2009 kx250f wont start

Ok guys. New to the four stroke life.

Just picked up an 09' kx250f. Has 27hrs since new. I have had it for about 2 weeks now. Bike ran great. Always started right up. Now i cant get it to start to save my life. Changed out the plug and still nothing. I have spark, its getting fuel and air. Im at a loss. Been trying to get it running for the past three days and nothing. Please help??!

I would check the valve clearences. 

Thats what i am doing tomorrow. I did a leak down and compression test today and everything was golden. I will check the valves and see what is up.

if it has a true 27 hours then it should not be valve clearances , but that is the most common issue of non starting. 


If the valves are out then i doubt it has that amount of hours, even if ridden hard.  

Is the carb clean? Hot start is working properly?.

My 09 gave me troubles after a week of buying it, ended up being a dirty carb and hot start o-ring in the carb that didn't close properly or something like that. since then starts at 1st or second kick

Thank you for all the info. And i believe it is a true 27hrs. I got the bike from a vet rider who used it to follow around his grand kids. Also has a receipt of the hour meter being purchased and put on the bike the same day he bought the bike. I am in the process now of checking the valves and then i am going to pull the carb. Again thank you all

Plug left in silencer? Funny, but common, even among those of us who should know better.

I always start by putting a new spark plug (you already did), then I pulling the carb and checking/cleaning the jets, float bowl, etc... I then reset all "Idle/Air Adjust Screw(s)", have seen those completely off even on low mile/hour bikes. Check and clean any and all "ground points" on the ignition/clutch/neutral lockouts/etc. too if it has any  ;)


Also you could try a few ounces of Berryman B12 in a gallon of fresh gas, it has been known to work some magic on carburetors for several decades now... might give that a try before taking everything apart, it's only 2 or 3$ for a can at your local "China-Mart"  :thumbsup: . I have personally used Berryman Products for over 20 years, great stuff for cleaning out dirty carburetors or injectors.

I pulled the valve cover off and saw tbat it was leaking a little bit. Also pulled the timing covers off and noticed a bit of oil in the stator side. Not sure if four strokes are supposed to have a little oil there or not. Or if my seals are blown. I do get spark though.

You must have oil on the stator side. 


Are the valve clearances in spec ?

Ok, thank you. I know on two strokes if there is oil it means the crank seals are blown.

Intake is at .12mm and exhaust is at .19mm

Ok, thank you. I know on two strokes if there is oil it means the crank seals are blown.

Intake is at .12mm and exhaust is at .19mm

Intake 0.10 to 0.15 and exhaust 0.18 to 0.23 so yours are fine.


Check that the timing is correct, maybe the timing chain jumped a few teeth.  


When you lean the bike over to the side do you get fuel coming out the carb overflow ? 

I checked timing and even re timed the cams just in case. And yes fuel comes out of the over flow when leaned over.

Plug left in silencer? Funny, but common, even among those of us who should know better.

Watched my buddy try and start his crf250 at the track with his plug in and I wasn't going to say a word. About 50 kicks, a gallon of sweat, a few curse words and my sore abs the bike fired up and shot that plug out about 25 ft. I'm glad I was well clear of it, lol.

328, have you tried bump starting it? If that will get it started you can at least see how it runs if it is in fact the jetting. Also, if you don't already have one, pick up a compression tester and see what reading you're getting. probably not the issue, but it could be a good indicator of what's going on in the cylinder.

Edited by 40acres

I have tried bump starting it but still wont fire up. I live on a big hill. My rear end just locks up. Did a compression test and have around 150 psi

Try feathering the clutch in and when you bump start it and give it a LITTLE blip here and there till it fires. Fuel, air, spark.... That's all you need. If the valves are in spec I'm going to revert back to carb related.

Yea im currently tearing back into the carb now.

Put the bike in 2nd when you bump start 

I want to thank everyone for all the help and info. The bike now starts right up first kick every time. I feel like an idiot. The fuel screw spring was stuck in the carb and when i had rebuilt it i had put the new spring in. The old spring wasnt allowing the new one to seat and i was flooding the bike.

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