Only if you require the utmost performance the engine is capable of. I run the OEM exhaust with the spark arrester on my machine. I have never had it dyno'ed or rejetted and recently took 3rd place in the 50 year old class of a 3 hour hare scramble race. I was only a minute and 43 seconds out of 2nd place, but I was satisfied and a bit surprised to do that well. I'm 60 years old. Remember, it's not the ability of the machine that's important - it's the ability of the rider
do i need to dyno and rejet my 400ex if i take the spark rester out of my exhaust cap
Linear Mode
