Damaged cylinder plating

[Foil]

Howdy. I posted this up on thumpertalk as well, but this forum gets more traction on the gasgas stuff.



I need some opinions about something that will never have an ideal answer.



Long story short, I swapped out the piston and main bearings at around 600 hours and within 4-5 hours the right side bearing cage failed. Luckily it wasn't in the field, I had just washed the bike and was tooling around to let it dry completely until a loud screeching started and I shut it down.









(the orange stuff is silicone - I usually smear a bit around the crank seals just as a precaution for case/ seal imperfections. It looks like a lot, but it really is just a smudge)

The damage on the cases wasn't too severe. The inside was fine (god knows how) and the outside is a bit scored, but nothing too serious.



Currently I'm waiting on an answer from motocrosscenter to see about warranty. This is not looking great, since they slapped me with a "we've reached out to the manufacturer and are waiting for a reply" for almost a month now- I might need to be a bit more persuasive.



The main problem right now is the cylinder. Somehow a chunk of the bearing cage made it up to the cylinder and left some marks:









This was a real kick in the dic...wallet, since the cylinder was really fresh before this whole ordeal. The scratches aren't "too bad". I can kind of feel them, but they don't go all the way through the plating. The chip however is a real bastard.



Right now I'm running an old cylinder just to get by, but it's really worn out and I get some piston slap, especially cold, but on decel while hot.



I'm not really in a position to fork out another 600€ for a cylinder/piston combo right now, so here's the million dollar question. Would you run this cylinder?

 

[gasgasman]

Sorry for your troubles.
Look into replating the cylinder.

 

[(F5)]

Sorry, hard to tell from pictures. Chip? Is that the mark by the transfer in pic 1?

The question is, will the ring pick up on it and can you really see aluminum through there? Or am I missing seeing something?
The piston is moving real slow near the ends. The compression doesn't build until the exhaust port closes of course.
A hone with proper plated bore hone may tidy it up.
All cylinder replating places will have the equipment. They can assess he damage at the time.

So, 4 to 5 hours on main bearing? That's awful luck.
Or you have an installation issue, bent crank, or lubrication issue ( would show up with nasty bluing I'd expect.

 

[Foil]

Yep, that spot is chipped all the way to the aluminium. The scratches aren't quite as bad, but you can definitely feel them with a nail. Keep in mind that these pictures were taken after a clean and a stone hone, so it won't get better than it is.

Like I said, from assembly to failure was around 4 hours on that main.

I know it sound defensive, but I'm sure it wasn't an installation problem - I did the previous bearings the exact same way, along with the bearing that's in it right now (just changed the offending one). The crank seems to be fine as well, since I have put another 10 or 12 hours on it since slapping things back together.

The carb settings are the same, same oil, same gas supplier, no strangeness whatsoever up until the failure.

In fact, the bike was much better than it is right now, since it had proper compression.

 

[(F5)]

Oh well, replate time. Pity but safe.
Not defensive, just a point to consider as they are usually reliable.

 

[Foil]

Thanks for the feedback. Just got a few words back from motocrosscenter. They did refund the bearing kit + gaskets, but the rest. Well, it is what it is.

 

[Foil]

Just an update to move things along.

I did end up buying a new piston (b) to go along with the damaged cylinder. I've put around 10 hours on it (about 4 at almost race pace) and everything sounds/feels pretty good.

I will keep the older/worn out cylinder as a core, but the piston slap was atrocious.