Destroyed piston!

B

BoardTrackBomber

New Member
Well I thought I'd shard this with you guys since it's been a minute since I posted last.. Luckily, had a spare piston and jug laying around. 15 minutes later up and running again!!! The simplicity of these things just can't be beat.

I also cut the skirt of the piston on the intake side by about .060" on the new piston and it has made a difference in power, the little CG screams now harder than ever before!!!





 
Do you know what caused that damage? Any evidence of a broken piston ring, or debris in the cyclinder?
Surely you are mixing oil with your fuel. I had to rebuild an engine that my nephew ran without oil and the piston looked much like yours.

Glad you had spare parts and are back on the road. Good luck.

Tom
 
I think what killed this piston was overheating. Me and a buddy were riding our gasbikes for 89ers weekend through parades, the carnival, car shows, etc. I think that all this low speed cruising is what was the demise of the piston. An air cooled engine needs air to be cooled, who woulda thought!?!?

No, there was no evidence of a broken ring or debris inside the jug.

Wait, you're supposed to mix oil with these things!?!?! :D
We've been running a ratio of about 36:1 with good results.

My gasbiking buddy paced me in his car and clocked me at 42 MPH top speed on my bike, averaging about 36 MPH. Haulin ass on a bicycle!
 
Got any pics of your carnage? Would like to see em if so!

Here's something I'm wondering. The jug that was on the engine when this happened has some small pieces of the piston embedded into the cylinder wall. No scoring, no cracks or anything like that so I'm wondering if I can hone this cylinder and reuse that jug in the future?

I know the jugs have chrome plating on them so honing may remove some of that as well, but it might be worth experimenting for fun.
 
Honing will destroy the chrome and the rings will seize and/or gall the cylinder.
 
I'll dig it out of my parts-box tomorrow and post pics; I've since replaced the top-end. Don't hone, rather use a Dremel with small grinding-wheel to lightly grind down prominences on both jug-wall and piston. I have a set of precision files I've used to file out the ring-channels in cases of channel deformation after a detonation. You can use a piece a broken ring to gauge the filing progress. Provided that the jug gouge isn't significant, a new set of rings and a mini-break-in should suffice. My FIRST detonation destroyed only the top ring, squished the top piston channel, and crunched the jug-wall in the combustion-chamber just over the transfer-port. Using the techniques herein I was able to limp along with the repair until new parts arrived. This included my moving the bottom-ring to the top ring-channel to replace the broken one and to assure highest compression. This all said, I can't advise you enough to make sure no debris was left in your crankcase after this incident. BTW: how is you upper needle bearing? And your wrist-pin retainers .
 
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