I have a friend that is going to restore a shorthood and is trying to decide if he should rebuild the engine. The machine was supposedly completely rebuilt sometime before he bought it. He checked compression and it had about 89 on each cylinder. Is this too low to leave engine alone and restore the rest or should he go through the engine?
Reply:I would start the machine and if possible run it under full load and get it warmed up to full temp. Then recheck the compression by cranking with a fully charged battery and with the throttle in the wide open posistion. If the engine does not crank fast enough you will not get an accurate reading on your gauge. Make up an adapter to thread into the spark plug holes with aa air coupler on the other end. Turn the engine over to locate tdc on #1 cyl. screw your adapter into #1 cyl and apply shop air at about 100 to 125 psi. If you hear air leaking out the exhaust- bad exhayst valve; air leaking from carb- bad intake valve; air leaking into base- bad rings. Check each cylinder in the same way. this should give you a fairly accurate assement of the condition of the engine.
Reply:Thanks for the info. I never thought about testing valves like that. Very good idea.
发表于 2021-8-31 23:36:28