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2003 RM 250 smoking pistons

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Well guys minion my 3rd rebuild! And the first one was to freshen it up right after I bought her, she ran great right until the piston blew up, prolly had close to 40 hours on it. This last time it went, it may have had 10 hours on it. When the piston blew up the 2nd time, I got it replated and she's till looked new other than having two little scratches in the nikasil so my question is simple, could that have been caused by simply my ring gaps being off? Or is there anther force playing with me?

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Define "blew up"? Broke skirts, chunk-ed a ring, burnt hole in the piston, seized up and so on. How about some photos to help us out. Need more info.

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Well the technical one that's claimed to blow up the piston chipped, I'll postthelink to photobucket here Ina minute

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The top of that piston looks like it got hammered by metal pieces. I think you may have a rod big end bearing going out and throwing junk into your topend. Or just junk from the last time. After three times you should split the cases and make sure everything is perfectly clean. New crank, bearings, seals ect.

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looks like u may be getting some detonation. what gas are u running. did u change the compression?

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looks like u may be getting some detonation. what gas are u running. did u change the compression?

thats what i was thinking

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Hi iv noteced two verticale marks on your barrel in pic 16 that you may have had your piston in the rong way as it looks like your ring has been cought up in the exhaust port. the two line sort of comfirm this as one is lower than the other.

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Hi iv noteced two verticale marks on your barrel in pic 16 that you may have had your piston in the rong way as it looks like your ring has been cought up in the exhaust port. the two line sort of comfirm this as one is lower than the other.

yep, definatly the arrow on the piston was in the carb direction instead of the exhaust like it should have been.

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No sir the arrows where pointing towards exhaust and pump gas 93 octane. With bel ray mc1 mixed 50:1 per their instructions. And rethink its the crank because the bottom rod bearing is notably looser now than it was Wednesday when I rebuilt it last. I.will.know.for sure tonight and i will be sire to take AOL of pictures he he but this bike is going to be the death of.me I'm afraid!!!!

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if it was a cast piston it could have just been a bad casting. it almost looks like the ring caught but that may have happened after the piston failed. if you had higher compression you could get detonation with 93. looks to me that the barrel needs to be replated and hopefully the next rebuild will go better. maybe the pin that keeps the rings from rotating fell out? but that still wouldnt explain the scaring on top of the piston.

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Well its a Wiseco forged stock. And it was replaced after all the pics you see, then I put maybe 15 hours on it and got another piston. The rebuilt it the lactating ans it went before I got a "ride" on it

Well its a Wiseco forged stock. And it was replaced after all the pics you see, then I put maybe 15 hours on it and got another piston. The rebuilt it the lactating ans it went before I got a "ride" on it

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