# The Dolmar 7910 - Snellerized Style



## blsnelling (Sep 12, 2015)

It's been 5-6 years since I last modded a Dolmar 7900. I never was quite satisfied with the results I was getting at that time. I've followed MillerModSaws threads very closely. I've talked to Randy and Poleman as well. I owe a lot of this build to them. I've taken what I learned from them and applied it to this new 7910. Thanks guys!

Here's the saw as I received it, straight from our friend FordF150.


























Those of you that have followed some of the other 7910 threads will know that they have a very restrictive chamber in the muffler. This chamber actually protrudes from the muffler and inserts into the exhaust port. The muffler must be uncrimped and this chamber removed. I then cut the chamber and the protrusion from the thick metal flange they're welded to. I ground most of the grooves from the exhaust port. This meant a LOT of port matching on the thick flange of the muffler. Lots of extra work on this saw in the muffler and exhaust port!


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## blsnelling (Sep 12, 2015)

I then proceeded to install a 272XP coil. No unlimited coil is available for the 7900/7910, so I chose to make the mods necessary to run this unlimited 272 coil. The stock coil is limited to 12,800, IIRC. In addition to being much harder to tune, that's just way to close to the RPMs this saw will want to turn.











The 272 coil fires at a much different time than the stock coil. For that reason, the key must be ground from the flywheel and then advanced approximately 30°. I have marked the case at 0°, 25°, 30°, and 35°. You'll notice that I've filed the one fin to a point, to make timing adjustments more accurate and easier to set.


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## Deets066 (Sep 12, 2015)

Nice lookin grinding there B Rad


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## blsnelling (Sep 12, 2015)

There are some more mods coming for this saw. I have the HD filter kit on order. This kit is only available in gloss black and wouldn't look that good with the flat black cylinder cover. So, some asthetic mods are going to be done to this saw as well. You'll just have to wait to see what that's all about


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## Ironworker (Sep 12, 2015)

Nice, I got nuttin doing tonite so keep it coming or I'll have to go on Facebook and post my Athiest/anti-religion stuff.


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## Stihl 041S (Sep 12, 2015)

Nice work Ol Buddy.


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## blsnelling (Sep 12, 2015)

Ironworker said:


> Nice, I got nuttin doing tonite so keep it coming or I'll have to go on Facebook and post my Athiest/anti-religion stuff.


Lol. That's all I've got for now. I will tell you this, I saw 15,100 while playing with the tune


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## Ironworker (Sep 12, 2015)

blsnelling said:


> Lol. That's all I've got for now. I will tell you this, I saw 15,100 while playing with the tune


Good stuff.


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## stihlaficionado (Sep 12, 2015)

blsnelling said:


> There are some more mods coming for this saw. I have the HD filter kit on order. This kit is only available in gloss black and wouldn't look that good with the flat black cylinder cover. So, some asthetic mods are going to be done to this saw as well. You'll just have to wait to see what that's all about


You going to etch your name on the cylinder fins?


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## blsnelling (Sep 12, 2015)

stihlaficionado said:


> You going to etch your name on the cylinder fins?


Good idea


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## stihlaficionado (Sep 12, 2015)

blsnelling said:


> Good idea


I'd do each letter in a different color


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## redfin (Sep 12, 2015)

Looks good Brad. Lots of Dolmar poppin up around here lately.


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## blsnelling (Sep 12, 2015)

redfin said:


> Looks good Brad. Lots of Dolmar poppin up around here lately.


We've got a couple good dealers on the forum now. That makes a real difference.


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## nnero (Sep 12, 2015)

Oooo this is exciting. I'm liking all the Dolmar stuff going on lately. Those spikes are huge!! Great job, can't wait to see more (and the Solo twin)!


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## Babaganoosh (Sep 12, 2015)

Oddly enough I just got to really run my dolmar/makita 6421 today. I was very pleased. Probably do the 79cc upsize over the winter.


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## Adirondackstihl (Sep 12, 2015)

The 7900 at the bottom with the 20" Cannon is my PTM7900. The AF cover was brandy new gloss. The top cover was nasty stained faded red. Few coats of Fusion gloss black and she matched the AF cover real nice.
I have one more saw in the pic, can you find it?


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## MillerModSaws (Sep 12, 2015)

I know your not particularly found of these saws. Has that changed any?


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## Poleman (Sep 12, 2015)

Good job Brad!!!!! Don't the r's make you grin compared to stock???
You really spent some time on the exhaust.....looks GREAT!!!


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## CR888 (Sep 12, 2015)

That trailer of saws shows how long term cad can be managed. lts not the point that there is more saws than logs of wood to cut.


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## Adirondackstihl (Sep 12, 2015)

CR888 said:


> That trailer of saws shows how long term cad can be managed. lts not the point that there is more saws than logs of wood to cut.


There was/is still plenty of wood there to cut!


