salvageable Engine?

[sojudave]

My bro has a 70cc chengine bike. The other day he said that he was riding it and had a throttle cable issue, so he fixed it and adjusted the clutch because it was a little sloppy too. He said when he went to pedal start it, it would try to turn over. I told him to take the clutch cover off, and the cover for the crank sprocket and try to turn it manually with a scewdriver, you know, like what we do to put a new chain on. He said it wasn't moving. That told me the engine was locked up. He went on and ordered a new one from DAX, and went on an took the engine apart. He sprayed some WD-40 in the cylinder and got the piston to loosen up. After that, he took the cylinder off, and here's a pic:



Between the amount of carbon on the piston and the discoloration on the head, I'm assuming that it overheated due to insufficient oil. Would this be correct? If so, do any of you guys think the engine is salvagable?

[Cabinfever1977]

i think so,clean it up and put it together,and i bet it will start.
u might want new gaskets and sparkplug.
use the proper oil/gas mix.actually you might want a little more oil in the gas.

[Outrunner]

That piston and cylinder look pretty bad. Are the rigs broken? Does
the piston skirts front and rear have vertical scrape marks on them?
What about the cylinder, does it have aluminum from the piston skirt
or ring lands (between rings) imbedded or melted to it? If it does, just scrap it and buy a new piston and cylinder set. Plus you should look at the spark plug to see if there's little tiny particles of aluminum stuck to
the inner electrode.

[Cabinfever1977]

what are you going to use it for,you would have to buy all the parts that go with it,u said your brother kept the parts that go with it and ordered a new engine.you would be better off buying a full new kit for $99 that comes with everything. even if you could save the engine the parts alone would be more than the new kit price.

maybe keep it for parts.
but if you have everything else just buy a new head and piston.

[Retmachinist]

By the looks of the color of the engine studs, that baby got really Hot. I am afraid it is probably toast. Better off, and cheaper to replace it.

John

[sojudave]

well, I was mostly curious. The color of the fins on the head was gold. I told him to check the cylinder walls, and he said that it was okay. I don't plan to use the engine on my current proj. I figured that if he could get it cleaned and the rings checked out, then he's got a spare engine for parts or as a back up. I'm sure I had him running it without enough oil. What can be used to clean the carbon off? I know you can't use something very abrasive because you run the risk of scratching the piston and so on.

[Cabinfever1977]

how about carb cleaner spray and a sos pad used for non stick pans.
or carb/brake cleaner and a washcloth/rag/papertowel/toothbrush your choice.