My friend recently put a glass pack muffler for a car on his four wheeler..one for a car the big *** red ones...its alot louder now but is about 7 mph slower but he says it takes off alot faster...what were wondering is...will it hurt his machine?

 

Well let's put it this way, he's not helping it and anyone who sees him is probably laughing their a$$ off at what a redneck bum he is. I have seen the same thing done on a raptor 660, it made less power than just removing the spark arrestor even when rejetting it. I'll bet the guy didnt do that either, which could lean him out and burn up the engine.

 

if he didn't rejet it then he's definitely running lean. That'll do damage to the motor, and if it decreased the back pressure enough he might have burn up valves too. not a good idea.