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YZ 250 2 stroke shuts off out of nowhere resistant to crank/ won't start

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Hello I bought a 2003 YZ 250 2 stroke less than a week ago ?. The guy I bought it off of had just rebuilt the top end and it has a vortex piston. Everything works great for the first 4 hours of riding (which wasn't all at once) started first kick everytime, extremely snappy. Than all at once as I'm backroading with some friends riding down a hill the motor shuts off. I try to roll start it since I'm already cuuising down hill. That just locks up the back tire. Get it to the side of the road and its very resistant to kick. I get it home take the top of the motor off just so I can see the piston head and cylinder wall and everything looks good there. New spark plug. Kicks over but rediciously hard to do so no signs of wanting to start. Please help 

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Are you saying it locked up when you tryd bump starting? was it in first gear ? Then it kicked over hard?  Does it have vforce reeds?  If so I've seen many times where one breaks get stuck in bottom end.  Just did a ktm 65 engine was locked up from it 

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if there's no aluminum streaks on the cylinder then you didn't seize it.

otherwise maybe a crank bearing locked up. I had one lock up so bad it broke loose of where the crankcase pressed on it and gouged the crap out of the cases.

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The back tire locked up when I tried to bump start it in 3rd gear on pavement. I don't know what kind of reeds it has but it will still kick a little it's just EXTREMELY hard to kick and I can't get a full kick. The cylinder wall and the piston look fine

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Is it normal for a crank to sh*t out all at once? The bike ran perfectly up untell  this point

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Just now, Dale357 said:

Is it normal for a crank to sh*t out all at once? The bike ran perfectly up untell  this point

They don't last forever.  Everything goes to the crank first. Antifreeze and oil don't mix could be reason why .rod bearing or crank bearings got hot seize up. See it all the time in engines i do

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Ok thank you for the help everyone. I guess my next question is is there a way around taking it to a shop at $100 an hour labor? I'm not comfortable doing the work myself but I just can't justify giving the local cycle shop $500 or whatever for a couple hours of work. Maybe somebody on Craigslist? Idk if that's safe. I just got into to 2 stroke game and I'd love to start racing this year if I can do it without breaking the bank

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27 minutes ago, Dale357 said:

Ok thank you for the help everyone. I guess my next question is is there a way around taking it to a shop at $100 an hour labor? I'm not comfortable doing the work myself but I just can't justify giving the local cycle shop $500 or whatever for a couple hours of work. Maybe somebody on Craigslist? Idk if that's safe. I just got into to 2 stroke game and I'd love to start racing this year if I can do it without breaking the bank

I have add on craigslist lol but I'm upstate ny 

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On ‎7‎/‎6‎/‎2017 at 8:38 AM, Dale357 said:

Hello I bought a 2003 YZ 250 2 stroke less than a week ago ?. The guy I bought it off of had just rebuilt the top end and it has a vortex piston. Everything works great for the first 4 hours of riding (which wasn't all at once) started first kick everytime, extremely snappy. Than all at once as I'm backroading with some friends riding down a hill the motor shuts off. I try to roll start it since I'm already cuuising down hill. That just locks up the back tire. Get it to the side of the road and its very resistant to kick. I get it home take the top of the motor off just so I can see the piston head and cylinder wall and everything looks good there. New spark plug. Kicks over but rediciously hard to do so no signs of wanting to start. Please help 

depending on how fast you where back roading and how long the downhill was  you may have starved the engine of oil.................extended periods of engine braking  especially if the idle circuit is lean and or you mix the oil light  can spell disaster

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Ok so this is wild. after letting the bike sit for four days or so I decided to try kicking it again because why not? Kicks over just fine now. It even fired but I have the exhaust taken off and it's midnight so I quickly shit it off. I already bought a rebuilt kit online. It's on it's way here now but the bike seems fine now. Any ideas on what could of happened??? And if it will happen again soon?

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okay dale357 this is so weird. cant even believe I came across this post. what happened to ur bike literally just happened to mine! no problems with my bike ever and I'm riding downhill at a decent speed and when I came to a stop the bike shut off. it was slowly shutting off when I reduced speed. I have a 2007 cr85, I thought maybe I blew a piston or something major but what the hell is going on? maybe mine will start up after letting it sit?

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I hope it isn't the piston and just some weird random thing but is that what u were doing? just riding downhill and it shuts off out of nowhere? I also have a 2 stroke. I really hope it isn't the piston or the engine :(

 

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i took the motor apart and the bearing were sheared the crack was bent, the stator bolts were chewed up and the piston was damaged 

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i thought u said 4 days later it started up? as in it was fine?

how much did it cost u to fix everything and get it running good again

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On 2017-07-08 at 3:40 PM, Dale357 said:

Is it normal for a crank to sh*t out all at once? The bike ran perfectly up untell  this point

Could be if it's a wiseco crank. 

Many have had problems with new ones, because you said it's changed? 

Pull of the cylinder and you can feel the rod and the big bearings that holds the crank with your hand, it should be perfect feeling 

Edited by skorpan777

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