02 CR125 SE bearing failure? HELP!

[Zenith]

Hi guys, I'm looking for a bit of help here if you don't mind...

These pics are from a 02 CR125 running on std Unleaded petrol, 8 plug, 32:1 fuel:oil and is jetted reasonably well to the best of my knowledge(It's not actually my bike). It has a Cometic thin base gasket with two head gaskets to compensate. The piston is a Wiseco, about 2 months old with few hours on it, it was correctly run in. One thing though, the small end bearing was a spurious make sent to us by our supplier, I suspect most of you are going to say this is the problem :( and I'm inclined to agree, I just want to be sure(We'll certianly buy Honda or Wiseco from now on)! The filter was spotless and there was no dirt in the engine. I haven't heard the owner complain about detonation but I'm not sure he'd be aware of it if it occured so it can't be ruled out.
Anyway the bike lost compression on the MX track the other day, no big bang or anything, it just bogged down and cut out. After he pushed it back to the pit the compression had returned, it looks now like the ring was stuck in the groove after the engine failure, then just freed up; this probably isn't significant, just thought I'd mention it in case. He didn't restart the bike or anything, just brough it home and stripped it down.
So you can see in the pics what he found, the small end has broken up and some of the bearing case and needles have worked their way into the combustion chamber, destroying the piston and fairly mincing the head. There are light scores down the piston skirt but the cylinder plating is fine besides some chips to the port windows. The bottom end feels fine but we will flush it out fully to be safe.
So I guess I have a few questions... I'll just mention that the guy doesn't have a heap of money at the moment so we can't risk just rebuilding and hoping for the best :)...

1. What happened!?! I have never seen detonation damage but suspect the damage to the piston was not caused by detonation, but just by the bearing fragments?
2. The deepest gouge in the head is about 1mm, can this head be safely repaired(skimmed is it?)? And if so what specs should we ask for, is there a better squish angle/band size or dome shape(For std European unleaded) we should get while it's being done?
3. Is it OK to fix up the small chips in the port windows with a Dremmel or similar, if so any tips for making sure we do this right? BTW. There is nobody in this country that can do this(That we can trust anyway) before you suggest getting a local guy to do it... If necessary we can send it to the UK but this is last resort because of shipping costs, exchange rate etc.
4. The bearing runner in the top of the conrod feels perfect but is there some good way to check it?

Thanks VERY much for any help it's much appreciated!

Philip

 

[bclapham]

oh dear! it must have been a bad week back home since marcus messed up his KX in a similar manner with a duff plug.

just out if interest, did you get a name on the bearing? there was a website selling cheap pistons, bearings and rings for jap bikes, i tink they were made in europe, but i feel this might have "meant" former eastern block countries.

did you get a squish clearance measurement before it broke, maybe you can get a simple clean up on the head and just run 1 gasket? good luck

 

[Zenith]

I forget the name on the se bearing, it was in a decent looking shrink wrapped pack. I've used them before once or twice without problems but... Then name was something like MotoX or MotoWerx or one of those mad generic names that you'd swear were generated by a computer...
Didn't get a squish clearance unfortunately.

I have the piston etc hear by the way if anybody needs more info or pictures just let me know...

Thanks

 

[marcusgunby]

Philip a few questions
did the piston have a window in the back? as this aids lubrication to the little end bearing.
From the photo i cant see signs of detonation so i dont think thats the problem(detonation will however put a huge strain on all bearings)

I do think its a case of cheap bearing=expensive repair(just like my blow up BTW-cheap plug in my senario)
The head could be repaired but its going to need alot of machining and he may have to run a spacer on the spark plug to compensate for the amount of material removed from the dome part.When its machined you want to have it modified to this spec
volume same as previous(put it on a perspex plate-greased at the edges, the perspex needs a small hole to fill the head, with a syringe measure the volume.
The angle of the squishband should be 3 degrees(std is zero degrees)
the step from the head to the combustion chamber keep the same(0.75mm i think)
squishband width 6mm
i know this is hard to understand when reading but im not able to draw stuff on pictures so if you need to, ask me to explain.
After all that it might be easier to buy a new head.

If the top hole in the con rod looks perfect i guess you were very lucky-however its very hard to flush the bottom end of all bits-it really is only possible to know by splitting the engine-if you dont the exact same thing might happen.
Hope this helps.

 

[Zenith]

The piston had a window, it was just the std Wiseco 676 series. I forgot to mention we sorted out that airbox/boot problem the 02s had a few months back so we're almost certina dirt is not the issue.
One thing is over the last few weeks the owner ran a tank or two of Putoline MX5 and a tank or two of Castrol R2 through the bike(without necessarily draining out the TTS mix first).
So does it sound as though if we get a decent SE bearing(Wiseco/Honda?) and run a consistent oil this problem won't happen again? I know you can never be sure but I want to be 99% at least :)...

Thanks for the replies!

 

[marcusgunby]

I would be 90% sure it would hold together, as long as you are sure no bits entered the bottom end.However mixing those types of premix isnt a good idea-ive seen some turn into a thick precipitiate when mixed.