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YZ250F driving me insane!!

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ok guys so ive been taking your suggestions for the past 3 weeks and this bike still will not start. Let me start by saying its a 03 250f that my friend says became "hard to start" which to me meant check valve clearance well there in spec so she wanted the whole thing rebuilt so i put a piston and rings in it... timing is spot on no doubt at all, new plug tried to fire it nothing... so we have a parts bike so just for S#### and giggles i replaced the magento, wiring harness, CDI, and coil and still nothing. it sparks fine a nice blue spark i even sparyed a quick shot of ether in the pug hole and got it to pop once out of the 50 kicks, i cant think of too many other things it could be.... please help haha

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took the bowl off the clean the jets made sure there clean checked the float put it back together but the hot start was broke off but in the off position so should have no bearing on it. replaced it regardless, timing is definitly on cuz i even purposefully set it 180 deg off and turned the motor over by the flywheel and it touched a valve so i put it back and made sure its timed right i just dnt get it man i have the subframe just the carb hooked up to the motor and sparyed a quick shot ether in the plug hole and and got it to backfire once so my concern was maybe its not getting a consistent spark so i replaced all ignition components and still nothing!

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I'd replace the pilot jet, and turn the fuel screw to 2 turns out from all the way in. Might want to change the gas, too if it is old.

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My plan is to take the

Carb off the 08 and see of that works

If so thats the problem

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If not the carb my next thing to look at is valve seats cuz Idk how many hours this bike has and if it's been beat on... Cam timing is spot on I'm not dumb

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i know this is a stupid question, but did you remember the woodruf key when you put the flywheel back on? if not.... theres your problem

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Actually not a stupid question haha cuz I could see someone doing that but yes I did make sure it is back in, thanks buddy

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not trying to be mean but did you put a rag in the intake and not take it out. also i would put good gas in. and make sure the carb itself is getting gas

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Took the head off today and theres a ton of carbon buildup so I stripped the head and am Now polishing everything gna inspect the seats and see what we got

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Ok so I disassembled the head cleaned and buff the valves buffed the entire head and lapped the valves put it together nothing, idk where else to go from here I put a new carb on it as well... Someone please help me

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Ok so I disassembled the head cleaned and buff the valves buffed the entire head and lapped the valves put it together nothing, idk where else to go from here I put a new carb on it as well... Someone please help me

Had the same problem with my CRF. Checked everything!:smirk:

My hot start was stuck open.

Fixed it and now it starts second kick, everytime.

Good Luck!

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why did you replace the top end and check the valves, try to fire it up then take the head back off and clean it? shoulda cleaned it while in the rebuild/ i would check and see if the hot start is stuck somewhere

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It's a new carb buddy that came off a running bike, and we

Didn't have the proper spring compressor but I ended up getting creative and got it done

Still won't start tho I'm gna try to bump start at like 20mph or so in like 3rd and see happens

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