Found this in my cylinder. Anybody have any clues?

[washannon]

Just had out on new rear tire, chain and sprockets and chain guide/slider on my '11 kx250f, pulled it out into the yard to ride it around to make sure everything was in working order before loading up for the races. Bike started on the third kick as always. Idled for about 10 second and died. Started again in 3 kicks but was making an awful rattling sound. Pulled the head and found this sitting on top of the piston. Anybody have any idea what it is? Going to put a new piston in it now. Luckily the valves seem to be alright aside for a couple light "marks" on the left intake valve. I know it's hard to tell much in the picture, but would you run it like it is? Only have about 20 hours on the bike since new. The marks on the valves can't be felt, really more like it just kind of cleaned the carbon off. Thanks for any input.

[Peterrides]

Kinda looks like a woodruff key.

[Hans Schmid]

Looks like a KTM fanboy sabotaged your bike....

As for "what it is" I have no idea...How did the cylinder look? What about the piston?

Edited September 7, 2013 by originalmonk

[washannon]

Looks like a KTM fanboy sabotaged your bike....

As for "what it is" I have no idea...How did the cylinder look? What about the piston?

Cylinder and piston both look fine. I was just very curious as to what it was. It was at some point a functioning part. It is folded in half and has the notches on each end and was probably .02"-.03" before folded. Just realized the clutch isn't working either. Lever pull is smooth and I can see the plates moving, but it isn't disengaging.

[Dragon67]

I would be interested to know what that thing is. Pic one isn't too clear. Maybe unfold the thing and take another pic. Is it aluminum, steel or stainless? Anyway, there's only one way in, unless you had the head off or the throttle body off. Do you have a backfire screen? I doubt this is linked to the clutch, but if so it would be even more interesting. Please let us know if you figure it out.

[washannon]

I would be interested to know what that thing is. Pic one isn't too clear. Maybe unfold the thing and take another pic. Is it aluminum, steel or stainless? Anyway, there's only one way in, unless you had the head off or the throttle body off. Do you have a backfire screen? I doubt this is linked to the clutch, but if so it would be even more interesting. Please let us know if you figure it out.

I've never had the head off, had the air box off maybe 3 weeks ago, I've rode 4 times since then. Backfire screen is still in. I'll try to get some better pics and attempt to unfold it tomorrow. It's closed up pretty tight and I'm pretty sure it will break. 99% sure it's aluminum.

[Dragon67]

There are some aluminum (maybe stainless? but I doubt it) rivets holding the air box together. They look like those things you use to fasten stuff to drywall. Maybe a tab broke off on assembly and found its way in. It kind of looks similar to that. I would check the air box to be sure nothing else is in there. While the head is off you can turn it valve side down and put alcohol or whatever in the intake and exhaust ports to see if you have a big leak. If a valve was bent, that will tell you. Keep us posted please.

[washannon]

There are some aluminum (maybe stainless? but I doubt it) rivets holding the air box together. They look like those things you use to fasten stuff to drywall. Maybe a tab broke off on assembly and found its way in. It kind of looks similar to that. I would check the air box to be sure nothing else is in there. While the head is off you can turn it valve side down and put alcohol or whatever in the intake and exhaust ports to see if you have a big leak. If a valve was bent, that will tell you. Keep us posted please.

I know the pieces you're talking about, and I think it does look similar. Hopefully I'll be able to get out to the garage for a bit tomorrow evening and check that out. Already leak checked the valves and had nothing pass through so I think I'm alright there. Still have the clutch issue to dig into hopefully tomorrow also.

[washannon]

Just realized what it is!! It's the aluminum clip that goes around the air temp sensor to help seal it into the air box. Guess it just took it a while to work its way down past the throttle body and into the cylinder.

[washannon]

I will check tomorrow to make sure it's missing but I'm 99% sure that's what it is.

Edited September 9, 2013 by washannon

[washannon]

I was correct on it being the clip. I guess it fell out when I put the air box back on and just took a while to work its way down. Does anybody know if you can buy that piece separately or if it comes with the boot or the sensor? Can't seem to find it in any diagrams. Got into the clutch a little bit also. All the fibers and plates are moving out with the pressure plate when you pull the lever. Fibers and steels all check out within spec, and the hub doesn't seem to have any grooving or notching in it. Any ideas what could be causing this? I pulled everything out and reinstalled it and I'm still having the same issue.