerning in dry areas like mine.
I plan on stuffing the holes with steel wool.

Thanks again Brad and will get real world working vids up ASAP, hopefully next to my stocker.


----------



## Work Saw Collector (Sep 5, 2009)

rep for nice post.


----------



## AUSSIE1 (Sep 5, 2009)

Congrats on the new saw Matt.
Modded saws are at least two things.
A blast and addictive.


----------



## blsnelling (Sep 5, 2009)

Thanks for the review and kind words Matt. I'm more than tickled with your response about the performance of the saw over stock. I love debunking the myth that these don't take to mods. Kind of like 'Slingr has done with the 441. I'll admit, I was a little nervous posting the mod thread when I had no idea what the outcome would be. But that's me. I enjoy sharing with you guys.

I just got to thinking about your comments on feeling like more than 14% gains. I suppose that could be. You're cutting way bigger wood than I was. I know Andyshine77 says the same thing about his ported 7900. So maybe the gains are greater, the longer the bar.

I'm anxiously awaiting on the vids!


----------



## B_Turner (Sep 5, 2009)

blsnelling said:


> Thanks for the review and kind words Matt. I'm more than tickled with your response about the performance of the saw over stock. I love debunking the myth that these don't take to mods. Kind of like 'Slingr has done with the 441. I'll admit, I was a little nervous posting the mod thread when I had no idea what the outcome would be. But that's me. I enjoy sharing with you guys.
> 
> I just got to thinking about your comments on feeling like more than 14% gains. I suppose that could be. You're cutting way bigger wood than I was. I know Andyshine77 says the same thing about his ported 7900. So maybe the gains are greater, the longer the bar.
> 
> I'm anxiously awaiting on the vids!



I'm repeating, but for me I don't want the extra volume.

I think it would be very interesting to do the porting, etc and time it with a stock muffler. I know the gains would not be as much, but seems like gains could be had without extra volume. 

Consider the Univent, for example. Didn't it have a stock 372 muffler?


----------



## blsnelling (Sep 5, 2009)

B_Turner said:


> I'm repeating, but for me I don't want the extra volume.
> 
> I think it would be very interesting to do the porting, etc and time it with a stock muffler. I know the gains would not be as much, but seems like gains could be had without extra volume.
> 
> Consider the Univent, for example. Didn't it have a stock 372 muffler?



Most saws I would say you'd kill the performance. However, we saw how modding the muffler when the saw was stock did nothing for it. A ported 7900 might just run pretty good with a stock muffler. Definately worth trying!


----------



## B_Turner (Sep 5, 2009)

MCW said:


> I plan on stuffing the holes with steel wool.



Do you mean steel wool or rock wool?


----------



## MCW (Sep 5, 2009)

B_Turner said:


> Do you mean steel wool or rock wool?



I have seen some really fne stainless steel wool that I was thinking of using. I'm on my way up to the property in a minute and will drop in to the local supermarket to get a few nibbles so will grab some of this steel wool then. Strong Northerly blowing at the moment which is perfect.
Oh, and a McDonald's breakfast on the way 

Brad, have you ordered *YOUR* 7900 yet? 

The kind words were deserved too.


----------



## Andyshine77 (Sep 5, 2009)

Matt, I'm glad you like the saw, It pulled really well in the wood. The new HD filter is indeed top notch. 

Happy cutting. Andy.


----------



## Jtheo (Sep 5, 2009)

Thanks a bunch for the post and all the information, Brad.:yourock:


----------



## Jtheo (Sep 5, 2009)

blsnelling said:


> Most saws I would say you'd kill the performance. However, we saw how modding the muffler when the saw was stock did nothing for it. A ported 7900 might just run pretty good with a stock muffler. Definately worth trying!



This is a great post.Tried to rep you but the computer said no.


----------



## MCW (Sep 6, 2009)

And some vids from today. Doesn't give a brilliant idea of the saw's potential but sounds good and eats the wood 
The comparo between my stock 7900 and Brad's modded one isn't exactly fair. My old 7900 was wearing new Windsor 63A Semi Chisel non skip and my new 7900 was wearing well worn Carlton A3LM skip. You've still got to respect the standard 7900 though 
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/qVvImeR2k_0&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/qVvImeR2k_0&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/5LC2LKHg3g0&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/5LC2LKHg3g0&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/epoSzLCWAJU&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/epoSzLCWAJU&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/mgUJSnGbNKM&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/mgUJSnGbNKM&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/dRCqMAtfdTE&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/dRCqMAtfdTE&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## MCW (Sep 6, 2009)

And some photos of the HD filter kit in action. At this stage it had seen about 300 trees without cleaning. I would be already considering swapping out my 2nd standard filter at this stage.

Pre filter...







Main filter pre cleaning (wood dust on top came from pulling pre filter off so above photo taken at same time)...






Main filter after simply tapping on hard object. The loose stuff fell off easily...






Being pale coloured wood with a black intake tract there was absolutely no evidence of anything getting through. The real test would be something like dead Redgum and I'll post back when I get stuck into some of that next.


