Dropped exhaust valve

[Geoffb18610]

So my knock was an exhaust valve in the combustion chamber. The piston is beat up pretty good, but cylinder wall seems no worse for wear. The head has a couple of scars on it, but seems structurally sound, and seat appears undamaged. I have all new parts to replace piston and valve, but I don't have a new plastic "retainer" that goes in the second groove on the valve, below the keeper. Can't even find a listing for it. Do I need it? Where can I find it?
Thanks

[sctrailrider]

Ex has a oil seal, intake doesn't, they both have a rubber o-ring thing that fits in the lower grove..

gmparts online should give ya some numbers....

[Geoffb18610]

Thank you

[JohnC]

Did you figure out what happened? It'd be a shame to spend all that time and money fixing it just to have it happen again.

[Robyn]

There is only .045" between the top of the piston and the head at TDC

Did a piece of the exhaust valve break off ??

If the entire valve head had dropped the thing should have really done some serious damage, like knock out a cylinder wall.

Post some pix of the broken parts

Robyn