Piston and Cylinder pics

[95formula847]

Hey whats up guys im posting this for a freind. I have a 91 KX500. He just bought a 96 KX250 roughly a month and a half ago and hes had a few problems with it. First, it fouls plugs like crazy. Second, you could start it with your hand. I could literally push the kickstart with my hand and start it.

The other day he was ridin around and it just shut off on him out of nowwhere and wouldnt start. So we made sure it got spark and it did. We pulled the carb and it was clean. Its getting fuel and everything. Now when we try to start it...its extremely easy to kick over and barely any air comes out of the exhaust.

This led me to believe it had piston issues. So we pulled the cylinder and this is what we found.









The piston has huge gouges and chunks missing on the top and also has a very long/deep gouge running up the side which you can see in one of the pics. This gouge is also reflected on the cylinder. The cylinder is just as rough with gouges and chunks missing near the openings. What could have caused this? Also every few kicks of the kickstart would act like it "let loose" it wouldnt turn the engine over but u could kick the kickstarter. Any help would be awesome.

Also the rings are pretty loose. The gap when the piston was out was 3/16 of an inch. Sorry he didnt have any other for of measurement other than a tape measure.

[jinxy]

the barrel is worn to the point where
the plating is flaking off,this then caused the
piston to bind with the clinder causing debre
to hit the top of the piston
get the clinder replated with a new piston
and rings all should be ok
check your head for the same marks
as the top of the piston
j

[hughes]

For some reason I'm unable to see the pictures, but if debris has went through the engine then the entire bottom end needs to come down to do the job correctly. My advice would be to split the cases so the crank area can be cleaned properly. I would replace the main bearings and the rod bearing. Once the bottom end is cleaned and new parts installed then need to get cylinder replated and order top end piston kit. There's no way to properly flush the bottom end of debris without taking it apart. It only takes one small piece of metal debris to wipe out the new plating or top end you just installed.

[jinxy]

yes agreed as above
when i rebuilt mine it was similar condition
i needed to do the main bearings any way
best be on the safe side and split the casings. stick some new mains and seals
in as they are only cheep
j