How does one change the timeing?

what timing? ignition timing? intake timing? exhaust timing?

to change (you can usually only RAISE, not LOWER) intake timing, you can either A. trim the amount needed off the skirt of the piston or B. grind the bottom of the intake port the amount needed to bring the timing to where you want. To change the exhaust timing, you grind on the roof (top) of the exhaust port the amount needed to bring the timing to where you want.

Thank you .Don