Miss-Matching Case Halves

My son's brand new 02 kx65 failed a lower end bearing before we got 3/4 gal through it and I noticed that some folks have reported repeated low-hour (less than 10 hrs) failures with the same engine over and over and others have had no lower end failures at all.

FYI: break-in, warm up, 32-1 oil mix, ... all done properly.

My question is that I noticed on the bottom of the cases, numbers were written at the factory in colorful ink on each case half. It looks like one of the digits got slurred from an 8 into a 6 on one case half and may have been miss-matched with a 6 digit on the other case.

Can miss-matching case halves cause repeated lower end bearing failures? It seems to me that if one main bearing location was slightly higher vertically it could put a slight bind on the lower end beariing.

Anyone have experience with this?

(PS: there is a reasonable bump at the machined suface that the cylinder sits on)

here is the latest. I took the engine to the dealer and showed him the miss-match with a straight edge across the two case halves. He agreed that the cases are not aligned on the machined surface that sits under the cylinder. He also agrees that putting in a new crank will result in another crank failure because of this miss-match. But what Kaw is telling him is for me to split the cases and send the cases to CA (I'm in NC) and they will look at them and decide what to do... I am pleased that Kaw is involved and not saying no yet, but man this is turning into a marathon. So, I guess tomorrow I go and get the engine back from the dealer and split the cases... It seem like getting parts so that I can get this running again may take some time...

I offered to send Kaw digital pics of the mis match using a straight edge, but no go says the dealer. He says split the cases and send them to Kaw. Does the Kaw response seem reasonable? At best I will get new cases, crank, ... and I rebuild the thing. If I thought I had a leg to stand on, I would demand a new engine and be done with it...

Is the watch word here patience? Thanks for the guidance.

Well, I had to proceed with me splitting the cases because I had gone so far down that road and the dealer would not budge from this course of action no matter what. If he did the work, he said I would have to pay labor because the most he could get out of Kaw is parts, no labor.

Before I split the cases, I put a staight edge on top of the machined cylinder surface, across the two case halves. Both the front and rear edges left a .0025" gap. So, I split and stripped the cases and expressed them off to Kaw in CA. Hopefully I will know something today. I also put a list together for all the parts needed to rebuild the engine (bearings, seals gaskets, piston, cylinder, head,cases...).

I may need help pressing the crank into the cases/bearings. I can machine spacers to put between the crank flywheels, but I am a little concerned about messing up a new crank putting it in. It took a fair amout of force pushing the old crank out of the cases and I imagine, it will take the same putting in the new. Since the seals will have to be installed in the cases before the crank, heating the cases to make the interference less is not really an option...

Any ideas here as to the best way to press a new crank w/bearings into the cases so that I do not disturm the crank halve's alignment? Also I would imagine the crankshaft should have some side-side movement/clearance, right? I do not see that parameter in the service manual and I was wondering how to insure the main bearings are not bound slightly from the case reassembly.

Thanks again for the help!

First off there is no warranty on KX motocross bikes. I am used to this...
When the engine seized, I thought we stuck a piston, so I pulled the jug to see what was going on. If we stuck a piston, this is always going to be a customer problem and I can handle that. What I found was a seized lower end bearing and I immediately called the dealer. He indicated that he would try to get Kaw to get a new crank etc for me. But he indicated all labor was on me and has stuck to that. Then I call him about the miss-matched cases and he talked with Kaw and they insisted on the cases being split and sent to them for inspection... I really have NO leg to stand on because of the big no warranty sticker on the bike. But it sure would be a LOT better to get a new engine here... I have tried to push on the dealer adn he stands firm that this is the best shot with Kaw because if we piss them off, we give them a reason to not help. Anyway, I would not trust this dealer rebuilding my whole engine, I will make sure it IS right when it goes back together.

As far as the Toyota analogy, there is a BIG difference. Toyota comes with a warranty. Race bikes do not. I have kept the dealer in the situation form the moment I found what happened. Everything I have done has been performed with the dealer instructing me to do so. Lastly, the case match is NOT unrelated. With .0025" of mismatch, it looks like the primary cause, by binding up the lower end bearing.

Back to the main question now... The main bearings on the old crank were tight on the crank and tight in the cases. Is there not supposed to be some axial clearance/movement in the crank? On my race kart engines, it seemed like there was somethign like .010" axial play, so I am wondering why I do not see that here?

And if I use a machined spacer between the flywheels, while I am pressing the crank into the case/bearing, it seems like there should be no possibility of miss-aligning the crank. Correct?

Anyway, I am in this situation... now to make the best of it.
Thanks for the help.
mkandl53