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I got a big bike problem i tried to jet my 2002 yz125 and i went to ride it and it had plenty of bottem end. howeever when i went to give it gas it went brrrrrrrrrrrbrrrrrrrrbrrrrrrrr and stailed out. So iwent to start it back up and the kickstart wounldt move so i put it in nietrul to push it home and it wont move. I think its crank bearings and i just got the bike and didnt chech the case oil and i checked it when i got back and the oil was whitish-grey any help is apreshiatied. thanks

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sounds like your piston is fried. Pretty much sounds like you seized it. Pull your plug and start from there. Pretty tough to lock up the bottom end, plus you would have heard alot of noise. Your oil sounds clapped out in the gear box, but as long as it has some kind of lubrication its pretty tough to have the bottom lock up. If you jetted it wrong or F-up on your mix you probably burnt up your rings and piston.

Start from the top and work your way down.

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well, whitish oil means there was water in there. i dont know why it would lock up, my old kx80 did the same thing, but i over heated it, rode it hard for about 40 minutes, wide open racing, on the pipe the whole time, got to hot and expanded to much and locked up. i couldnt kick it or anything, 5 minutes late, i cooled down enough and i could kick it over. have you tried to remove the plug and try kicking it over then? try that, if not it should turn over, even with bad bearings you would just hear a akward noise, like as if there was sand in the bearings. my 95 cr 125 project bike has bad bearings, i can turn the motor over, but it has bad bearings for sure.

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I took out the plug and that didnt work so i took of the head and i can pull the crank up and down with the piston but not with the kickstart. i thought it was a brocken kickstart but if it was my tire would move and mine doesnt

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what does it look like when the piston siezes up

take the top end off and you'll be able to see pretty easily if it's seized. And if it's not seized, then the only price for removing the top is some new gaskets.

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black under the rings means you have blow by, blackspot under the top of the piston but inside it means overheatings, premix burnt to it because the crown was too hot. ash color on the top means over heating and the piston started to melt, scxratch on top of piston and bottom of head means debris got in, may wanna check your needle bearings, piston chipped top ring groove off mean gasket leak, shttered skirt of piston means to much clearence between cylinder wallas and piston, rattle caused a breakage, "scratch, buffed" looking marks on piston means it locked up, called seizure, (four corner, multi-seizure, single point seizure, intake side seizure). a blow out blow hole, hole on top of piston means piston got too hot and melted a hole through the piston.

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well, if you can move it up and down its not siezed, but your piston could still have problems.

are you sure a stick or something didnt get stuck in the brake's or something, because thats what it sounds like. it sounds like your back break locked up when you gave it gas, stalled out the bike, cant kickstart because the sprocket cant move and so on. try putting it in neutral and kickstarting it, if that doesnt work i dont know what to tell you, maybe vapor lock.

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Did you go up or down on the jets? Just the main?if you can move the piston it's not sized! Kick starter gear?

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Well crank turns ("assuming" piston is still connected too crank)so it's not that. Piston goes up and down so it's not that. The only thing connecting the symptons of a locked back wheel and the kickstart is the gearbox and clutch.

Why don't you pull of the clutch cover and check that everything looks O.k on that side. Should be pretty easy to work out why kickstart no longer works. If you take the clutch off completely the gearbox and engine are then independant.

Are you able to turn flywheel or was that my assumption.

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then how do you move the piston up/down with the head off :thumbsup:

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, so its not connected to the rod or crank. it could be the mainbearings , but i dont think it would lock it up, or it didnt to me when my bearings blew. maybe your seals broke and there wasnt enough oil, it must be the crank or something, but i couldnt see the crank locking up because of thsat.

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heres the hole story i got my bike out of the garage i was messing with the airscrew i think it is. then i gave it gas and just putted slow around my front yard in first gear then i was like alright its seems to have alot of bottem end so i took off and it was real slow when the powerband was suppost to kick in so i gave eit more gas to see if it would go and it went brrrrrrrbrrrrrbrrrrr so i tried to keep it from stailing out with the gas and it just locked up the back wheel. so it wouldnt let my kickstart it so i put it in nuetral and pushed it home.my dad took it apart because i didnt want to mess with it he told me the piston moves up and down i figured he meant up and down on the crank but he meant it moves in the head so its not seized. i took a look at it the oil its light grey and the crank wont move any ideas thanks for all the help

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