IndyMX

Crash Test Dummy
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Jul 18, 2006
5,548
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Amo, IN
My nephews bike (2007 KX85) started making a really nasty squeal when we were riding weekend before last.

It's quite loud and sounds like it's coming from the crank on the ignition side.

I took the ignition cover off and gave the flywheel a good shake, no noticeable movement.

I took the clutch side cover off and inspected everything. I found that the KIPS valve regulator bearings were bad, and replaced them.

I thought this might solve the problem, but after I put it all back together tonight and ran it, it still has the noise.

I also took the cylinder off and checked the rod & wrist pin bearings, they are fine. No movement up and down that I can feel. I almost lifted the bike off the stand with the rod.. No movement detected.

Cylinder and piston looked fine. KIPS valve looked good with the exception of a little bit of carbon buildup. Cleaned it off.

I am almost certain that either bearing on the clutch or the crank shaft bearings. It stays the same with the clutch pulled.

But, I was under the impression that if the crank bearings started to go, it would have some movement up and down?

Am I wrong about that?

Should I just go ahead and do a complete bottom end on it and also replace the bearing on the clutch?

Has anyone ever had something like this happen?

After it started making the noise, he rode 3 or 4 laps before I heard it and made him stop.

Oh.. Yeah, the bike still has plenty of power, it seems fine except for that extra loud bearing noise. Almost sounds like a bearing running dry.

TIA
 

darringer

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Dec 2, 2001
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Still could be crank bearings even though they are tight. Pull the plug and rotate the crank to feel for roughness. Almost sounds like something is binding, although it's hard to tell from the cell phone. Could even possibly be the mainshaft bearings in the tranny. They spin whenever the motor's running, like the crank. It's hard to diagnose noises in the transmission, as the sound "travels" through the cases and can mask the culprit. You may not find it and have to split the cases and check all of the bearings.
 

IndyMX

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Jul 18, 2006
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Amo, IN
Yeah, it's really starting to look like the cases are going to have to be split..

I am pretty sure it's not the trans, as it still sounds about the same with the clutch pulled.. And when the clutch is pulled, the trans does not spin.
 

IndyMX

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Jul 18, 2006
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Amo, IN
At 12 years old he has no concept of cash...

I saved my brother some coin though! Nephew likes me for just being his uncle.. Plus I beat the crap outta him whenever possible.. He likes that for some reason. Strange kid.
 

IndyMX

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Jul 18, 2006
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Note the groove in the side of the bearing..

The seal has wear on it too.. It appears that they were mashed together, which would account for the squeal. And also tells me why I didn't feel any movement in the bearing.

I'd say that without addressing this, it would probably have resulted in the bearing failing quite soon.. Not only that, but the seal looks as though it was pretty much trash.

Can you say, caught in time!
 

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IndyMX

Crash Test Dummy
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Jul 18, 2006
5,548
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Amo, IN
All four?

Seals & bearings you mean?

Yes.. absolutely.. I'll have the seals tomorrow, but I already have the bearings.

Then I'm just waiting on a clutch side cover gasket, and I'll be able to reassemble.
 

IndyMX

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Jul 18, 2006
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Both bearings & seals are gonna get replaced, no doubt.

No blind puller required!

Going to Peoria Sunday for the TT race!! whoot!
 
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