Went to a local drag race competition yesterday. I was sitting on the line getting ready to run my first race, and the btch just quit. At first I thot I may have fouled a plug, then I thot my carb was messin up. But today I did a comp check and I only had 75lb. When I tore it down this is what I found (see pics). The cylinder wall is spotless, but there was definately something in there that wasnt sposed to be. The top ring is stuck also. The ring lands are all in tact, and the crankcase is clean. I am mistified. It didnt give any warning at all, it just felt a little slow. The weather was really hot and humid, but my temp never got over 150.
Anyone ever seen this? Something made all these holes ond nicks, but what was it and where did it come from, and where is it now? [img]i/expressions/face-icon-small-disgusted.gif[/img]
Oh yeah, the dome looks kinda funny cause I painted it so it mite show up better in pics.

 

wow I'm sorry to hear that [img]i/expressions/face-icon-small-frown.gif[/img] were both wrist pin clips still in place when you tore it down?

 

Things that come to mind. A small nut or bolt, piece of sparkplug, piece of piston or bearing, reeds, lost carb jet?

 

piston wash are horrible,,it seem the bore wasn't at good enough,,,
it is typicall with big oversize piston,,,get a stock bore piston and that will never happen again.
i never seen a wear out piston like this,what oil is in that thing?

 

You may want to check the connecting rod bearings ,mine looked the same way when it went out.

 

Yep, something did a dance on it for sure. Had to be a piece of metal because detonation wouldnt be that dramatic. Check the reedcage and make sure all the screws are there as well.

 

Well, both wristpin clips were in place. The motor is 40 over, and was done by HPD. Im running Amzoil at 36-1. The V force reeds looked flawless, but ill look closer at the screws that hold them together. Now the only thing that isnt new in the bottom end is the lower connecting rod bearing. Its got some play in it but its supposed to be like that, rite?
Theres nothing in the botttom tho, I removed the case plug and washed it out with break clean, into a clean container. Just 2 or 3 shavings that you can break up with your finger.
So I wonder why the top ring is stuck? And the bottom ring is partialy stuck?

 

Look real close at the bottom rod bearing ,look with a flashlight thru the little slot.When i looked at mine real close i could see the pins where almost completely sideways instead of being straight across.

 

bummer

My buddy had a blaster that looed like that. Wristpin clip

 

What ever did it was kinda flat, and had a square edge to it. Almost like the end of a spark plug. Or like a pice of a ring. But the rings are all in one pice, and so is the plug. Im gona borrow a dial indicator and measure the runout, on the bottom rod bearing. The side to side play is around .5mm & the service limit is .9
Man I hate to split these cases if I dont have to.
Also what do you fellas think about the dome? Would you replace it, or just try and clean it up with a little stone in a die grinder?

Thanks for all the help,
Brent