Thursday, June 30, 2016

Chainsaw Muffler Mod

Let's face it folks, current chainsaws are built for EPA emissions requirements, not speed and power. These days, they're so choked off that you wonder if they really produce the horsepower advertised on the box.

If you feel that your saw is lagging, which you will, you should first consider modding the muffler. Caution: You may want to wait until the warranty goes bye bye before you try any chainsaw muffler mods.

The whole idea is to reduce exhaust restriction. The first things you should try are:
  • Port the existing outlet to make it bigger.
  • Remove baffles, if your chainsaw muffler has any.

Why Chainsaw Mods?

If you were running your body under a fast and rigorous work load and taking quick deep breaths but only exhaling very slowly, how long would you go at peak performance? Not long. Similarly, you should let a saw breathe a little, like it needs to.

Two cycle engines do not use the piston to push out the exhaust, so any restriction in the exhaust stream will take away from their performance. Modifying the chainsaw muffler will allow your saw to run cooler, and probably give an extra 1/2 HP. A byproduct of a chainsaw muffler mod is that it will enable the saw to run cooler, and that will increase its life.

When it comes to chainsaw mods, you should consider muffler mods first because they are easy, and they will effectively increase your saw's horsepower with very little expense. In fact, if you have a drill and a grinder, you can do very effective chainsaw mods in 15 minutes or so.

After, or Along With a Chainsaw Muffler Mod

When you modify a chainsaw muffler to increase the flow of exhaust, you also have to adjust the carburetor to avoid running too lean. That'll take you another 15 minutes or so. You're going to have to tweak the carburetor after porting a chainsaw muffler. You may even want to tune the carb a couple of times after a muffler mod. Probably won't gain much power until you turn the fuel up anyway. You'll have to adjust your saw's carb a little bit richer on the High speed screw.

How To Mod a Chainsaw Muffler

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Modifying the muffler can mean opening a larger port on the outlet of adding another port. Power will increase as will the noise level. Do not go by noise level increase alone. Noisier does not mean better, faster, more powerful.

When you modify a muffler, you want to get the max rpm. After you port it, you'll notice that the point where the saw can 4 stroke has changed. By “4 stroke” I mean the gurgle sound at WOT. By WOT, I mean wide open throttle.

Make sure you adjust the high speed needle on your carb a little richer than the original setting was, so that you don't burn up your engine. Nobody wants to buy a new saw sooner than they have to. Take the muffler off the saw before you try it. Blow it off good with air before putting it back on. Any metal filings or grinding dust that gets in the cylinder can do some real damage to the piston and cylinder.

The first thing you want to do in a muffler mod is to port match the muffler, gasket, and cylinder. This means that you inspect the individual components to ensure there is no overlap of material into the exhaust port of the cylinder.

How Much Can You Port a Muffler?

The amount that you can open the muffler depends upon the size of the exhaust port on the barrel and the amount of transfer port area internally. A good place to start is an opening equal to the cylinder exhaust port. With some experimentation, you can work up to 1.5x the area of the cylinder exhaust port.

You need at least a little bit of back pressure in the exhaust system to keep your saw running to its full potential. Too big a hole, or no muffler at all, will suck. Sometimes, even 1.25+ times the exhaust port can be too large. That's why it's best to make a smaller opening at first, then increase the size of the opening if you dare.

If the muffler port is too big, it will actually slow the saw down.

If you screw it up, get your replacement chainsaw muffler at HLSupply.

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