I doubt that it is the coil box. The way that this engine is kept from RPM's is in the port, carb and spark advance, and that comes out of the rotor. Also the muffler is restricted to keep the noise down and limit the HP. To my knowledge no one has come up with a High output coil, and no one has been able to tell if the coil box has the ability to advance the ignition! I don't have any engines that are not ported or that have as stock carb, and that is how I get my engines to run well. Have fun, Dave
Does anybody know if the coil C.D.I or whatever it is the little black box that the spark plug wire comes out of is worth up grading? Still can't get the rpms I want.