Section 9Lubrication and MaintenanceChecking CompressionTo check the cylinder compression, remove all four spark plugs. Then install a compression testing gauge in one of the spark plug holes. Crank the engine with the starter for a few moments while the accelerator is pressed to the floor or while the throttle valve on the carburetor is held wide open. Note the reading and repeat the procedure with the other cylinders. Compression pressures for the various engines covered by this manual are listed in ENGINE AND CLUTCH, Tolerances, Wear Limits, and Settings. If the pressure is below 100 psi (7 kg/cm2) on 1968 through 1971 models or below 71 psi (5 kg/cm2) on 1972 and later models, the valves may need to be ground, piston rings replaced, or new cylinders and pistons installed. LUBRICATION AND MAINTENANCE | 
