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Post by tiny on Aug 25, 2019 10:50:26 GMT -5
Wow mate I've seen alot of self destruction in an engine but never a complete melt down of the piston.
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Post by GrumpyUnk on Aug 25, 2019 10:50:39 GMT -5
Holy Piston, batman... really holy. Far as I can see, a valve self-destructed, and the tulip end was bounced around on top of the piston, between piston and head. You can take it apart by splitting the two halves of the block. Most bolts on the flywheel side.
Likely some bits of metal in the crankcase. You can toss & replace, take apart and clean, or just remove the filter/screen and drainplug and flush the crud out. Odds are any chips will fall to the bottom and wash out, but, they might not. If the crankshaft rotated for any length of time, chips & bits COULD have circulated and gotten into the bearings, rod, and the mains at either end of the crankshaft. The bearings are ball bearings, and open to any and all thats within or carried by the oil. It all depends on how large your wallet is. It's possible to just replace the piston, rings, cylinder and head, and get away with it, but you run the chance that there may be some bits that did not fall to the bottom of the crankcase. Metal bits won't float, but should drop to the bottom. You pays your money and take your chances. New short case 50cc engines are available on the web at multiple sources. Ballpark around $300. You may be better off buying a parts machine, but it is a pig-in-a-poke... You can take it apart, clean/replace rod and main bearings as needed, and put it back together. Then install new cylinder, head, piston and rings. You'd be as good as new at a bit lower cost than complete replacement. You should watch some of the youtube videos on replacing the bearings. A fellow in India or Indonesia or close does it, and shows how to align the two halves of the crankshaft so they run parallel and the connecting rod journal runs true without side-to-side wobble. It is an art to assemble a multi-piece crankshaft, IMO. If your rod bearing was not damaged, you might be able to just replace the two main ball bearings if they are damaged. Check the bearings by 'feel' of the smoothness in rotation. If there is ANY evidence of roughness or resistance to rotation(a rough spot), they need to be replaced. They might just need to be cleaned, and that limits cost to the gasket set, and again the upper portion of the engine. You may be able to re-use the cam & followers & chain. All depends. tom
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