Custom Stihl MS 290 310 390 Ported Chainsaw Muffler 029

The modern saws are great saws, but like all modern saws their muffler does not allow them to show their full potential.  Chainsaw manufacturers are being forced to lower emissions by constricting saws using insufficient muffler port area, and lean carburetor tuning. You paid for a saw that’s capable of much more.

To cure this I have added a .525" port to this muffler with a t304 stainless steel replaceable spark screen. This will allow your saw to scavenge the exhaust gasses more efficiently, allowing more cooling, lubricating fuel/air mixture to be drawn in. Your saw will have more power, will last longer, and will gain a deep satisfying exhaust note.

A few things to consider when fabricating or adding a ported muffler:

Pay attention to how the hot gasses exit the muffler. My mufflers aim the exhaust away from the log and from the operator. Bark will burn if directly exposed to the saw’s exhaust for too long. It's not a pleasant experience breathing the dust, dirt, and exhaust fumes that are bouncing off the log and into your face from muffler ports that are aimed at the log.

The muffler port needs to be sized correctly. If it’s too small the gains are minimal. If its too large you start to loose some of the fresh fuel charge out of the muffler, wasting fuel increasing emissions, and killing efficiency. There is a happy medium here, and I have settled on a design that chainsaw engines run very well with. I have done extensive research in muffler design, and have based my modifications on the relationship of the area of the exhaust port to the area of spark screen and muffler port. This is not an exact science, there is a limited range of port sizes that will work well, as each saw varies with respect to wear, tuning, temperature, altitude, even how much fuel is in the tank.

How much power do I gain? This is by far the biggest bang for the buck modification when it comes to chainsaws. I‘ve never run one of my saws on a chainsaw dynamometer, but I have done some timing tests and the saws are at least 20% faster through the wood. Sometimes bigger gains are found especially when replacing the new crop of catalytic mufflers.

My mufflers are guaranteed. If you don’t like how it looks or performs when you receive it, mail it back to me and I will refund your money.

Your carburetor will probably need to be adjusted after installing this muffler. Failure to do so may result in damage to your saw. If you haven't adjusted your saws carburetor before, please see the following website for instructions on tuning.

http://web.archive.org/web/20051018212959/www.madsens1.com/sawtune.htm

I will paint this muffler high heat black if the winning bidder desires.

I only want satisfied customers.  So please ask any questions you have.

Ships anywhere in the lower 48 states for free.

You can get there from this link...

ScottWojo Modified Chainsaw Mufflers

  There is a great deal of information on tuning saws and lots of very smart and helpful

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