You can time it with out taking the head off. You need a dial indicator that has a remove-able contact point on it. Thread off the contact point and put a piece of stiff wire on it, bend the end of the wire into an L shape so it can reach in through the plug hole and touch the piston, mount the indicator to the motor. Do as described above checking the close - open position relative to the max piston upward travel subtract the amount of travel for the correct timing event. I checked mine this way - no issues.