How to check Dech Height & Head Clearance?

Take a piece of thin solder (.030 - .035) and bend a small L in the end. Remove the glow plug. Then place the end with the L into the glow put hole. You want the tip of the L to hit the cylinder wall and then turn the engine over. The top of the piston will press the solder into the cylinder head and flatten the solder.

Carefully pull the flatted solder out of the motor. Then measure the thickness for the flattened solder with calipers. To adjust the head clearance, remove the head and button. Now add or remove the appropriate brass shims to get the head clearance you are looking for.

Put the button and head back on, make sure you tighten the screw evenly and double-check the head clearance. I run most of my .12 engines between .017 and .020 and for my .21 engine between .021-.024.

By Adam Drake