Me and my buddy got a 2007 crf250x,im pretty familiar with bikes and very with cars but ive always had 2strokes.Now im working on this bike and it fires up with the choke on  and ill let it warm up and pop the choke off and it dies.Im trying to adjust the carb but i only see what looks like an idle screw but i see no airflow screw.Is there and air adjustment or any ideas why it would stall with choke off?

Also wont fire up with E start relay just rattles so im guessing bad relay or bad battery?

There is no air screw on a 4 stroke carb as such. the fuel screw is underneath the carb bellmouth between the carb body and the rubber boot that goers to the head. It's a bitch to get at and adjust.

My guess is that you probably have intake valve wear and that's why it is not staying running. Check your valve clearances. There is a sticky here that shows you how to do it. My guess is intake valve on right hand side has worn and there is no gap between cam and bucket.

has the bike been sitting long? Sounds like a clogged Pilot jet. Remove and clean if possable. If not they can be had for around $10.00.
As for the Air/fuel screw, the stock screw is a pain to use. Best bet is to buy a "BRASS" aftermarket T-handle screw for around $15 or a flex screw for around $30. DO NOT BUY AN ALUMINUM SCREW.

ok thanks,.i was reading the valve thread already,good info.God theese 4strokes are so compact and hard to work on.

And for the screw i have a flex screw im guessing its mounted on clutchcase side and wraps to to kickstart side.Its weird cause when he brought the bike over that screw was so far out,i dunno on theese but ive always known an idle screw to be 2-3 turns out from closed correct?Also if this helps it bogs when i hit the throttle idling in choke,too me it feels like its not getting gas so maybe ill check the jets like mentioned?

Edited by SNYPER, 21 August 2012 - 07:16 AM.

SNYPER, on 21 August 2012 - 07:12 AM, said:

Generaly the flex screw comes out right next to the idle screw. It should be somewhere around 1-3/4 to 2-1/4 turns out.  It would help if you could tell us where your at with jetting and mods. Jetting for most of these bikes is a 42 pilot and a 150 to 165 main. Has the air box been opened up larger than stock? Has the A/P mod been done? Has the exhaust baffle been modified or an aftermarket system been added? What elevation and temps do you ride in?
I know its a lot of things to check but the more you can tell us the better.
As for the battery, it sounds like its toast. Try and charge it. If you need a new one, go with the 450x battery or equivalent. It will have more cranking amps and will start much better.

Ok so i finnally said F it and took the carb off cause i couldnt see crap in there.And i cleaned all the jets ( i looked at the jet num's and never thought to write em down) im assuming they are all stock and stock needle ( only has 1 notch to clip).But anyways doing this i found the air screw (the flex setup was idle screw) It was dead center of front of carb going through the bowl into carb (i seen a vid and pics were it had a brass twist handle,mine did not it was actually recest into the carb and covered in dirt) Its a basic round peg with 1 flat side as say a stove would have to pop on and off the knob.I used a piece of hose like the carb drains and slid it over the peg which lets me adjust while the carb is on now.Anyways buike fires up and now runs w/o choke on but it got late and still needs tuned some more,has a slight bog when jumping on the throttle  idling.

As for mods ive seen a few in theese forums but i dont think this bike has any,.would cutting the top of the filter box open like ive seen benefit me or the pink wire trick?

Opening the air box will help but you need to drill out the baffle at the same time to get the benefit. More air in and more out. Doing this will lean out your jetting, so you will need to go up on the main size.
Dont mess with the pink wire. That mod only comes into play if/when you swap ot the cam to a Hot Cam or R cam.
The Air/fuel screw on that year is a pain to use on the trail due to the notch you described. Go with one of the aftermarket ones i spoke about. They make it simple to adjust on the fly.
The needle that year sucks because its not adjustable. Go with a 06 or earlier needle or get the JD kit.
The JD kit is your best bet as it comes with pilots, mains, needles and O-rings for the A/P mod. For $70 you will have everything you need to get the jetting where you need it.
Glad you got it running.

Ok so should i not cut the airbox unless i get a new main?And thanks for all the input,great forums^^

Correct. These bikes came jetted lean from the factory. My Ca. model 06 came stock with a 135. Not sure what your stock 07 has. What size will depend on what your starting with and what size you cut your air box to.

If you cut the top of the airbox off it will let more air in, more dirt as well. I made a pre-filter to help keep the bigger stuff out using a frame bent out of 1/4" copper tubing and stretching a $2.00 pair of kids nylon stocking over it. Even after a single ride you can see the benefit of a pre-filter. Check your filter without doing anything and you would notice most of the debris is being filtered from the top of the box where it was cut out. The air will pull in from where there is least resistance so it makes sense that it will come from the top on an opened up box. This does not make full use of the entire air filter. Spread it out a bit, save your air filter, cams and engine and do some type of pre-filter if you cut the top out.

keviwa, on 21 August 2012 - 07:11 AM, said:

I used to have the T-handle fuel screw adjuster and it is still a pain in the a$$ to adjust because the starter motor is so close to it.  In my opinion the only way to go is with the R&D Flex Jet fuel screw.

Ya i seen the T handle on a parts list,.i agree the flex would be the way to go,as of right now i have my homemade flex on it ,its short but works.Just went riding a few days ago and being my 1st ride on this bike,.WOW is all i can say.Just a badass bike all around,runs great and the power is constant.Completely changed my perspective on 4 strokes.Still has a small bog at the bottom of 1st but all this effects is jumping on it from a stop,give it a slight tap to lift rpm's and you can pound it.Can prob use a lil more carb adjust but i was more interested in riding lol.

Cant wait to do some upgrades,Any recomendations for easiest most gain upgrades? Def gonna jet it.