Re: Exsoust
The back pressure thing is kind of a myth...
If you take off the exhaust and don't change anything else, you can cause problems.
However, I ran a McCullogh go kart for two years much to the neighbors dismay with absolutely no exhaust and it never had a problem. (I was an ignorant 13 year old, we bought the kart that way, and didn't know any better).
Guys have run control line model airplanes engines from the 30's until the 70's with no issues. They only started using mufflers so they could continue to fly at the local parks.
If you remove a two stroke exhaust, you will need to make the carb settings considerable richer, and the off throttle performance may suffer.
Having said all that, DON'T DO IT TO YOUR MOTORIZED BICYCLE for the reasons stated by 2Door.