They aren't the typical huge expansion chambers that you see on practicly every two stroke. they almost look like four stroke pipes. on my sister's trailboss it gets a little bit bigger in the middle but it is nothing compared to my blaster's pipe. can someone give me an explanation?

 

Just go get an aftermarket unit and you'll see huge! [img]i/expressions/face-icon-small-happy.gif[/img]

 

They have to fit under the bodywork (and between the frame and radiator on the 400). There are a lot of different shaped expansion chambers that will accomplish similar results. You have to remember that these come from the factory with rather mild tuning. There's lots of room for improvement with aftermarket stuff. That doesn't mean there is anything wrong with factory pipe, it just has to juggle several different considerations. Like most stuff built to appeal to the masses, it's a compromise.

 

And to add, the RPM's on stock Polaris 2-strokes are only about 5750 give or take a bit. That is not many if you compare that to a 250R or Banshee turning 9000. So the requirements for an expansion chamber would be less. Size of the chamber, location, stinger tip size, and several other variables are involved in manufacturing. That's why you pay for the R&D. And like Ken said, look at a race pipe and you'll see the difference for sure. But they also turn over 7000 RPMs.[img]i/expressions/face-icon-small-happy.gif[/img]