----------



## blsnelling (Sep 6, 2009)

Thanks for posting the videos. Your tuning sounds spot on for the way you use your saws. They're perhaps a hair on the rich side, exactly where I'd want them for a work saw. I regularly hear it burble when you let off the load. I like that since you know it's not lean, but cleans out and cuts very nicely under load.

That's excellent real world reporting on the HD filter setup.  I'm anxious to see similiar pics after some time in Redgum.

So tell use how you really feel about the ported saw. Is it worth modding for a production work saw? Or is the stock 7900 so strong stock you'll just run them stock in the future? It would be nice to see them running the same chain in the same wood for a good comparison.


----------



## Adirondack (Sep 6, 2009)

I notice the screen on the new HD pre filter "appears" to have larger holes than the mesh on the old filter housing. Maybe it is the same size plastic screen mesh but looks different in these pictures. The only reason I even looked at the screen hole size was because I noticed the particles look larger that collected around the filter. Is there a difference?


----------



## MCW (Sep 6, 2009)

blsnelling said:


> Thanks for posting the videos. Your tuning sounds spot on for the way you use your saws. They're perhaps a hair on the rich side, exactly where I'd want them for a work saw. I regularly hear it burble when you let off the load. I like that since you know it's not lean, but cleans out and cuts very nicely under load.
> 
> That's excellent real world reporting on the HD filter setup. I'm anxious to see similiar pics after some time in Redgum.
> 
> So tell use how you really feel about the ported saw. Is it worth modding for a production work saw? Or is the stock 7900 so strong stock you'll just run them stock in the future? It would be nice to see them running the same chain in the same wood for a good comparison.



Tune spot on and saw running a treat Brad. It has gotten stronger in the 12 odd tanks I've put through it since it arrived.
From my point of view in my cutting condtions the modifications are definately worthwhile. What you've done to the saw has basically put to rest my desire/need for a saw in the 90cc class such as a 395XP/660. The new 7900 fills the gap nicely between my stock 7900 and 3120XP.
This thing pulls a 32" bar and 3/8" chain quite easily and even on trees up to 50" I'd probably still just use the new 7900 with 32" bar instead of my 3120XP. I'll probably use this solely on monster trees and on my mill from now on.
In saying that though I used my 3120XP and 32" .404" last weekend on a few larger trees and it is still an impressive beast, although very tiring 



Adirondack said:


> I notice the screen on the new HD pre filter "appears" to have larger holes than the mesh on the old filter housing. Maybe it is the same size plastic screen mesh but looks different in these pictures. The only reason I even looked at the screen hole size was because I noticed the particles look larger that collected around the filter. Is there a difference?



My old 7900 didn't have the newer style housing but from what I've seen on this site the new HD setup does have larger mesh holes than the current newer housing.


----------



## AUSSIE1 (Sep 6, 2009)

MCW said:


> From my point of view in my cutting condtions the modifications are definately worthwhile. What you've done to the saw has basically put to rest my desire/need for a saw in the 90cc class such as a 395XP/660. The new 7900 fills the gap nicely between my stock 7900 and 3120XP.
> This thing pulls a 32" bar and 3/8" chain quite easily and even on trees up to 50" I'd probably still just use the new 7900 with 32" bar instead of my 3120XP.



A lot of people don't understand some of the reasoning behind modding saws.
This is one reason. 
Easier to man handle all day.

Wonder how this saw would feel against a modded 460 for instance?


----------



## MCW (Sep 6, 2009)

AUSSIE1 said:


> A lot of people don't understand some of the reasoning behind modding saws.
> This is one reason.
> Easier to man handle all day.
> 
> Wonder how this saw would feel against a modded 460 for instance?



Exactly right, not to mention I saved a good AUD$600-700 dollars on buying a 395XP/660!
I am not familiar with 460's at all so can't comment on comparisons


----------



## litefoot (Sep 6, 2009)

blsnelling said:


> Squish is .022. Compression is 153. I left the squish where it was. This a work saw and will likely see some heavy duty use from what MCW has been showing us of his job.
> 
> Quite honestly, this 7900 doesn't look much different inside from a 361, 357, or 372. It does have a single ring, so that made port layout simple. Skirt width will not allow 70% port width. I left transfer and exhaust port timing stock. I lowered the intake a couple degrees. I widened both the exhaust and intake, and widened the rear transfers towards the intake. I then port matched the muffler, heat shield, and gasket. We'll see tomorrow if it worked



Brad,
The squish numbers seem to indicate you could have run the saw w/o the base gasket just for the heck of it...just out of curiosity. Of course, the difference (as you mentioned earlier) may not have been fully manifest w/o bigger wood to test with.


----------



## blsnelling (Sep 6, 2009)

litefoot said:


> Brad,
> The squish numbers seem to indicate you could have run the saw w/o the base gasket.



Not possible. The piston would have been nearly hitting the squish band with only .004"-.005" clearance.


----------



## pepsifreak28 (Sep 7, 2009)

*muffler mods*

blsnelling im in ohio east of columbus are you around columbus?