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## luckydad (Sep 12, 2015)

5100 to the left ??


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## Stihl working hard (Sep 12, 2015)

blsnelling said:


> It's been 5-6 years since I last modded a Dolmar 7900. I never was quite satisfied with the results I was getting at that time. I've followed MillerModSaws threads very closely. I've talked to Randy and Poleman as well. I owe a lot of this build to them. I've taken what I learned from them and applied it to this new 7910. Thanks guys!
> 
> Here's the saw as I received it, straight from our friend FordF150.
> 
> ...


Very nice work there Brad


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## Adirondackstihl (Sep 12, 2015)

luckydad said:


> 5100 to the left ??


What gave that away?


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## blsnelling (Sep 12, 2015)

MillerModSaws said:


> I know your not particularly found of these saws. Has that changed any?


If it runs anything like I think it is, I'll be tickled pink.



Poleman said:


> Good job Brad!!!!! Don't the r's make you grin compared to stock???
> You really spent some time on the exhaust.....looks GREAT!!!


That was the hardest part of this build. Of course, the first time is always the hardest, but it is a lot of work.


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## Adirondackstihl (Sep 12, 2015)

Any inside pics?


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## Hinerman (Sep 12, 2015)

Adirondackstihl said:


> What gave that away?



I see what you did there....


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## 166 (Sep 12, 2015)

CR888 said:


> That trailer of saws shows how long term cad can be managed. lts not the point that there is more saws than logs of wood to cut.






Here's a blurry panoramic view of some of the damage.


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## 166 (Sep 12, 2015)

Adirondackstihl said:


> The 7900 at the bottom with the 20" Cannon is my PTM7900. The AF cover was brandy new gloss. The top cover was nasty stained faded red. Few coats of Fusion gloss black and she matched the AF cover real nice.
> I have one more saw in the pic, can you find it?



Ain't you gotta before pic of "Wally" in the back of the truck?


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## Adirondackstihl (Sep 12, 2015)

166 said:


> Ain't you gotta before pic of "Wally" in the back of the truck?


After......




Before.....


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## Deets066 (Sep 12, 2015)

Adirondackstihl said:


> What gave that away?


"I have a potty mouth"


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## CapitaineHaddoc (Sep 13, 2015)




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## drf255 (Sep 13, 2015)

Brad,

The work looks top notch as usual. Port beautiful. 

How did you calculate the needed timing on the saw with the coil? Can you give us some insight into the calculations, what the position the magnets need to be on the coil to fire it, etc...

Did you measure where it fired in relation to the flywheel on a 272 first, then make similar alignment of the magnets?


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## stihlaficionado (Sep 13, 2015)

Adirondackstihl said:


> After......
> 
> 
> 
> ...


Wow…ya done really good


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## benp (Sep 13, 2015)

Good work as always Brad!!

The ease of tuning was the main reason that I went with the unlimited coils in both of mine.


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## fordf150 (Sep 13, 2015)

Can someone explain why the manufactures go with limited coils? Seems to me that an unlimited coil would be cheaper to produce, easier for techs to tune, more reliable since there would be less circuits inside the coil. 

Must be a reason since just about every manufacturer is switching to them


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## wde_1978 (Sep 13, 2015)

fordf150 said:


> Can someone explain why the manufactures go with limited coils? Seems to me that an unlimited coil would be cheaper to produce, easier for techs to tune, more reliable since there would be less circuits inside the coil.
> 
> Must be a reason since just about every manufacturer is switching to them


If setup too lean they still burn up but don't turn 20k and dismantle themselves explosion style dragging law suits in their wake?!


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## Poleman (Sep 13, 2015)

I think it would be for the unskilled tweezers who think a totally leaned saw is faster. I've seen this tim and again on Stihl 044/046's where the saws were tuned to just scream.....while they lasted.
I think it's a way of manufacturers to help their equipment last longer in unskilled hands and reduce warranty work.

Just kinda my thoughts on it.....

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## blsnelling (Sep 13, 2015)

Adirondackstihl said:


> Any inside pics?


I do not. It's sporting a .020" popup and cylinder base cut. Porting was a combination of what Miller and MM do, with a little of my own flair added in.



drf255 said:


> Brad,
> 
> The work looks top notch as usual. Port beautiful.
> 
> ...


Here's how I do it. http://www.arboristsite.com/community/threads/how-to-make-your-7900-or-681-non-rev-limited.116556/


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## Paragon Builder (Sep 13, 2015)

Hey Brad, I just read through that thread. You mentioned you adjust timing until you achieve max rpm. Is this how you find the best timing on all saws? Is this a safe way to do it? And besides rpm starting to drop, how do you or I know it's got too much advance? I always wondered when advancing my saws if I would know if it was too much by how it ran, or if I'd find out when I cooked it?[emoji12] 
Hasn't stopped me though!


