Originally Posted by ziggy12345
Hi
For 25% Notro you need a head clarance of around 0.4-0.5mm. Measure the head clearance by inserting a length of solder into the glow plug hole and turning the piston over so it crimps the solder on the head. Measire the flat spot.
Maybe for a .12cc engine 0.4- 0.5mm would be OK, but for a .21 you need about 0.7mm of clearance. 0.4- 0.5mm is far to little here in the states for a .21 and beyond most anyones margin of comfort for clearance at RPM issues. Remember.... the rod is stretching under racing conditions.