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piston seizing

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I have a 94 kx250. About 2 years ago i put in a new top and bottom end in ran perfect. about a year ago my clutch went out. Bike sat for about a year, yesterday I put a new clutch in. Put in fresh oil and fresh gas kicked it slow to circulate the oil about 10 times. bike started right up pooring out white/ blue smoke. Before I could drop it in gear the piston locked up. I took out the spark plug drop some oil in to oil the top of the piston and rings, dropped it into 1st rocked it back and broke the piston loose. Kicked it slow again with more oil in the cylinder and moved smoothly. Kicked it over again started up and same thing smoke then piston lock. What could be the reason for it locking up? It's almost like its starving the cylinder of oil. Where should I start to look or is there checks i can do before removing the head?

I know its long but details are key so bare with me. I'm running 85w and a 40:1 mix.

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probably bone dry top end from sitting.the only lube the top end gets is from the oil in the gas. probably needed to squirt a little 2 stroke oil thru the plug hole or take exhaust off and do the same and cycle it thru a few times. time for a new top end now.

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Your could have a head gasket go bad from sitting and its dumping antifreeze into the cylinder and its hyrolocking.

The other possiblity is the crank seal on the oil side is bad and allowing trans oil seep into the lower crank causing the problem..

Best thing right now is to take the pipe off and see what in inside of it.. water, oil or extra gas,, This will also let you see what the piston / cylinder walls look like..

Let us know how you make out..

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i dont think its running long enough to be seizing from lack of oil. he poured oil directly in the plug hole and it locked again, regardless of type of oil it, should have ran without seizing immediately. im with carl, its hydro locking from water, oil or gas. i would pull the plug and turn the bike upside down and give it a few kicks. i bet oil comes out that has collected in the bottom end from sitting.

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I would check for hydro locking too and if that wasn't it I would suspect the lower rod bearing having a flat roller.

Ed

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engines can rust after a year of sitting given the right circumstances. seen it happen especially with castor oil

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you know nothing.... how would castor oil rust an engine??? does it have ?*%@#$% water in it.

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Yeah i used 2 stroke oil with the gas and 85 in the case. I have common sense and pretty mechanically inclined. And I won't need a new top end ill need to get it honed and slap some new rings on it. As far as the hydro locking I can take a look tomorrow but my guess based on the color of the smoke its very possible of water being burnt.

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you know nothing.... how would castor oil rust an engine??? does it have ?*%@#$% water in it.

Castor is an organic plant based oil so it has a high chance of quick breakdown resulting in water left to get on the steel parts

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If its an aluminium bore dont get it honed. I did it to mine and it takes alot of the thin electrofusion plating off the sides making it wear down really fast. But if its steel bore go ahead

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about the hydro locking. once it seizes you can pull the plug and try to spin the engine using the kicker. or put it in gear and rock the bike back and fourth.

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i know its been forever since ive posted here but i havent had time to work on it, i have pulled off the top end and piston and cylinder look good sanded a little to smooth it out and theres no water in the oil so i dont think it was the hg, ordered new ones anyway just need to wait for my new rings to go it, this guy i said he had the same issue on his rm and it was the power valve (think its called) was gummed up with varnesh, so im gonna pull that apart, take the carb apart and soak that, after this ill be clueless cuz itll be a new engine after that

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