I wanted to say nice work on the mods blsnelling
I was wondering if you have ever heard of javapipe?
I seen some hotsaws with tuned pipes and I think it would be awesome if you could fit a tuned pipe on a work saw maybe wrap it underneath the saw someway I'm not sure if its possible to put a smaller version of a tuned pipe and have it be very effective but javapipe would tell you the size of the openings and such to build one provided you do some port mapping and such I use to have some computer programs that would theorie craft engines as well a lot of the rc boaters mod 2 strokes with tuned pipes and such check some of the insanity 
http://www.youtube.com/watch?v=zxWiFz0t19g
http://www.youtube.com/watch?v=0lHO7LvPf2c&feature=related


----------



## MCW (Sep 7, 2009)

blsnelling said:


> It would be nice to see them running the same chain in the same wood for a good comparison.



I forgot to reply to you earlier Brad but will post vids comparing both 7900's with the same brand new chains on the same log on a different property. I have about 25-30 tonne of nice even Eucalypt logs up to maybe 40" at the most. The problem with the Casuarinas I'm cutting is the wood density is extremely inconsistent even in the same logs. They have pockets of water, old leaf debris etc and generally the logs are uneven in shape.
Unfortunately won't be able to do this for a few weeks but will post vids then for sure.


----------



## MCW (Sep 13, 2009)

Back again with another vid of the new 7900. I was hoping to do some decent comparisons over the weekend in same sized wood with 32" bars between my stock 7900 and my modded 7900.
Unfortunately the weather was an absolute shocker with massive winds and duststorms on the inlaw's farm. I took a few vids out in the open on some 36" odd RedGum logs but the wind was that bad I was eating and being blinded by nearly every woodchip that came off the saw. It was impossible to get a decent angle on the log without being choked by chips. These logs were still relatively green and not much dust so I didn't get the chance to give the new HD filter a workout as planned.
I did manage however (for a bit of a laugh) to find a more sheltered area, stick the 42" bar on the 7900 off my 3120, and bury it in a Redgum log with 3/8" Carlton non skip semi chisel (7 pin sprocket). For interest this particular log isn't as tough as it would be when dry but still pretty solid.
Before anyone says anything, no the oiler couldn't keep up, but I was impressed nonetheless. This is one very strong saw and is getting stronger with every tank...

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/XswACPavEuk&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/XswACPavEuk&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## mdavlee (Sep 13, 2009)

Nice video, looks like that saw has plenty of power.


----------



## 7sleeper (Sep 13, 2009)

real nice vid!

7


----------



## blsnelling (Sep 13, 2009)

Nice! I knew you'd be giving this saw a workout. But 42"? Wow


----------



## MCW (Sep 13, 2009)

blsnelling said:


> Nice! I knew you'd be giving this saw a workout. But 42"? Wow



Best I could do at the time Brad 
Will get that 32" comparo up ASAP.


----------



## parrisw (Sep 13, 2009)

That's pretty cool. 42" Wow. That would give my 395's and 394's a workout.


----------



## CHEVYTOWN13 (Sep 13, 2009)

Good Show


----------



## MCW (Oct 16, 2009)

Back again with another video of the modded 7900. Have been keeping a nice lump of Chinese Elm out the back to mill at a later date. Hadn't noticed but some rain we had recently had caused the ends of the log to split. Decided to cut off the ends and recoat with a wax timber emulsion. In the process decided to blow some cobwebs out of the 3120 (it's feeling neglected!) and give it a run against the 7900. Both saws wearing the same 32" bar and .404" non skip semi chisel chain.
My 3120 was a few seconds faster on average but good show by the 7900 I think. This particular Chinese Elm tree was/is tough to cut and very dense. Hard to get a smooth cut as you can see.
For those who haven't run .404" it is very bitey compared to 3/8" 
Both saws running a 7 tooth sprocket...


<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/0NsZyuVDQOM&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/0NsZyuVDQOM&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

I also am starting to finally get my head around Window's Movie Maker.


----------



## stihlboy (Oct 16, 2009)

dang that 7900 runs good


----------



## blsnelling (Oct 16, 2009)

Not bad at all for a 79cc saw against a 120cc saw!


----------



## MCW (Oct 16, 2009)

I wish I could properly explain just how tough that Chinese Elm is to cut. Its like the chain just wants to bounce clean out. I dropped this tree originally with the 3120, 42" bar, and full chisel chain. The scarf and backcut was a saw stalling nightmare and it was the first tree I dropped with the 3120. I actually thought something was wrong with my new saw! Has a lot of tight twisty grain which doesn't help I suppose and I've since learned that this particular tree is one of the toughest timbers I've ever cut.
The 7900 does a good job though, which is why the 3120 is feeling neglected. I have to be honest, if it wasn't for the mill and my chainsaw obsessive compulsive disorder I'd probably consider selling the 3120.


----------



## MCW (Oct 16, 2009)

blsnelling said:


> Not bad at all for a 79cc saw against a 120cc saw!



Particularly for a poorly built and badly assembled saw Brad 
I'm lucky one of those self tapping screws didn't fall out onto the chain and have my eye clean out!
Heh heh, you know where I'm coming from


----------



## Jtheo (Nov 8, 2009)

Nice video, thanks


----------

