The straight scoop on backpressure

[Pitch Black]

i posted about my 3" exhaust over on the jet and someone told me to read this. its really cool and nice to know.
http://www.dsmtuners.com/forums/showthr ... scavenging

[Louis Zerr]

I think a major misconception comes from the fact that 2 stroke engines require backpressure due to the way they work. Since the exhaust stroke and intake stroke are the same no backpressure would result in all the air/fuel/oil mixture going out the exhaust. Many fathers have passed along this information as relating to both 2 stroke and 4 stroke engines.
http://science.howstuffworks.com/two-stroke.htm