Author Topic: Kx500 main bearings  (Read 3114 times)

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Offline Ims Roll

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Kx500 main bearings
« on: October 14, 2016, 02:32:48 AM »
Problems have plagued majority of my WORCS season on the ol' five hunitt...

Short back story and on to the current issue...

Round 3 in Havasu left me with a broken case (rock got stuck between the chain and the case saver and blew the clutch actuator out of the cases)
Month later I managed to locate a complete bottom end, upon splitting the whole crank case had been blown into the tranny... no good once again.

Fast forward to now and my new to me 3rd motor, which was purchased with the entire bike running. After splitting the cases last night it appears to me that the main bearing race are extremely worn and I would guess junk.

So for the questions...
How worn is too worn? (I have an idea on this answer but please amuse me)
What can I do to fix this?
Do I risk loctiting the mains in, or is this even fee sable?
Have a machine shop mill the races out and press in a new one?

What are my best options? I kind of need the bike to be ready by next Saturday as my other "evo modern" bikes are not really race ready, if it can't be done it looks like I will be racing my trusty KLR 650 for the last round  :-D
The 2-smoke runs deep in this one...

Offline dave916

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Re: Kx500 main bearings
« Reply #1 on: October 15, 2016, 08:26:36 AM »
Pretty common problem on kx cases/ caused by out of true crank and a pretty weak design of crank
Usually only wear to slip fit [any more machine races or replace cases }
Chances your crank journals could be worn aswell

Bearing retainer would work but does make it a bitch remove bearing again 
I would  bluntly punch  or electric scriber in straight lines the cases in the direction the bearing is going to pressed on{flywheel to web direction} would reduce an chance of spinning
 if you shim the crank to centre on  primary drive side would also help alot{easy enough to do with worn cases]
 
The primary gear side of crank is where the crank is  located  so very important to make sure everthing is solid in that side
High strenght bearing retainer both cases {if worn} / small amount medium grade on primary side crank journal , NOTHING on flywheel side crank jourral [crank  clearance needed for heat expansion etc]

A true crank {even after fitting :-D]and genuine main bearing are the key

Good luck