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## blsnelling (Sep 13, 2015)

I was advised to set this saw to 30*, which I did. Throttle response is lightning quick and it runs great. I let someone else do the homework on this one


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## Poleman (Sep 13, 2015)

When I seen Brads coil mod from a few years back I wasn't really hep on the idea of separating the parts and reinstalling. Yes it made it easier to mount but not a thing I don't feel everyone can do.....so I came up with what would be needed to make the intact 272 coil work. A little messaging of the mounting holes and a little patients running the spark plug wire. Then I started at 27° like Brad had used and went from there when the saw was sluggish. I went until throttle responce was lightning quick and if the saw started good.
I have hade to advance particular saws slightly more.....that may be the saw or it may have been my marking. It's an easy mod and easy to change timing.....if you mark well.
I have also been marking flywheel for original timing and modded timing if any reason the flywheel needs pulled or stock coil reused. 

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## David Young (Sep 13, 2015)

You use a 4 jaw and off set pop up?


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## Paragon Builder (Sep 13, 2015)

Poleman said:


> When I seen Brads coil mod from a few years back I wasn't really hep on the idea of separating the parts and reinstalling. Yes it made it easier to mount but not a thing I don't feel everyone can do.....so I came up with what would be needed to make the intact 272 coil work. A little messaging of the mounting holes and a little patients running the spark plug wire. Then I started at 27° like Brad had used and went from there when the saw was sluggish. I went until throttle responce was lightning quick and if the saw started good.
> I have hade to advance particular saws slightly more.....that may be the saw or it may have been my marking. It's an easy mod and easy to change timing.....if you mark well.
> I have also been marking flywheel for original timing and modded timing if any reason the flywheel needs pulled or stock coil reused.
> 
> Sent from my SAMSUNG-SM-G900A using Tapatalk


So Rich, do you stop advancing when it feels good, or is there a point when you know you went to far?


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## Poleman (Sep 13, 2015)

Dan,
That pretty much what I do. I work for the fastest throttle responce with the least amount of timing. The magic number seems to be 30°, but have went to 33° on a couple. You'll know right away on initial start up if it's right or needs bumped.

If you over advance you loose power and responce, so when the saw is as fast as you can blink I stop.....lol


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## Paragon Builder (Sep 13, 2015)

Gotcha. Thanks Rich. 
I was kinda worried that the saw may feel great, but be detonating and cook the saw.
Sounds like I'm good on the ones I've done.
I guess someday I'll have to keep going on an older saw just so I know what too much is like...


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## Poleman (Sep 13, 2015)

You can do it on any one to see how it feel....it won't take long for you to shut it off and put the numbers where they were. Trust me....you won't run it long enough to hurt it.....it's that much different.....


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## computeruser (Sep 13, 2015)

Very interesting thread. Looking forward to the ending and videos!

You guys, and I am referring to MillerModSaws and Brad in particular, are going to get my CAD all flared back up again with these 7910 builds and the generally renewed interest in Dolmar saws.


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## fordf150 (Sep 13, 2015)

Poleman said:


> You can do it on any one to see how it feel....it won't take long for you to shut it off and put the numbers where they were. Trust me....you won't run it long enough to hurt it.....it's that much different.....


 

You run into any that ran good but the initial timing was to much making the saw hard starting


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## benp (Sep 13, 2015)

fordf150 said:


> You run into any that ran good but the initial timing was to much making the saw hard starting



Mine are a little harder to start than the 394 but to me it's negligible considering what awaits on the end of that trigger once it's lit.


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## Poleman (Sep 13, 2015)

Not really. Most the time it helps (if set right) to start the saw. The not a hard starting saw ( unless your pulling the rope on a MMS @ 225 lb compression) and even at that they pop right off.

I've had starting issues after a coil mod and carb mod but it's ALWAYS been the carb. Usually being to rich. That's things I sort out when adjusting and setting the carbs I build. I try to get all the query out.

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## Poleman (Sep 13, 2015)

The good starting is ressurance to me the timing is right, if ever thing else is what I like and the saw starts hot/cold with no Hassel we're good.

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## benp (Sep 13, 2015)

redfin said:


> Looks good Brad. Lots of Dolmar poppin up around here lately.



I think that's it great that the "Dol-what's" are coming back into focus.

I really like the fact that there are more tinkering with the unlimited coil now.

When Eric offered me that option a couple years ago I jumped on it just for tuning purposes. I can't hear the sound differences to tune by ear worth a lick but I can read a tach.


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## MillerModSaws (Sep 13, 2015)

Finished the 7310 up today. How's she sound comparitively speaking?


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## Stihl working hard (Sep 14, 2015)

Adirondackstihl said:


> After......
> 
> 
> 
> ...


