Trimming the piston actually goes hand in hand with porting. It is an area that you really need to be exact on. If you take too much off or open the ports too much the bike will run bad and actually lose power. I wouldnt recommend doing it yourself unless you can get exact numbers and the exacxt place to remove the material from. You may want to try macdizzy's site. they have alot of tuners and porting gurus there that can help you out. I think it is macdizzy.com. But you gotta hurry, they are gonna be a pay site starting jan.

 

Ha go to macdizzy site to see alot of fake pictures...

 

say bubba what would happen if you only widened out the exhaust port

 

the holes in the intake skirt are most likely for short circuiting the transfer ports so the A/F charge can bypass the normal circuit it makes around the crank
allows the pipe to scavenge alot more fresh intake mixture
I went from a stock 5/16 hole in my yamaha 600 mountain max to 1/2 and noticed a big difference no other mods and I grabbed 400 RPM