I purchased the round high compression cylinder head from JNMotors. My piston to deck dimension was 0.100" so I had 0.080" machined off. I didn't take the recommended 0.090" off to get to a clearance of 0.010" just to be on the safe side. I'm using an E3.12 spark plug with a reach length from the bottom of the washer to the tip of the electrode of 0.475".
When I started the engine it made a lot of metal to metal banging sound. I guessed is was piston to plug but the plug and piston didn't show any impact points.
I added a second stock head gasket which is 0.030" thick and the sound went away.
Anybody try this head with the recommended machining to the jug and get similar results? My engine is a 66cc, 2 cycle Grubee purchased new in 2012.
Engine has a lot more compression and more power. Added about 3mph to top end. I have a shift kit and getting the motor started requires a lot of effort. I weigh about 200lbs and it's all I can do to get the engine to crank. Small price to pay for 3mph.
When I started the engine it made a lot of metal to metal banging sound. I guessed is was piston to plug but the plug and piston didn't show any impact points.
I added a second stock head gasket which is 0.030" thick and the sound went away.
Anybody try this head with the recommended machining to the jug and get similar results? My engine is a 66cc, 2 cycle Grubee purchased new in 2012.
Engine has a lot more compression and more power. Added about 3mph to top end. I have a shift kit and getting the motor started requires a lot of effort. I weigh about 200lbs and it's all I can do to get the engine to crank. Small price to pay for 3mph.
