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Just Picked Up 02 Yz250f

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Hey everyone, I just picked up an 02 yz250f in need of some work. I enjoy working on bikes as a hobbie but am used to 2 strokes. Anyway the guy said he didnt know why it wouldnt start then when i checked the oil he said o theres no oil the guy drained it to check what was wrong. so i asked what was wrong and he said something like the cam was bad so it messed up the valves because of his weight(275lbs). I dont see the relevance of his weight so i dont know if the guy just didnt know what he was talking about or what. Anyway i cleaned the carb which im sure needs to be adjusted still, found a jet clogged and put a new plug and fresh gas but still wont start. Im gonna check the valves soon but have to wait for a shim kit. Meantime i dont know if its not starting because of the valves or if its just because these things are hard to start. any advice? thanks and sorry for the long story

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If the bike has been sitting awhile, it's probably got a bunch of half-dried fuel in the carb and tank. I think I would start there. Clean all the old fuel out of everything and give the carb a good cleaning. While you have the carb off, check the valves and put in a new plug too.

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If the bike has been sitting awhile, it's probably got a bunch of half-dried fuel in the carb and tank. I think I would start there. Clean all the old fuel out of everything and give the carb a good cleaning. While you have the carb off, check the valves and put in a new plug too.

as i said above I put fresh gas in tank, cleaned the carb and the clogged jet, and put a new plug in

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Does it have good spark? Yes? Then check cam timing and fuel delivery system.

No spark? Check all connections then refer to manual for troubleshooting tree of stator and CDI.

As far as fuel delivery system these bikes are very tempromental to junky gas. Was it the pilot jet that you replaced? You really need to go thru every passageway with carb cleaner and compressed air. The ethenol in today's fuel gums stuff up really bad.

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Does it have good spark? Yes? Then check cam timing and fuel delivery system.

No spark? Check all connections then refer to manual for troubleshooting tree of stator and CDI.

As far as fuel delivery system these bikes are very tempromental to junky gas. Was it the pilot jet that you replaced? You really need to go thru every passageway with carb cleaner and compressed air. The ethenol in today's fuel gums stuff up really bad.

It has spark.. i cleaned the carb and yes it was the pilot jet that was clogged. also i noticed that where you put the screw driver to tighten the pilot jet the piece was broke off. it was broke above the hole though so it didnt make the hole bigger. everything else was cleaned though. here is a pic of my cams, it seems like enough links(13) but looks like the dots dont line up like the right one is a lil higher, is this normal?

112.jpg

110.jpg

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as i said above I put fresh gas in tank, cleaned the carb and the clogged jet, and put a new plug in

Yup, I'm retarded.:bonk:

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Your timing is off by one tooth. The YZ should have 12 cam chain pins between the punch marks.. The WR has 13 but a common mod is to make it YZ timing. The cam timing being off 1 tooth like that shouldn't stop it from starting though.

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ok so i just checked the clearance from my feeler gauge and the exhaust was more than .152 and less than .203 so i guess that would be in spec range? intake valves i couldnt get a .076 to fit in so thats obviously way to tight. would the above marks not lining up affect the reading? is there anythings else to check besides the marks to see that its ready to check the clearance?

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Your timing is off by one tooth. The YZ should have 12 cam chain pins between the punch marks.. The WR has 13 but a common mod is to make it YZ timing. The cam timing being off 1 tooth like that shouldn't stop it from starting though.

how would i get it back to 12? take the cam off and spin it a tooth?

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sorry to keep posting before any replies, i checked the intake valve again and from the kickstarter side the furthest intake valve seems to be pretty close to spec, the middle one i cant check because my feeler gauge is too wide to fit in there but the one closest to the kickstarter on the intake side the bucket rubs the cam and as i slowly turn the crank i can hear it rubbing and the bucket actaully spins clockwise as i spin the crankshaft. does this make sense? i dont think its supposed to but would that stop it from starting?

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Tight valve clearance would make it hard to start cold. Need to get a feeler gauge that is narrow enough to fit in there. Yes to fix that cam timing you relax the tension on the cam chain tensioner, unbolt intake cam and rotate the cam counter clockwise one tooth

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Tight valve clearance would make it hard to start cold. Need to get a feeler gauge that is narrow enough to fit in there. Yes to fix that cam timing you relax the tension on the cam chain tensioner, unbolt intake cam and rotate the cam counter clockwise one tooth

can i bump start it to see if itll run? or should i wait to fix the valve? also if i put new shim on the one valve should i do all new shims on all valves?

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12 pins between the dots. If you're going to do one valve you might as well do all at the same time.

Ah crap man my bad!!! I miss counted, your timing is correct. Sorry about that!!L

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12 pins between the dots. If you're going to do one valve you might as well do all at the same time.

Ah crap man my bad!!! I miss counted, your timing is correct. Sorry about that!!L

well thats good to know.haha. back to the valves i was gonna get the shim kit but if the other valves are in spec do i just put the same size shim in it? and i would put a smaller shim in the tight valve right? sorry for all the questions, these 4 strokes have waaayyy more to em than a 2 stroke.

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If they are in spec you don't even have to remove the buckets when you take the cam out, just leave them. The one that is out of spec, if out of spec, remove the cam then the bucket and yes go to a smaller size shim.

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If they are in spec you don't even have to remove the buckets when you take the cam out, just leave them. The one that is out of spec, if out of spec, remove the cam then the bucket and yes go to a smaller size shim.

Ok ill order a shim kit and let you all know the outcome and thanks for all the help. Im sure ill be asking more questions.haha

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I had the same issue, your timing chain is probly stretched and needs to be replaced, cheap fix, 20 bucks at your local yamaha dealer. Check your chain slides while you are in their.

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