Chainsaw Repair

So, I removed 0.250 from the 4.25 inch long pipe, high revs still @10.5K when it begins to four stroke so it appears that the additional length wasn't doing anything. I have 0.250 of pipe left that I can remove before reaching the design dimensions. I plan to do this in 0.125 increments with the saw actually cutting wood, and see where we are at.

I have done a few muffler mods with pipes and by making slits or making a small box for the outlet.   They all seem to perform the same to me.   
As far as tune pipes are concerned you will never get a box muffler to come close to a tune pipe.   For a tune pipe to work you have to have the correct length, shape and size to take advantage of the harmonic waves that are created at the exhaust.   A box muffler cannot perform this in any way shape or form by just changing the outlet.

The tuned pipe on that 372 is like super charging on a 2 stroke.   I'll bet it made a huge difference.