DO NOT RUN THE MOTOR LIKE THIS!

I think I know what happened.

I'd bet the guy who o-ringed the head took off the original head gasket then o-ringed the head and stuck it back on without checking anything much less cutting the squish, dome, adjusting the deck height.

Take it to Jerry he should be able to fix it pretty easy.

It might be faster and cheaper to just bring him the head, jug, & piston but check with him first.