Be sure the valve clearance has been adjusted before trying a compression test. I've seen a tight valve give a false compression test reading on several occasions. Ditto on the cylinder leakdown check- - - -it will give you a much more accurate idea of what's going on. I use an air pressure regulator to adjust the pressure to 100 PSI with no air flowing, and record the pressure with the air connected to each cylinder. For instance- - - -90 PSI at the cylinder = a 10% leakdown rate. A good cylinder will score somewhere in the mid to high 90s. Air leak at the exhaust port- - - -bad exhaust valve, air at the carburetor, bad intake valve- - - -air at the oil filler, bad piston rings. Bubbles in the radiator- - - - -leaky head gasket or a cracked cylinder head or cylinder wall.
Jerry