Awesome job on the saw


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## Stihl working hard (Sep 14, 2015)

fordf150 said:


> Can someone explain why the manufactures go with limited coils? Seems to me that an unlimited coil would be cheaper to produce, easier for techs to tune, more reliable since there would be less circuits inside the coil.
> 
> Must be a reason since just about every manufacturer is switching to them


Maybe warranty on the sawjust my 2 cents worth


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## David Young (Sep 14, 2015)

I think when they are worried about the crank. 3120 064/066


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## Greny (Sep 14, 2015)

CapitaineHaddoc said:


>



Your ps 7900 needs a porting job


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## CapitaineHaddoc (Sep 14, 2015)

Greny said:


> Your ps 7900 needs a porting job



Yeah, I think about it. I'll send the jug with a 346 jug to have them both ported when the builder have the time to do it.


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## Greny (Sep 14, 2015)

CapitaineHaddoc said:


> Yeah, I think about it. I'll send the jug with a 346 jug to have them both ported when the builder have the time to do it.




Haha , I was right copain [emoji28]


Envoyé de mon iPad en utilisant Tapatalk


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## blsnelling (Oct 7, 2015)

I should probably wait for the finished product, but had to share these! BOOM!!!


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## Poleman (Oct 7, 2015)

Man.....THAT'S SAWEET!!!!!

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## blsnelling (Oct 7, 2015)

That's black oxide on the muffler, dawgs, and bar nuts. It didn't take on the muffler bracket and plugs, so they're only painted.


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## Poleman (Oct 7, 2015)

That really unique and eye catching......will look fast not even running!!! Lol
Black oxide????? Is that similar to parkerizing? Looks like it has a slight satin finish.....look good.....REALLY GOOD!!!!

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## fordf150 (Oct 7, 2015)

Looks good!!!!!!!


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## blsnelling (Oct 7, 2015)

I think parkerizing puts a coating on the item. This is more less just stained black. It's used in the machine tool industry for corrosion protection.


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## Poleman (Oct 7, 2015)

Kinda like blueing on a firearm? ?? 

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## blsnelling (Oct 7, 2015)

Poleman said:


> Kinda like blueing on a firearm? ??
> 
> Sent from my SAMSUNG-SM-G900A using Tapatalk


Very much like that.


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## porsche965 (Oct 7, 2015)

I'm thinking I need another "Painted Saw" lol. Very nice Brad.


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## Rev (Oct 7, 2015)

Nice but why does it have on a helmet?


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## blsnelling (Oct 7, 2015)

blsnelling said:


> I should probably wait for the finished product, but had to share these! BOOM!!!


These upgrades should help in the appearance department


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## blsnelling (Oct 10, 2015)

She's done, and lookin' mean!


























Sure beats what I started with!


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## chris zautner (Oct 10, 2015)

Nice


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## chris zautner (Oct 10, 2015)

who dipped all the plastics for you?


blsnelling said:


> She's done, and lookin' mean!
> 
> 
> Sure beats what I started with!
> QUOTE]


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## porsche965 (Oct 10, 2015)

Looks like it's doing 10k rpms just sitting there!


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## blsnelling (Oct 10, 2015)

chris zautner said:


> who dipped all the plastics for you?


Pro-line Hydrographics


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## blsnelling (Oct 10, 2015)

porsche965 said:


> Looks like it's doing 10k rpms just sitting there!


20K


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## porsche965 (Oct 10, 2015)

The color disguises that funny looking HD air filter cover somewhat. Much better.


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## Poleman (Oct 10, 2015)

Well....you sure can't run it now......IT"S A SHOW PIECE!!!!! I could sure find a place to DISPLAY it!!!!!


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## Tractorsaw1 (Oct 10, 2015)

It's sure got the bling- waitin to see it zing......[emoji3]


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## blsnelling (Oct 10, 2015)

Poleman said:


> Well....you sure can't run it now......IT"S A SHOW PIECE!!!!! I could sure find a place to DISPLAY it!!!!!


It will be run. Videos will be coming after she's broke in a bit.


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## Poleman (Oct 10, 2015)

I know you've run it.... probably not in wood, but any indications and expectations??


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## blsnelling (Oct 10, 2015)

I will be making some test cuts with it this week. Should that go well, I will giving it to a friend to put some run time on it. I know WOT RPMs aren't what cut wood, but I'm optimistically encouraged to see it tune as high as 15,150 and still have some 4-stroking.


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## Four Paws (Oct 10, 2015)

Brad, did Rich build your carb?


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## Poleman (Oct 10, 2015)

Nope....just gave him the how too.......

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## blsnelling (Oct 11, 2015)

Four Paws said:


> Brad, did Rich build your carb?


He did not. The saw has perfect manners as is. I'm hesitant to mess with it. Idle is perfect. Throttle response is instant. Tuning is easy.


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## Terry Syd (Oct 11, 2015)

OK Brad, you don't want to mod a carb that you know is 'working'. However - Rich, if you have a modded carb to loan Brad, he just might appreciate the opportunity to try something different. You know, stock carb compared to a modded carb? That way he can still have his stock carb to fall back on. It also allows him to compare the two carbs on a known saw.


