Beer Belly
Minister of Fire
I'm running a 20 inch on my Farmboss.....it'll cut, but if you bury the bar in a round, you'll see it struggle a little, but it will get the job done
Stihl 029 bar
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My cutting buddy uses and 029 Super with a 20" .325 setup. I modded the muffler for him and it does pretty well.
clemsonfor
Minister of Fire
no matter what it will be slow with the nose buried in oak. My 390 is slow to me fully buried running 3/8 .050 chain. If you downsize to .325 picco chain like Hittin suggests it will speed up a bit with a more narrow kerf. But when I run my smaller 45cc husky saw I realize how fast the 390 was
Not if you stay away from that center rectangle with the drill/dremel. As soon as you start poking holes in that, you have a straight through path for exhaust and noise to get out.
Make your 029/029S/039/MS290, 310, 390 Muffler look like that one and you should see a very noticeable increase in power (after you re-tune the carb of course) without waking the dead. The MS390 I did like that is hardly noticeable from stock, noise wise, but has a definite attitude adjustment in the wood.
Don't forget to open up the deflector cover a bit otherwise it becomes the bottleneck.
You can do it to just about any saw but the amount of work involved and the potential gains to be had vary by model. I have not tried it with a MS250.... yet.
clemsonfor
Minister of Fire
Cool you used my pic Unless the one u did was similarly rusted and dirty as mine? I don't care one bit and feel honored that it looks OK enough for u to use in your excellent directions!
Unless the one u did was similarly rusted and dirty as mine? I don't care one bit and feel honored that it looks OK enough for u to use in your excellent directions!Cool you used my pic
Where do I send the check?
It's exactly the same as the one I did. Unfortunately I do not have pictures of the actual saw I modified. So I stole yours.
He stole it and I printed it out.Cool you used my pic
My buddy rides a Harley.......so I drilled a hole through the rectangle and the deflector. Its loud and flows very well
no matter what it will be slow with the nose buried in oak. My 390 is slow to me fully buried running 3/8 .050 chain. If you downsize to .325 picco chain like Hittin suggests it will speed up a bit with a more narrow kerf. But when I run my smaller 45cc husky saw I realize how fast the 390 was
Corrections: .325 is not picco chain. Picco is 3/8 low profile. Picco bars are extremely hard to find in large format size for Stihl saws (1127 saws are large format). Also .325 does not have any narrower kerf than 3/8 std. unless you go to an aftermarket Stihl size NK .325 B&C. The difference is .325 has a slightly lower profile, and more cutters per length than 3/8 std. I have run many tests of 3/8 vs. .325 on my 026s and 310s, and they were a dead heat. Neither was faster or cut any better. NK has a 10% narrower kerf, but most I have read that have run it say it is not that much better, if at all. I run all 3/8 std. for one size B&C for all my saws, 026 and up.
If you go with the 6 ports on the muffler like you have there, the deflector is still going to limit the flow. I have drilled out the entire outer section with a large slot at the top and an 'L' at the bottom and compared it to a 4 slot port mufflers and they ran pretty much the same. So I stick with the 4 slot ports more or less like you have in your photos, and that is more area than the deflector has with the bevel section ground off. On a 290 that will give you a 4.0-4.1 HP, the original design power for those saws, and the same as a stock 310 (though they are not as smooth as the 310). You can get the same gains from a 310 mod and get stock 390 power, and make a 390 into a poor man's 361. Though the lower rev limit of the 390 keeps them slower than the 361 in timed cuts even with the 'factory' muffler mod; I have tested them back to back with the same B&C and the same logs. Also the 361 is far smoother than any 390, or even a 310.
I fully agree with staying away from porting the dimple section though. I have cut out the entire dimpled section and left the deflector off and they are as loud as hot saws. More power, but the gas mileage drops and you can smell the unburned gas pouring out of them from lack of back pressure. Which is another reason I keep the muffler porting tightened up a tad. Also the max RPM get hit pretty fast with excessive muffler porting, especially with the low rev limit of the 029/290.
These mods are so easy and take 30 minutes if you have done them before. They also make the saw run better and cooler, and they will actually last longer. But as I have said before, they are a modification from factory and EPA standard, and if you take a modified saw into a dealer with these mods, they are required by law to restore them to factory condition, meaning re-installing new original restricted muffler and limiter tabs and de-tuning. It is not illegal for you to do these mods, but it is illegal for them to do these mods, or leave saws as they are if they come across a saw with these modifications.
BTW: here is a good page at Madsen's on carb tuning:
(broken link removed to http://www.madsens1.com/saw_carb_tune.htm)
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