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Crank Inspection

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Hi everyone,

Im in the process of tearing down the engine on my 1998 cr250. I have the jug off and all of the gears off on the right side of the engine (clutch, Kickstarter, etc..) When I rotate the crank it seems to want to settle in several different places. It still rotates smooth and freely, just has a couple spots where it feels like the weights are at the bottom. My thinking was that the crank should only want to settle with the piston at top dead center, not at several other spots in the rotation. Is this normal? Any input would be appreciated, thanks.

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Few things. Was the engine running before you Disassembled it. And if so why are you disassembling it?

To inspect the crank correctly there should be no up-and-down movement of the connecting rod,  Going by the service manual side by side play  Service limit is 0.9mm, However in saying that mine is At 1.0mm Has been for the last five years.

why are you thinking that the crank should settle at top dead centre? doesn’t make any sense. If you don’t have a service manual get yourself one and read up.

Edited by CRJohnny

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1 hour ago, CRJohnny said:

Few things. Was the engine running before you Disassembled it. And if so why are you disassembling it?

To inspect the crank correctly there should be no up-and-down movement of the connecting rod,  Going by the service manual side by side play  Service limit is 0.9mm, However in saying that mine is At 1.0mm Has been for the last five years.

why are you thinking that the crank should settle at top dead centre? doesn’t make any sense. If you don’t have a service manual get yourself one and read up.

I parked it after riding for a while and when I went to start it a couple hours later the kickstart wouldnt go all the way down and it felt like the bike had too much compression. I tried bump starting it and that didn’t work either so I started tearing into it. I put a new top end in it and that didn’t fix the problem so now I’m looking into the bottom end. The only reason I was thinking it would settle at tdc is because of where the weights are positioned on the crank. There’s no up and down rod play and the side to side is very little.

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2 minutes ago, Motox367 said:

Its the magnet on flywheel that you feel 

Thanks, you’re right. Just pulled the flywheel off and it turns over smooth. Any ideas on what else could be wrong with it?

 

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How did the old piston look? Any debris in the bottom of the case? How are the crank bearings? You’re so close you might as well split the cases and rebuild the bottom end. 

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On 9/29/2019 at 7:35 PM, Jack Palmbos said:

Thanks, you’re right. Just pulled the flywheel off and it turns over smooth. Any ideas on what else could be wrong with it?

 

I would be looking at why it was rough turning over with the FW on and not with it off. Sounds like you need to split the cases and have the crank checked for straightness. Especially if you installed a new piston kit and it still won't run. My money is on the crank is bad.

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5 minutes ago, FPMXer said:

I would be looking at why it was rough turning over with the FW on and not with it off. Sounds like you need to split the cases and have the crank checked for straightness. Especially if you installed a new piston kit and it still won't run. My money is on the crank is bad.

You can spin crank while in and see if straight by ?.  You'd be surprised how they still will run with one bent as you say 

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