Ive been checking around a different shops about a port & polish job on my 400ex. Several different ones are offering 3 angle valve jobs for a few extra bucks. What does this do to the performance, some please explain. Thanks!

 

Not sure on the 3angle, but porting increases the amount of fuel released into the cylinder, giving you a bigger "explosion" when the spark plug fires. Therefore, it spins your crank faster, and gives youre more speed.

 

If the 400EX is like the Honda utility quads you already have a 3 angle valve job.

 

The three angle job is where they grind 3 distinct angles into the valve surface and the valve seat. This is mainly a reliability feature with created a more reliable seal with the valves.

 

Im currently going to school for this kinda stuff and just last week we started valve grinding and were told basicly what 250rampage said, for durability and good valve seating.