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## blsnelling (Oct 11, 2015)

I would love to try a modded carb, just don't want to take a chance messing up what's already running great, and not mine.


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## wde_1978 (Oct 11, 2015)

blsnelling said:


> She's done, and lookin' mean!
> 
> 
> 
> ...



Wow, just WOOOOW .... 

Keep the saw , how much for the covers and the dogs - those should help scare some trees to death and fall over by themselves! 

Saying the saw looks cool is just wrong as she is burning up just sitting there!
Great work!


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## Locust Cutter (Oct 11, 2015)

It looks like it MIGHT give a 346 a run for it's money... LOL
That saw looks great! I wouldn't mind having a ported 7900/10 but I may just pickup a ported 390xp and call it good. I DO like the feel of the 6400-7900 family of saws though.


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## Terry Syd (Oct 11, 2015)

blsnelling said:


> I would love to try a modded carb, just don't want to take a chance messing up what's already running great, and not mine.



Thinking about it, the postage back and forth would probably pay for a cheap Chinese carb that you could mod. Putting Rich on the spot to loan you a carb seems like a silly suggestion, sorry I brought up the idea now


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## Poleman (Oct 11, 2015)

Not a bad idea Terry....I think it's good!! Brad does in depth comparisons and is straight up on things. If it good he says so and if it's bad...he say so....that's what's needed to see if they really work. My testing is rather seat of the pants and unscientific. Most call it the Redneck way!!! Lol


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## Poleman (Oct 11, 2015)

Brad, pm me your address and I will send a carb Tuesday if you'd like to try one. I will drill and test one tomorrow and get it out Tuesday....hopefully be there Friday.

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## blsnelling (Oct 11, 2015)

Sounds great Rich. Just let me know how much shipping is. Thanks.


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## fordf150 (Oct 11, 2015)

@Poleman how would that carb you sent me react on a ported saw? I have it laying on the shelf. Installed the original carb back on mine when I decided to sell it. Was going to install it on my future 7910H but if it will do brad some good it will get there a few days sooner.


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## Poleman (Oct 12, 2015)

Nate, I believe your carb if first gen....I have made some improvements since than to make it tune like like oem.
It would work great since 1 gens usually ran a little rich.


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## fordf150 (Oct 12, 2015)

@blsnelling if you want mine I will send it out today


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## blsnelling (Oct 12, 2015)

I'll defer to Rich's recommendation.


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## Poleman (Oct 12, 2015)

There's nothing wrong with 1st Gen, but newer tune more like oem and easier to tune. Brad I will get you the carb I have and Nate, I will send you an updated one.....I think you'll notice a difference. Nate if your going to put it on a ported saw let me know, I'll go bigger!!


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## fordf150 (Oct 12, 2015)

Poleman said:


> There's nothing wrong with 1st Gen, but newer tune more like oem and easier to tune. Brad I will get you the carb I have and Nate, I will send you an updated one.....I think you'll notice a difference. Nate if your going to put it on a ported saw let me know, I'll go bigger!!


no porting for me. I am building a 7910H stock. I dont use one enough to justify porting. I try to stick to my 421 as much as possible. No splitter anymore so everything i cut has to fit through the processor and that limits me to 20-22" if they are perfect straight with no knots.


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## Poleman (Oct 12, 2015)

I'll send you the smaller one. Works on a ported saw too!!!

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## VinceGU05 (Oct 12, 2015)

blsnelling said:


> She's done, and lookin' mean!
> 
> 
> 
> ...



while it looks great i would prefer to see it carbon fibre style. personal choice. hey brad, water ya grass; its drying out


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## blsnelling (Oct 12, 2015)

VinceGU05 said:


> hey brad, water ya grass; its drying out


I know


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## Poleman (Oct 13, 2015)

Can't blame Brad....look at the heat the saws putting out!!!!!!

Besides, its fall time to cut wood and end yard work....


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## benp (Oct 13, 2015)

blsnelling said:


> He did not. The saw has perfect manners as is. I'm hesitant to mess with it. Idle is perfect. Throttle response is instant. Tuning is easy.



That's how mine are. 

But.....there's that little voice rattling around questioning how much better a modded carb would be.


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## Terry Syd (Oct 14, 2015)

Hopefully Brad will give us his time to really test the difference. If he doesn't have big enough wood, then maybe an 8-pin might substitute for an extra load.

Rich has noticed a difference between the jetting on stock and ported saws. I expect that is because the torque peak has been raised on the ported saw and the low speed circuit has a bigger gap to fill before peak torque. Rich has bridged the gap with a bit more low speed flow.

A carb swap is an easy mod for most guys. Do a muffler mod and then a carb swap and most of the EPA issues have been eliminated.

