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Piston clearance


Brad Franken

Had my 2 1/4 United running for about 30 min. I think maybe it needs a bit more piston clearance. With a 4" bore what do you think the max piston Dia. should be? I had a new sleeve installed & it measures exactly 4" The piston is 3.994 Thanks Brad

Kevin A. Behnke

The clearance should be good for cast iron pistons. I have had in the past, tighting of the piston pin retaining bolt will distort the piston enough to create a tight spot on the piston. If this happens use prussian blue to find the tight spot and file off the high spot.


you should have .003 to.005 clearance.check at the skirt 90 deg from the wrist pin