Small Engine Troubleshooting Problems? Ask a Mechanic Now.
You did'nt check the valve clearances when you had the head off? The valves are not adjustable without grinding off the tips. Clearance needs to be around .006 inch.
Compression is a result of piston rings and valves seating, and head gasket!
Valve may be sticking and is not fully closing. That would be my thought.
Not that unusual!
did you find the problem?