There is still the issue of excess hydrocarbon emissions that Blair refers to in his work. The factories are running around 2 degrees less blowdown to help control them. Not a biggie for most wood cutters, but a port job and extra compression (nitrogen oxides emissions) changes the picture on performance for the enthusiast.

I'm looking forward to the comparison of the stock EPA carb to the modded carb. - Brad, put some freaking load on the saw and make the saw WORK.


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## blsnelling (Oct 16, 2015)

I finally get to go cut some wood again, back up at our church camp. I'll be putting this new 7910 to work and getting some videos tomorrow. I'm looking forward to getting back out to work the saws a bit. I'm going to have some time to play with the modded carbs a bit as well.

Here are a couple of the trees already down.


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## SCHallenger (Oct 16, 2015)

That church camp has been a great "test track" for you. I'm looking forward to the vids!


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## Locust Cutter (Oct 16, 2015)

Hell if I was closer, I'd love to come play. That ought to be some fun.


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## blsnelling (Oct 16, 2015)

Well, I'm pretty bummed. I got a call from the camp care taker, and several guys showed up today and already got it all done  Instead, I'm going to venture over near Indianapolis to drop a tree for my cousin's church that they've been on me to do for several months now. At least I still get to run this saw


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## SquareFile (Oct 16, 2015)

Now who in there right mind wound have a saw hydro dipped.


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## porsche965 (Oct 16, 2015)

SquareFile said:


> Now who in there right mind wound have a saw hydro dipped.



Me. lol


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## fordf150 (Oct 16, 2015)

porsche965 said:


> Me. lol


I would do it to. That saw may end up with somewhat of a twin. I like the muffler and spikes. Really like the hood. Will have me a saw like that one day


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## Poleman (Oct 16, 2015)

Me three......that saw is HOT!!!! LOL

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## CR888 (Oct 16, 2015)

l think Brad will like the modded carb, little gains here and there all add up to make the best saws. Very nice looking saw! l am looking forward to hear from Brad about the carb's performance. l think he should run the unmodified carb for a few tanks first to really notice the differences.


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## Terry Syd (Oct 17, 2015)

Or maybe the other way around - run the modded carb to get used to having the torque on tap and developing a cutting technique with the saw that can make use of the torque - then swapping to the stock carb and noticing how 'weak' the stock carb is and having to change techniques to compensate.

Either way, it will be interesting to get his unbiased impressions as this will be his introduction to using a modded carb on a work saw (as pretty as it may be).


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## CR888 (Oct 17, 2015)

l really want to do these carb mods to my 681solo, it has a walbro carb. l think it would be good for a 6400 l have too. l got the pin vise and micro drill set.....then chickened out!lol l think before l operate on my oem carbs some pratice on a cheap china am carb may be best. These exact modds are well described in Graham Bell's performance tuning and he sugests exactly what you guys are doing in the same way. Theres a few good diagram pics explaining things well.


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## Terry Syd (Oct 17, 2015)

These diaphragm carbs are a separate breed to something like a Mikuni for a bike. The same relative fuel flow concepts apply, but the carb configurations/circuits are completely different and more difficult to get your head around.

The cheap Chinese carbs are a good way to 'make some mistakes' and not blow out the budget.

The Walbros require a different approach to the Zama 'twin jets'. If you get a kit of a selection of Walbro springs you'll probably find it much easier to dial in the carb. You may not even have to drill the transition holes, just tweak the low speed needle to where you want it and then find a spring to clean up the idle and transition. If you can't fix it with the spring, then drill and go back to the springs, repeat if necessary.


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## blsnelling (Oct 18, 2015)

I'm sorry to disappoint, but no video. All of my work saws were setup to work with yesterday. What I had left was a 32" Tsumura L&T, and it was way too long and nose heavy for the 7910. The chain I had on it was horrible. Rather than misrepresent the saw, I'll wait until I have the chance to set it up properly.


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## Four Paws (Oct 18, 2015)

blsnelling said:


> What I had left was a 32" Tsumura L&T, and it was way too long and nose heavy for the 7910.



Imagine if you had a regular weight bar! Does the 461 balance better with a 32?



blsnelling said:


> The chain I had on it was horrible.



Why was it horrible...was it Stihl chain? Or, filed by a cull?


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## SCHallenger (Oct 18, 2015)




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## bwalker (Oct 18, 2015)

Terry Syd said:


> Hopefully Brad will give us his time to really test the difference. If he doesn't have big enough wood, then maybe an 8-pin might substitute for an extra load.
> 
> Rich has noticed a difference between the jetting on stock and ported saws. I expect that is because the torque peak has been raised on the ported saw and the low speed circuit has a bigger gap to fill before peak torque. Rich has bridged the gap with a bit more low speed flow.
> 
> ...


Two strokes have natural low NOX emmissions. This is due to the way they are scavenged and the residual exhaust gas always present in the conustion chamber. Sort of like built in EGR.


