3120 muffler mods

[clyde]

My husky 3120 exhaust seems very restricted. If I put some holes in the muffler will it run too lean? Ther is no high speed jetting adjustment. If it is lean can I get the proper jets and install them?

 

[bugfart]

Holy Crap!
What is your goal, to drive your saw to work?
I tried reading up on this series carb... I kept finding myself at sites that sell one man flying craft.

I suppose you could try squeezing in a WB series and start drilling holes in the muffler till you like it. That was a joke; I am only kidding.

Good question about the single adjustment carb. Never even thought about that. They're really trying to keep our fingers out of things these days huh? Love yur attitude.

 

[clyde]

bugfart, milling!
I wouldn't use that monster for anything else....except for holloween with the 6ft bar.

 

[bugfart]

I noticed they have kits for those series of carbs to include an external pump. You know, for when you want to pass or something...

Long ago they messed with gear reduction; maybe its time to consider a tranny. Split axel saws with high gear.

 

[bman]

Cllyde I have a newer 3120 I use for milling. I was concerned about the stress put upon it, it seemed to run lean and even apperared to vapor lock a couple of times after a long cut and rest/restart. I followed the advise of another and drilled the main jet out two numbered drill sizes larger. Have not had another vapor lock. I also removed the inner baffle tube in the muffler and slightly increased the outlet opening using a unibit. Actualy I drilled the opening utill the end of the inner baffle tube weld was gone which allowed the inner baffle tube to be removed. (prior to this I had to reach thru the opening that mates to the exhaust port and saw the other end of the baffle tube free with a hacksaw blade, somewhat time consumer cause you cant get a very long stroke in there) I also pryed the louvered outlet cover slots to a less restrictive postion but left the screen in place. The difference was a somewhat louder saw that would then "four stroke" coming out of the cut like a good saw should. Seat of the pants seemed to suggest it reved quicker. Now as for milling where the saw runs much more heavly loaded I cant say for sure that it felt as if it pulled any better. I have since welded into the muller outlet beneath the screen a short section of tubing to more closely match the stock opening sans the baffle tube. I think I may try a stock muffler again with the rejetted carb in light of the low rev/hi load nature of milling ,but for sure the larger main jet size lets the say run cooler. I can say for sure that the muffler mod seemed to allowed the saw to scavenge a richer mix as the saw would give that "four stroke" tone when reved no load prior to the gov taken over. This is somewhat un scientific but follows a logical approach based on current epa engineering of the newer saws. Hope this helps, bman

 

[Chopwood]

the "four-stroking" you are hearing at no load is the rev limiter kicking in anywhere from 10,200-12,000RPM, depending on the year of the saw. As far as I know, they all came from the factory with a limiter.