Hmmmm Ring failure

[noobi]

Well my 125 finally died last weekend, It just locked up for no apparent reason, I hadn't drowned it, wasn't giving it death, it wasn't getting hot.
Upon inspection it seems that the ring rotated in the bore and broke off on the exhaust port and lunched the piston and head, and deposited some nice bits of piston in the cases as well.
Looks like its in for an overhaul.
Im not too sure what to do about the head though, its got some nice ring shape dents in it now, im thinking get the damage machined out, then getting the base planed to keep the compression and squish relatively the same.
Ill post pictures soon

[gasmonkey]

Sounds like the ring over rode it's positioner pin in the pistonring groove.
Push the bike into the corrner and fiddle with it later.It'll start raining soon(i hope) giving you plenty of time then.
That bike's been a good test bed to hone your spanner skills on.

[gg3]

Bad luck Noobi,how many hours did you have on it? Ummm...fit a 200 barrel kit project ?

[noobi]

Around 100 hours, but Iv never used it on a mx track, and had a clean airfilter every ride or at least every second. And I wasnt stressing the engine when it happened. Oh well, you cant put a 200 barrel on as its not he way the engine is designed, the 125 uses cases and crank etc thats are only used on the 125, the 200 has the cases from the bigger bikes, with a different crank and barrel.
I might look into making a 144 though....

[noobi]

[Rick]

Ouch!!!! by the looks of things it looks like something came un-glued! That piston is pretty scared, like something let loose in the combustion chambem. From the looks of that plug it looks pretty lean....

Good luck

[noobi]

The marks in the middle of the piston are from me bashing it with a screw driver it get the piston un stuck, thats probably not how I should have done it, but I wanted to see what the condition of everything else was like, and I knew the piston was toast anyway.
Im hoping the bill to re plate the cylinder isnt too bad

And yes, that seems to be the general consensus is that the locater pin broke/fell out and the ring rotated. Its my own fault for not changing the piston sooner