Question on Play in crankshaft ? yz250

Helping a friend with an '01 yz250.

Should there be any play in the crank ? There is no up down play but i can push or pull the crank from side to side about 1/8th to 1/16th of an inch.

A rattling or rumbling noise just started from the bottom end.

The bike runs wells, shifts well, just new noise.

We pulled the right engine cover and can't anything obvious as to where the noise is coming from. Power valve and water pump seem fine. Noise is there in neutral and also when in gear, either with clutch in or out.

any help is appreciated. Thanks

Have you checked the main bearings as well? Take off the left side (flywheel) cover and try and wiggle the flywheel. There should be no movement. If there is, then that is your culprit.

Also, when you are checking the rod for play (up and down) you need to slowly rotate the crank and feel at every point. The lower rod bearing once went bad on my KX250. I pulled the cylinder, checked the rod, and figured that everything was OK. It wasn't. The sound continued, so I pulled the cylinder again. I found that there was only play at one small point in the rotation.

The crankshaft bearings are a tight fit on the crank and and also in the case. If I understand what you are doing is pulling and pushing the crank back and forth horizontally sounds like you have a serious problem going on there.

Ya, pull it apart before it gets UGLY.

chub, just to clarify:

Is the side to side play that you are describing in the rod, or the crankshaft?

Some side to side play is normal in the rod, but there should be no play in the crankshaft.

The play is in the crankshaft. I have not checked the rod as the top end is still on the engine.

If I move either the flywheel or the main gear on the right side of the crank, I can move it slightly from right to left, but doesn't seem to have any up down movement.

the noise was a knock like something was bouncing around, but not a consistant knock. I think it could be the crank shaft bouncing back and forth a little.

So, just to confirm that there should be NO play up down, right left.

Thanks for the replies.

I can move the rod slightly back and forth, but the flywheel will not move.

the crank it self shouldnt more, the rod its self should move a hair side to side but NO up and down play

im starting to get this to. sounds like a bolt bouncing around, its not down on power starts easy tons of compression, going to check it out this week, doesnt make any since only 20hours on it, and using 24:1 oil using castrol 927 so its getting plenty of oil

If its not the bearings, then your crank has worn down from use over time.

Causing the crank to move side to side. It is out of spec!

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