2 stroke exhaust pipe
The two stroke exhaust pipe is a very important tuning tool of a two stroke engine. A stock two cycle engine is usually tuned to make reasonable power across the power band. Aftermarket pipes are called expansion chambers because of the way the pipe expands in the center. A 2 stroke engine has a very strong exhaust pulse that occurs as the piston passes the flat top of the exhaust port. The quick pressure pulse moves quickly down the pipe and creates a shock wave as it exits the end of the pipe. Part of this strong pulse wave travels back up the pipe and if timed correctly bounces off the piston as it travels downward.
