effects of removing baffle/converter from stock pipe?

B

bigbutterbean

Active Member
i have a grubee 2 stroke engine with a pull start and centrifugal clutch. I modified the stock pipe. here is what I did: I cut the pipe open and removed as much of the baffling as i could and drilled the rest of the way through the honeycomb. I then welded another piece of pipe on and welded the cap back on. the pipe is almost the exact same size as it was before. the difference is that the exhaust flows straight through the pipe and has no baffling to go through. It still has a cap on the end and so still acts as an expansion chamber. I dont notice any difference in back pressure, but i could be wrong. i dont notice any difference in power either. my question is, are there any potential long term damaging effects that could be caused by modifying the muffler in this way? sorry for the long post.
 
some people say these engines need good back-pressure or you can harm them.

i don't believe that.

on 2 of my bikes i've completely gutted the stock pipe and put a Supertrapp disc muffler on the end. there's still an end cap, but not much in the way of back-pressure.

both bikes run great, and one of them has over a year on the engine, the other a few months.

the only real disadvantage i can see (hear) is it's louder.
 
actually, they do need back pressure. without enough back pressure, the timing goes wrong and the engine will have serious power reductions. if you havent noticed any power loss in a year, then you still have back pressure. so do i. my main question though is referring to heat. does the engine run hotter with the catalytic converter out? i previously used this modified muffler on my last engine. after a year of moderately heavy use, the piston rings burned out. was it from heavy use, or did it get too hot because the muffler was gutted?
 
The engine should run cooler with less exhaust restriction. You may need to re-adjust the carb so you aren't running too lean. You may see a marginal power increase, and a very slight gain in rpm.
 
I am on my 2nd muffler (thanks ZoomBicycles for actually honoring the warranty), my bike had MUCH more power when I removed the end cap and canister. It ran great, but was too damn loud. On the new muffler, I ran it with the endcap and can off, but still too loud. So I took two pairs of vice grips and just bent the two metal disks up out of the way, and replaced the can and endcap. The power is marginally reduced, as well as the sound. Got to make a sacrifice I guess. Power or noise...
 
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