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2006 YZ250F Starting Problem

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Heard this before?

The bike won't start by kick-starting, has to be be push-started. Seems to perform fine once running.

I checked the valves, had to adjust the right intake by .006in (it was at about .002).

Still doesn't want to start, ugh :D

I've considered tearing apart the carb, but do not have high hopes for that because the bike does not sit for long.

When I kick it over, I am under-impressed by the compression kick-back.

I bought the bike new, it has 80+ hours off moderate motocross. I'm not hitting the rev limiter, but do push the bike hard and ride in dusty conditions.

I can't find any specs on compression or leak-down numbers. Does anybody know of reliable information on this for the YZ250F?

Any other suggestions or ideas?

Thank in advance :worthy: and I'll post details on whatever resolution I find works.

Ride On :)

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i had this problem but i found that turning the idle screw up a bit makes mine crank easy as :) but other than i would take off the carb bowl clean jets and bowl....

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Sounds like it may be a jetting issue if the valves are all in spec. The pilot is most likely off. Have you played with the fuel screw to try to get it right? Don't go by compression through the kick starter, that bike has an automatic compression release mechanism that makes it so the bike has little to no compression when you kick it over to make it easier to start.

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i have a similar problem with my 04 yz250f, once i stall it out on the trail it won't start for the life of me...

any other suggestions? too low octane maybe?

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Typically the #1 reason for hard starting is valves are out of adjustment. Beyond that, it could be a lot of things. I cleaned my carb and it didn't help. I've been out of commission for a while now, but I'm pretty sure my problem related back to a solution stated above which is simply the idle screw needed an adjustment. So somple I didn't think of it :excuseme:

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If you have 80hrs on the motor and havent done a top end yet I know its not cheap but I would do it. I usually replace the top end (Piston and cylinder) at around 50 to 60hrs. Even though the bike does have an automatic decompression mechanism on the exhaust cam you should still get good compression when trying to start it if the piston and cylinder are in good shape. As mentioned already if the valves are in spec and you havent rejetted the bike theres not much else to it. Having to push start the bike and then it runs fine makes me think there is not enough compression to get it going just by kick starting it.

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Oh one last thing. If you decide to do the top end I would suggest getting an oem 08 piston. It bumps the compression from 12.5:1 to 13.5:1 which will give the bike more pop and you dont have to run race gas. Trust me you will feel the difference in how much snappier the bike will be. I do this all the time when building 06-07 engines. You shouldnt have to change the jetting or anything else either. Good luck!

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