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Help YZ250F 2001

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hi,

i bought a YZ250f last week the guy i bought it off said he was having trouble starting it but being a mechanic (diesel) i figured it wont be anything too taxing to repair,

got it home and changed the spark plug (he had the wrong one in there) and after about 4 kicks it started and seemed to run pretty well, then i noticed a small amount of coolant coming from the front of the engine (head gasket) so i ordered a new gasket from Yamaha and replaced it no worries.

now i cant get the bloody thing to start.

checked and reshimmed the valve clearences they wernt too bad only slightly out of range but i figured may aswell do them anyway and still the thing wont start.

im out of ideas now,

i have plenty of compression there is fuel getting into the engine as i checked the spark plug and it was wet, i also checked there is spark which there is so now i am out of ideas.

rechecked engine timing and is spot on rechecked valve clearences and they are all good

HELP

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if the motor has been completely taken apart it can take 50+ kicks to bring it to life the 1st time.

a good ol' shot of engine start in the air filter can reduce that number by a lot.

oh and on the 01, make sure the plug wire is firmly into the plug cap, they can come out.

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cheers for the reply,

how about carb settings ?? i.e factory settings any ideas ?

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I also use to struggle to start my bike, and I would resort to push starting down a slope more often than not. I eventually sent it for a dyno and a new needle jet did the trick.

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These carbs won't start easily unless jetted right so if the spark, timing, valves and compression are good it suggests the carb is blocked or jetted wrong.

Edited by Barra8

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definately not 180 out. i on the crank and cams show E-I E-I and dots line up. worst thing is it ran before i changed the gasket.

i have cleaned the carb out the FU***NG thing wont fire

HELP

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if the motor has been completely taken apart it can take 50+ kicks to bring it to life the 1st time.

a good ol' shot of engine start in the air filter can reduce that number by a lot.

oh and on the 01, make sure the plug wire is firmly into the plug cap, they can come out.

Sorry, but slightly side discussion.... why the 50 kicks thing? Not questioning the comment, as I am questioning the why this would happen. Seems like if everything is right, it should start easily after a fresh motor ( i know not fresh in this case).

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the bike ran before you tore it apart so you know the carb will work 'I wouldn't mess with the carb'

until you figure out what is wrong

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maybe was the wrong thing to do, but i took the carb apart cleaned the jets however the float seemed to be set wrong so i adjusted it a little bit, however i may have done it wrong can anyone give me a point in the right direction for adjusting the float and screw on the bottom of the carb, i have had a couple of back fires but just wont fire up :(

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Edited by barra8 to stop misinformation. I got a little confused and said it may be 180 degrees out. lol.

Edited by Barra8

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Remove cams, turn crankshaft counterclockwise one revelution until the ''I'' mark on the rotor is aligned with stationary pointer. Now refit the cams as mentioned above.

To see how this has already helps someone with this problem see thread below (not a 250 but same, same other than yours is YZ cams/timing )...

http://www.thumperta...g-timing-issue/

Edited by Barra8

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To me this seems like the rubber carb boot between the head and carb is not right... loose/cracked. I would check that. Also since youre a diesel mechanic I just have to throw it out there that the common valve lash measure tools you get from an auto store are all too large. It took me quite a while to realize this. Fortunately I didn't set my valves up before noticing. You need .004, .005, .006 and .008. inches.

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ok just rechecked my valves and one exhaust valve is out its showing 0.15mm and it should be between 0.17-0.22mm would this stop it from starting ?

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ok just rechecked my valves and one exhaust valve is out its showing 0.15mm and it should be between 0.17-0.22mm would this stop it from starting ?

It suggests that you may need to replace the valves soon but it should at least start.

Edited by Barra8

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That's enough clearance for it to start anyhow. Do you know the starting drill for the older bikes without the automatic decompression cams?

1- Push down on the kickstart lever until major resistance is felt. This puts the piston near TDC

2- Pull in decompression lever, and move kickstart lever about an inch. This gets the motor slightly past TDC

3- Release decompression lever, return kickstart lever to the fully upright position, remove hand from twist throttle (place it on brake reservoir)

4- Give it one full kick!

This routine must be followed for the older machines to start reliably. If the engine is cold, use the choke knob and twist the throttle twice before using the starting drill. If the engine is hot, use the hot start lever/knob before using the starting drill. But in all cases, the starting drill must be followed.

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hi everyone thanks for all your help finally got her going although when i twist the throttle it revs as normal but then takes ages to come back down to idle and ideas ?

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