- Jul 9, 2003
Acctually I have a friend that has a 400EX fourwheeler but as I understand the motors are nearly identical? I was going to do some head mods mainly a poilsh job but maybe port match the intake and exhaust to their respective manifolds and maybe re radius the intake runner. Just wondering if all this (mainly the polishing of the combustion chamber and runners) is worth the time and effort for some gain in flow. I wish that I had a flow bench to verify this but i do not. any other head mods recomended?