HELP ! Engine Bearing Questions

1. What are the standard size for piston bearings..?..I do not think any work has ever been done on this tractor, the main bearings were measured to be standard according to the parts store (.090 if I remember correctly).

2. What type of clearance should there be between the bearing and crankshaft ? .010-.012 seems extremely excessive, especially when I can rattle it back and fourth on the crankshaft. I think this is the culprit of my knocking.

Any answers or other comments will be greatly appreciated. Thanks !

I checked the piston bearings, and they are the same size as those that were taken out before my rebuild (.062).

Why would it knock after my rebuild rather than before with the same size piston bearings ?

Is it possible that the engine was so tired and my compression so low that it couldn't build up the power to make it knock ?

The crankshaft should measure 2.100" for the rod journals and 2.250" for the main journals. Useally the bearing clearance is .001"-.002". You can not just measure the thickness of the bearing insert, you need to wash and dry off the bearing inserts and connecting rod. Then install the inserts and torque them down to spec. This can also be done with plastic gauge on the crank if it is washed and dried also. You might check the the mains while your at it.

Good Luck,
Kevin (WA)