I recently bought a used craftsman mower, and the engine has a knock. I discovered a new problem, which is that the fuel shut off solenoid is faulty and was causing gas to mix with the oil. I have ordered a new solenoid, but I was wondering if that also could have something to do with the knocking sound? I was thinking maybe there could have been too much pressure on the crankcase, but I’m not exactly sure what all causes knocking. Let me know what you think! (I checked to make sure that all the engine mount bolts were tight, so that’s not the cause)
The fuel solenoid has nothing to do with gas in the oil. That is caused by a bad float needle and seat. Time to clean and rebuild the carb. Yes, gas in the oil can contribute to knocking. Don’t forget to change the oil before running again.
#4
StarTech
Or if it has a Nikki carburetor which many do it would more like be the fuel bowl gasket and o-ring on the fuel transfer tube. IF it still knocks after repairing the carburetor and oil change then it has been ran too long and aluminum from the rod is already transfering to crankshaft journal and the rod will soon break and put a hole through the crankcase.
Or perhaps more likely, the counter balance bushing is shot. Fatal if that is the case.
Walt Conner
#6
Hammermechanicman
That knock is the new and improved audible tachometer.
If it was run long with the gas oil mix the rod is ,like Star said, toast. At the least you will need new rods and hope the crank will clean up and polish out if you know what to do. If the crank is scored engine probably not worth trying to fix.
This a single cylinder engine and as I said, the counter balance is more likely, very unusual for the rod to knock, usually they just throw under those circumstances, not knock.
Walt Conner
Whether it is a counterbalance or rod and crankshaft problem, the OP must solve the fuel in oil problem. This can be done at the lowest cost. After that he will have to decide how to proceed.
