HELP... main bearing/case problems!

[bunk]

So here are the cliff notes... bike broke, fixed bike, bike runs great for about 4 hours, bike breaks again, now I have issues I need help with.

In riding I noticed an excessive vibration.  Checked everything out and yes the crank bearings were shot out.  The motor was ripped out and completely rebuilt, new top-end, crank rebuilt, all new bearings/seals.  All the work was done by a recommended bike builder here in town.  I got the motor back and it runs perfect, ran it through a couple heat cycles to make sure everything gets seated ok.  First ride out everything is great, the bike runs better than ever for the first couple hours.  Then just out of nowhere while at steady throttle it starts to vibrate again.  I shut it down, load up and take it back to the guy.  He first thinks that the bearing gave out.  Rips it apart to find the bearing is perfectly fine, but the sleeve on the left side case is warn basically allowing for slop.  Some phone calls are made and we find a used left side case.  In checking it out, we find that that case too has been spun out also. (which is probably why the guy bought new cases)  Oh any btw its an 01' 500 with fairly low hours on it.

So... my question is, where do I go from here. 

-buy a new case, or even both sides just to be safe?
-send my case off and have it re-sleeved? If that is possible?
-??? you tell me

Sorry for the long post, I just wanted to make sure I had all the info on there of what's going on just in case.

[tharden]

You might be able to have it welded and machined back to fit.  I probably would just buy some new cases too and be done with it.

[bunk]

From what im finding, you can only get the cases in pairs and from Kawi they want $6XX and from the local shop where i get all my stuff from they can get them for $510.  Anywhere else that might be a bit cheaper??

[The Flyin Hawaiian]

I have seen where some vintage guys repair the cases by machining out the bearing area and pressing in an insert. It seems to work well.

[don46]

I have seen where some vintage guys repair the cases by machining out the bearing area and pressing in an insert. It seems to work well.

I've seen this happen before and as flyin says you can bore the steel insert and install a sleeve, then have it bored to the proper diameter. The cases are sold in pairs, in theory they are matched when bored, if I was in a pinch I would use one from another but would rather not if I had a choice. left side cases are the hardest to find, I think because of thrown chains eating the case. You could look for a set on ebay, but then you might end up with the same thing you already have, or bite the bullet and shell out for a new set. in the end it will be worth it.

by the way, I think mis aligned crank account for the problems you have experienced.

[barryadam]

http://www.mce-racing.com/

Call Kevin.  He has a KX500.

He has been providing the resleeving and reboring of roadrace crankcases for many race teams.
Don't know what he'd charge for a KX, but he was reasonable for the work I had him do.  And very knowledgable and experienced.  Recommended.

[BDI]

This is typical kx500 stuff, This is why you should use the heat the cases and cool the bearing method to rebuild. You can get new cases for around $350.00 ish from midwest action cycle. Buy new cases, you will be helping us all because if people keep buying new kx500 hard parts like cases kawi will keep producing them.

[martinfan30]

Where do you feel the vibration? Hi RPM? Low RPM? Just curious... Is it very noticeable?

[The Flyin Hawaiian]

Funny, after I replied to this thread, I split my cases on my 04 KX250 to replace a crank seal, only to find that the ignition side main bearing insert is worn and the bearing just falls out. Now Im contemplating putting my 02 500 engine in it.

[cbxracer30]

Bunk,  I have guys I race with that have had both welded and resleeved their cases both methods have worked but the kicker is finding a quality guy to do the work, for the right price because some guys will want almost asuch for the repair as the price of new cases.You also have to consider the fact that if that race is worn most likely the races on both ends of the clutch/tranny shaft that are in both cases are probably worn also, I've seen them go also.