ive been thinking, is there a rev limiter or governer on the 99 trailboss 250??? if so were at? thanks for the help!!!!

 

polarisr,

No, the pipe limits the RPMs of the machine. If you switch to a different pipe (i.e. top end pipe), the machine will rev to a higher RPM.

The exhaust pipe on a two stroke acts like a sort of valve. When the engine reaches a certain RPM, a pressure wave develops in the pipe. This pressure wave helps keep the fuel/air mix in the cylinder where it would do the most good. When there isn't a pressure wave in the pipe, it causes a condition where the fuel/air mixture partly leaves the cylinder also known as known as scavenging. When the fuel/air mixture is kept in the cylinder, you will notice that it has a whole lot more power. This is refered to as "coming on the pipe".

If you look at a two stroke pipe, you'll notice that it is bigger where the exhaust comes out of the motor than where the exhaust exits the pipe. Pipe builders can vary the size and shape of the expansion chamber (the big part of the pipe) to suit various riding needs. Most, if not all of the stock Polaris pipes are made for low end power as they have small expansion chambers. They make their power in the lower RPM range to make it easier for beginners. By adding an aftermarket pipe (one with a visibly larger expansion chamber), it will take more RPMs for the pressure wave to develop. How many RPMs it will take is determined by the size of the expansion chamber. Basically the bigger and longer the expansion chamber is the more RPMs will be required for the machine to "come on the pipe".

Hope this helps!

 

THANK YOU!!!!!!!!! i learned something new, i am getting my pipe ordered so it will bring the rpm's up. you seem to know a lot about this!! thanks a lot though.