Jun 30, 2003
Hi, I've got a 2000 kx100 motor I've torn down on a bike I bought with a damaged motor. The clutch side main bearing was out. During re-assembly I noticed that the crank counterweight on that side runs extremely close to crankcase, it actually was rubbing until I gave the drive end of the crank a couple of blows with a plastic mallet to move the crank over in the bearings slightly to gain some clearance but it is still much tighter than the other side. How much side clearance is typical for an engine. I'm wondering if this may be why the main bearing failed in the first place due to insufficient oil mixture getting to it. I've got .020" side play at the rod bearing so I'm thinking I could squeeze another .010" clearance by pressing the crank together slightly. Does this sound right? Also should the crank be shimmed so the crank is tight between the main bearing inner races or is there usually some clearance. I wouldn't think over time that the crank would "walk" in the bearing to where it would rub the case but I'd also hate to have that happen.

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