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99ish CR 125 Knock/hangup and glitter in the oil :(

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My nephew brought his bike over today saying it sounded like something was wrong.  We changed the oil (planned on doing that anyway!), the oil was black, not milky, but had considerable glitter in it.  We could hear a knock coming from the transmission or bottom end.  So we pulled the chain, and you could feel something catch whenever you rotated the drive sprocket past a certain point.

 

After changing the oil, we rode it, I couldn't hear anything while I was riding it, except when coming off a little jump, I could hear a high pitched, but not very loud, squeal.  My nephew said it sounded like it was making a grinding noise when he shifted. Maybe my hearing is just gone, but I never heard it.

 

After about 5-10 minutes, we changed the oil again.  It was black, same as the old oil, which had quite a few hours on it.  It also had a lot of metal in it.

 

Any ideas?  I'm handy, but have never rebuilt a bottom end.  I wouldn't even know what to look at, would it be obvious? The bottom end is pretty new, someone else rebuilt it late last year.

 

Thanks for any help.

 

Marc

 

 

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Is it possible this is actually a top end issue?  With the oil turning black so quickly, the only thing I can think of is burnt gases/oil getting through the cylinder into the bottom end.

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1 hour ago, Marc Fonger said:

Is it possible this is actually a top end issue?  With the oil turning black so quickly, the only thing I can think of is burnt gases/oil getting through the cylinder into the bottom end.

Crankcase and transmission lubricants are separate from each other outside of the right main seal. This is a tranny issue and my guess is it's something more like a mainshaft or clutch hub bearing may have grenaded. Only way to be sure is to split the cases and find out. Metal shavings in the oil is a bad sign and continuing to ride it is just allowing that metal to trash everything else in the clutch compartment and tranny....it's just carrying it around to all the other parts. 

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Sloryd66 you are absolutely correct on not running it, and on the oil issue, not sure what I was thinking!  But I still do not understand why the oil would turn black that fast. . . .

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4 hours ago, Marc Fonger said:

Sloryd66 you are absolutely correct on not running it, and on the oil issue, not sure what I was thinking!  But I still do not understand why the oil would turn black that fast. . . .

one reason is that you cant get all the old oil out, in turn making the new oil look dirty... Its time to split the cases and do a complete rebuild. good luck

Edited by mxsteve1968

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7 hours ago, Marc Fonger said:

Sloryd66 you are absolutely correct on not running it, and on the oil issue, not sure what I was thinking!  But I still do not understand why the oil would turn black that fast. . . .

aluminum clutch plates

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Finally got the bike tore down, a bearing inside the L crankcase exploded and the case is damaged.  Went on rockymountainatv to replace it, but there's two options for this year and the serial number plate for the engine is missing.  Any idea what the difference between the two cases is??  This is what the website says: 

311200-KZ4-L10

(replaces part #
11200-KZ4-A90)

CRANKCASE, L. | Use up to Engine SN 6108066

 

Any help would be greatly appreciated.

image1.jpeg

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