parts bike

[2bhappy]

Nobody mentioned the possibility of a connecting rod bearing seizing or spinning. Could this be the problem?

Marc

[randy]

Yes, Marc. I believe I did.

To answer your question Dean;


Crank or rod bearings are made of soft materials, usually tin and copper. They are held in place by keyways in the bearing caps. the bearings have corresonding flanges that fit into the keyways. This is what keeps them from spinning in their bores.

When starved for oil, the tin layer of the bearing will wipe off first, then the copper. If they heat up enough, the motor will sieze. At the moment of siezure, the bearing flange fails and the bearing spins 'cause it's welded to the rotating part (crank).

This is known as a 'spun bearing'. It's all bad.


Other than the main and rod bearings, I am not aware of any other parts in the crankcase that contain copper (guys chime in here). the cams don't have bearing shells.

The only way to know for sure that this is your problem is to split the cases to get to the bearings.

Then again, this is only a parts bike, right?