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Adam842

crank question

4 posts in this topic

Right now I am rebuilding a yz400f that i bought off my buddy for $150. He sold it because he was finding metal shavings in his oil. when i took the top end off I saw the crank has a gouge on the weight just on one side from the rod hitting it at BDC, My question is how could the rod rub the weight if the piston still fits tight in the cylinder. Could it be from last year when he installed a new piston could he of torqued the head down more to one side letting the rod hit the counter weights or what. I don't know if this helps but the top of the piston has tons of carbon and fouled lots of plugs after the piston had about 50hrs on it and the crank stills turns real easily. Any input is appreciated, 

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Right now I am rebuilding a yz400f that i bought off my buddy for $150. He sold it because he was finding metal shavings in his oil. when i took the top end off I saw the crank has a gouge on the weight just on one side from the rod hitting it at BDC, My question is how could the rod rub the weight if the piston still fits tight in the cylinder. Could it be from last year when he installed a new piston could he of torqued the head down more to one side letting the rod hit the counter weights or what. I don't know if this helps but the top of the piston has tons of carbon and fouled lots of plugs after the piston had about 50hrs on it and the crank stills turns real easily. Any input is appreciated, 

 

Can you post a pic?

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the crank has a gouge on the weight just on one side from the rod hitting it at BDC, My question is how could the rod rub the weight if the piston still fits tight in the cylinder.

 

The piston doesn't center the rod, the rod side shims do.  Side clearance of the rod on the crank pin shouldn't exceed .020"

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