Aftermarket head pipe question

[smokey480]

I am ordering a new HMF slip on and would like to know how much of a difference the aftermarket head pipe adds to the performance. Im not ready to spend the money right now and buy the whole thing and would like to know how much the head pipe will add. Also if I add it later will I need to rejet again. BTW this is for a 2005 400ex.. thanks

[A A R O N]

An aftermarket head pipe is NOT worth the extra money unless you're VERY serious into racing. The actual tail pipe is where most of the restriction of the stock exhaust lies. The money would be better spent on handling improvements in your case with the 400ex. The HMF is a nice pipe and the slip-on is more than sufficient.