I recently did the NyRoc muffler mod to my 04 p700. Before it would do 69 mph, now it only does 57 mph. It also won't idle very long and when you let off of the gas abruptly it back fires.


Today it also tripped the check belt light but after removing the cover I found it not to be tripped after all. Had to reset it and will wait and see if it does it again. I tried to check belt deflection but had no way of knowing if my belt was riding as high as it could. Iwould turn the back pully but the belt wouldn't change height.

 

Not to sure about cluth problem.But it sounds to me like your jetting is off..Try going up a size on the main jets...

 

Sounds like its too lean,(loss of power and backfiring), hows the air filter? it will probably need to be jetted up. check the spark plug for color.