Take off the heads and scrape off the carbon and see if the
noise goes away.

Fish

Take off the heads and scrape off the carbon and see if the
noise goes away.

Fish

Do what Fish says first,the connecting rod has no bearing,matal against metal with a thin film of oil seperating the two pieces of metal(welcome to small engines)...Jim

I have owned an opposed twin on an old Gilson for about 20 years and it has a knocking sound when idling with no load. The knock disappears when the blades are engaged at idle. The knock cannot be detected at high speed - load or no load. I believe this is a characteristic of the vertical opposed twins with splash lubrication. They seem to run forever.

Opposed twins with full pressure lubrication are as smooth and quiet as any engine out there - no knock.

the question is - Are you describing the characteristic knock - or do you have something more serious. As mentioned, cleaning the head carbon is a good idea and it is easy to clean. Change the oil to SAE 30. Make sure the oil level is maintained in the operating range. Make sure the dip stick is screwed down and not simply rested on the dip stick housing.

If your engine does have a serious problem, there are many good engines remaining on expired equipment. Cooling fins must be kept clean to reduce the possibility of a valve seat failure. A Murray mower is not worth the expense of a new short block - even if you can find one.

Thanks Gentlemen, for your replies. I'm encouraged to take my first small engine apart, if the owner of this tractor doesn't claim it soon. Will post again if I do.

Can't thank you enough for your help,
PlumDucky