My $.02....Remove the plugs, check at the taper seat on the plug for contact marks.... Iron head should give a consistent smear of the black oxide coating at the taper seat.
Inspect the plug hole in the cylinder head (If possible, Mirror would help) for any debris, If you have compressed air blow out area at plug hole . If everything checks out re install the plugs until finger tight, further tighten up to 1/8 turn. Unless you cross threaded one of the plug holes at some time in the past the iron head should hold the thread.
Again just my $.02 unless someone else has a different perspective.
Inspect the plug hole in the cylinder head (If possible, Mirror would help) for any debris, If you have compressed air blow out area at plug hole . If everything checks out re install the plugs until finger tight, further tighten up to 1/8 turn. Unless you cross threaded one of the plug holes at some time in the past the iron head should hold the thread.
Again just my $.02 unless someone else has a different perspective.
