Good question..I'm not positive but I will get back to you how ever setting the squish is also important, as well as the exhaust timing
Setting the exhaust timing is simple remove you're exhaust pipe from the motor and look into the exhaust port. You should see you're piston pull the pull starter slowly until the top of the piston is as far down as it will go it see be level with the bottom of you're exhaust port.
Setting the squish is also easy simply remove you're spark plug, and take a piece of 10mm Soldering wire(you can buy it at radio shack) and bend it into a small L and stick it inside you're spark pluck port. Now pull the pull starter slowly and the piston will smash the soft wire then remove the wire and measure how thick it is that is you're squish setting.