Author Topic: HELP!!! KX500 CHAIN RUBBING ON CRANKCASE  (Read 2271 times)

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Offline 98kaw5oo

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HELP!!! KX500 CHAIN RUBBING ON CRANKCASE
« on: August 02, 2008, 03:55:05 AM »
i have searched and found other topics on this but they still do not explain exactly why the chain is rubbing on the case.i have the protector right in front of the sprocket but its not hitting there,it is hitting on the inside above the ("lip")it doesnt rub with the bike on a stand in storage but it looks close and it must hit when its running under tension.i believe the chain on the bike is not an o-ring,just a cheap chain.i am running stock gearing with a jt 14" front sprocket,my o-ring is inside there,the collar is there,seal is there which i will replace due to small leak.nothing seems to be worn out and there is just enough room to put on the clip to hold the sprocket on,i have heard things about grinding down the face of the sprocket and putting a washer behind to bring the sprocket farther away from the case.the thing is these bikes did not rub against the case when they were brand new so should i just replace the 0-ring,collar,seal,and put on a factory oem sprocket?is the jt a wider sprocket? any suggestions??? offset sprocket? thinner sprocket? thanks.

Offline dsrtrider

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Re: HELP!!! KX500 CHAIN RUBBING ON CRANKCASE
« Reply #1 on: August 02, 2008, 05:47:58 AM »
i haven't had rubbing problems but i just replaced my sprockets and chain with new 114 link o-ring and noticed again i have small leack from the rubber seal.  can't seem to get that to stop after replacing it a few times.  i took off the metal chain/case guard and just have plastic chain guard cover
current bike 2007 ktm 300 xc-w - keeping two strokes alive
1994 kx500 -sold-made me the man i am today

1990 kx500-sold
1982 kx250-sold
1979 rm125-sold
1978 kdx125 -sold
1977 xr75 - first bike

Offline KXcam22

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Re: HELP!!! KX500 CHAIN RUBBING ON CRANKCASE
« Reply #2 on: August 03, 2008, 05:57:47 PM »
98 Kaw,
  Generally the problem starts when you put an aftermarket chain on. Depending on the chain quality, the side plates are thicker and when combined with an oring, makes the overall chain substantially wider.  My K5 didin't rub too bad but I machined a pocket (lathe) in the sprocket and used a thin washer behind it to space the sprocket outward.  End of rubbing.  I had the same issue with my 450 but the fix was easier due to a different sprocket mounting method.  I used a chevy350 valve spring shim 0.030" (got a used one for free at a machine shop) to space the sprocket out. Incidentaly this same shim fits the KX500 CS shaft perfectly ( I tried it) so would be a good start for someone who was going to machine a pocket.  Hope this helps. Cam.

Offline 98kaw5oo

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Re: HELP!!! KX500 CHAIN RUBBING ON CRANKCASE
« Reply #3 on: August 03, 2008, 06:08:47 PM »
thanks cam.ill try that chevy 350 shim/sprocket mod.

Offline 98kaw5oo

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Re: HELP!!! KX500 CHAIN RUBBING ON CRANKCASE
« Reply #4 on: August 05, 2008, 05:26:43 AM »
cam,can you explain exactly and with measurements how to do the sprocket pocket cutout,i imagine its a pocket for the  sprocket clip to recess into the sprocket?