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## blsnelling (Oct 18, 2015)

Four Paws said:


> Why was it horrible...was it Stihl chain? Or, filed by a cull?


Yes, it was filed by a cull, lol.


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## Tractorsaw1 (Oct 18, 2015)

Bummer, first someone cuts up the wood & then no video [emoji35]


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## blsnelling (Nov 4, 2015)

Finally! The long awaited video. I had a chance to run the saw again last night. Since last time, I've gone back in and done more port work. It made a difference. I've also got a better chain on it this time. Even though brand new, it's running neck and neck with a well broken in EHP 7900. That makes me happy


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## Poleman (Nov 4, 2015)

Nice videos Brad, and a good comparison of popular saws!!!!

Sent from my SAMSUNG-SM-G900A using Tapatalk


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## blsnelling (Nov 4, 2015)

I plan to play with the carbs next.


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## smokey7 (Nov 4, 2015)

Absolutely perfect video that's exactly what i like to see.


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## Jeffkrib (Nov 5, 2015)

So Brad whats you humble opinion on that 7910? From here it looks like you can lean on it quite heavily.
How would you rank it against a ported 461' 576 and 372 for a heavy handed user with a 28 inch bar?
Ta
Jeff


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## David Young (Nov 5, 2015)

blsnelling said:


> Lol. That's all I've got for now. I will tell you this, I saw 15,100 while playing with the tune



brad does the warning in your picture concern you at all?


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## David Young (Nov 5, 2015)

fordf150 said:


> Can someone explain why the manufactures go with limited coils? Seems to me that an unlimited coil would be cheaper to produce, easier for techs to tune, more reliable since there would be less circuits inside the coil.
> 
> Must be a reason since just about every manufacturer is switching to them


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## David Young (Nov 5, 2015)

nice looking saw btw, clean looking work.


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## blsnelling (Nov 5, 2015)

David Young said:


> brad does the warning in your picture concern you at all?


Nope


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## David Young (Nov 5, 2015)

I dont know why they put the warning I have never heard of anything going wrong with them. maybe the magnets get dizzy.


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## David Young (Nov 5, 2015)

oh what were the stock numbers? did you stay close to the stock numbers?


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## blsnelling (Nov 5, 2015)

I don't have the numbers in front of me, but they weren't changed much.


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## David Young (Nov 5, 2015)

its amazing how well they run and the numbers don't make conventional sense. I don't understand why the other companies didn't try to mimic the success.


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## blsnelling (Nov 26, 2015)

I'm home with Shingles while the rest of the family is at my Mom's for Thanksgiving. While I don't feel all that great, I don't feel too poorly to mess around with a saw 

I had a few more mods to try on this saw and did so last night and today. I'm very pleased with the final results. I slightly altered exhaust and intake port timing. I added a much larger Walbro RWJ4 carb. I bumped the ignition timing another 2°-3°. And, I added a second port to the face of the muffler. I also used Aluminum Black to blacken the cylinder. I tried using it on the handle, but it didn't look that great, so I painted it. It's in the oven curing now. I also decided to paint the muffler. The black oxide didn't take very well on it at all.

Here's the saw in it's final configuration, before the additional cosmetic work. Yes, it's on the lean side, but quickly begins to 4-stroke in the cut and not run as well if run much richer at all. She's tuned to 14,700 after coming out of the last cut. This is a Stihl RSC chain, round filed, with the rakers set rather aggressively.


Here's the additional muffler port.





Here's the blackened cylinder.


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## blsnelling (Nov 26, 2015)

Here's to show you what only 2°-3° of ignition timing difference can make! BTW, this was before the additional port in the muffler. It seemed to benefit the loaded cut the most.

+32°


+29°


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## Poleman (Nov 26, 2015)

Brad, hate to hear about your Shingles...hope you get better soon.

How and what did you use to mount the RWJ carb and still use the HD filter??


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## blsnelling (Nov 26, 2015)

Poleman said:


> How and what did you use to mount the RWJ carb and still use the HD filter??


All factory parts. The carb sets at an angle since the mounting holes aren't level. I had to heat and bent the throttle cable sheath holder. The biggest obstacles were limiting the travel on the fast idle arm of the choke, so that it wouldn't come back up and rest on the rubber filter boot. I actually drilled and tapped a very small hole in the side of the carb. I did the same thing to limit the over travel of the choke. After removing the baffle in the venturi, I goes past level. There are two remaining issues. In order to make the choke work at all, the arm has to be flipped up, rather than down as it comes. That means that to choke the saw, you push the choke rod in. For run, you have to pull it out. I don't like that, but I don't see any other solution with this carb. The only other thing is it idles too high and can't be adjust down. The notches in the throttle plate are much larger than on the stock carb. It's simply getting too much air. To get it any lower would require making a new throttle plate. It's idling about 3,300 right now, which isn't really an issue. It runs great in every way though. It idles great, has great throttle response, spools up quickly, and tunes easily.


