Hello all, first time poster. Awhile back I decided to rebuild a mower that had “slop” in the piston ring when connected to the crankshaft. I was successful in getting it to run [ran like new!] but the spark plug blew out of the cylinder head because the threads were stripped from installing and uninstalling the spark plug. Instead of retapping the threads I went a cheaper route and bought a used cylinder head. I installed the cylinder head with new gasket and now the mower won’t start. I’m using a new spark plug. Rechecked the ignition coil on the flywheel with a feeler gauge. Also checked the ignition coil with my multimeter and got a reading of 5000 ohms. Any help would be appreciated.