I just bought a used Enya .46-4C and it clicks also. I have completely diassembled and cleaned the engine. Mine clicks twice each time the toe of the cam lobe raises the tappet and loweres the tappet. I think my situation is attributable to sloppy gear teeth lash in the cam drive mechanisim. I suspect that when the engine is running that the momentum of the moving parts will keep everything tight. I haven't run my engine yet.

Anyone out there know for sure.

Bill