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## SquareFile (Nov 26, 2015)

Removing the divider in the carb necessary?


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## blsnelling (Nov 26, 2015)

SquareFile said:


> Removing the divider in the carb necessary?


I'm not sure. I have always removed them, but think I've heard of others that have not. This might be a good application not to. What's your experience with them?


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## 94BULLITT (Nov 26, 2015)

David Young said:


> I dont know why they put the warning I have never heard of anything going wrong with them. maybe the magnets get dizzy.



They can explode.


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## MillerModSaws (Nov 26, 2015)

I gotta ask how big a difference did just the carb make? Did you check the rpm in the cut by chance?


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## blsnelling (Nov 26, 2015)

MillerModSaws said:


> I gotta ask how big a difference did just the carb make? Did you check the rpm in the cut by chance?


I intended to, but got caught up with making all the changes I had in mind last night and did not. I would go back to the factory carb, but ruined it trying to bore it out.

I'm now holding as high as 13,000 in the cut with a light load on a very aggressive chain. It's over 12,000 with a medium load.


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## SCHallenger (Nov 26, 2015)

Wow!! You really stood on your head to get that baby running the way you wanted! Looks & sounds like it was worth it!
Bummer on the shingles. Reminds me that I should get the vaccine, since I am a likely candidate.. I hope you get over this episode soon.


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## Poleman (Nov 26, 2015)

Looks like I may be playing with the RWJ as I have a new one in the drawer. I hear they work good but do have fit issues and a lot of mods like you encountered Brad.

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## blsnelling (Nov 27, 2015)

I went back out in the garage and came up with a solution. Believe it or not, a 372XP XTorq non-HD filter elbow is a direct fit on the Dolmar filter! I modified the intake boot so that it could be rotated, although I believe you could probably use a 390XP intake boot. Now that the carb sets flat, I was able to rotate the choke arm back down as it's supposed to be, and then bend the choke rod to fit. The choke now works as it should; pull to choke and push to run. This means that I cannot run the Dolmar HD filter, but I had to maintain the HD plastics with the hydrographics. I accomplished this by cutting out the center of the base and the front of the cover. Everything now fits and aligns as a factory saw. I'm very pleased with the results now. I didn't like giving up the HD filter, but proper functionality was more important to me.

Dolmar elbow on the left, Husky on the right. No, it doesn't push into the grommet in the air box, but it does rest on the legs. I don't see this being an issue at all. Also, I had to use 372XTorq carb bolts to reach through the longer adapter bosses. I robbed them from my 372, so an order will have to be made to put my saw back together, lol.






Identical





Dolmar filter on Husky elbow.





Here's the custom choke rod. It has been bent and shortened.










Run position





Choke position















Filter base altered.










Cover altered.


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## blsnelling (Nov 27, 2015)

Here's the final look with the black handle, cylinder, muffler, dawgs, and bar nuts.


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## MillerModSaws (Nov 27, 2015)

Very nice!


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## bryanr2 (Nov 27, 2015)

blsnelling said:


> Here's the final look with the black handle, cylinder, muffler, dawgs, and bar nuts.


that's got to be one of the most "tricked out" saws on AS. Looks really good.


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## Poleman (Nov 27, 2015)

VERY GOOD WORK BRAD!!!!!! GREAT pictures to go along with it. 

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## blsnelling (Nov 27, 2015)

mdavlee said:


> I didn't have near as many mods to get that carb to work. I took the choke out anyway. I can squirt a shot of fuel in and run it.


The choke was the main driver of these mods.


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## Paragon Builder (Nov 27, 2015)

Very nice work Brad!


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## SCHallenger (Nov 28, 2015)

If there was a "runway" for "hot looking" saws, that one would take the blue ribbon!!!


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## blsnelling (Jan 18, 2016)

After 4 months, this saw is finally done and headed home. I went round and round with the hydrographics guy trying to get it right. I'm glad I did. It looks fantastic!


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## blsnelling (Jan 18, 2016)

Here's the final video I made with it.


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## Edwad (Jan 18, 2016)

blsnelling said:


> Here's the final video I made with it.



Thanks Brad! Excellent job as always!!


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## wde_1978 (Jan 19, 2016)

blsnelling said:


> Here's the final video I made with it.



Meh, too slow!
That Stihl bar is stealing too much UMPH.
That sweet saw would perform better with a Dolmar bar! 

She's a head turner no doubt!


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## CoreyB (Jan 19, 2016)

Very nice. That tricked out saw just needs a bar to match. A sugihara or total would look real good on her.


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## blsnelling (Jan 19, 2016)

Not ideal weight wise, but a Cannon would look sweet on there, since they're black with orange letters.


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## bikemike (Jan 19, 2016)

blsnelling said:


> I would love to try a modded carb, just don't want to take a chance messing up what's already running great, and not mine.


Send me a proven working carb. Before.
after


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