CRF250X Tip: Fuel Screw Installation, Reconnecting The Carburetor Boots

I recently installed a new Sunline Fuel Screw in my 2004 CRF250X. In order to do so, I had to break the carb loose from the airbox-to-carb boot and the carb-to-cylinder boot so that I could turn the carb out toward me to get to the bottom of it. Boots circled below, although airbox-to-carb boot is hidden behind frame.

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First I had to remove the seat, shrouds, tank and fuel line, side panels, muffler mounting bolts, and lower subframe bolts. Then I had to loosen the upper subframe bolt, the airbox-to-carb band screw, and the carb-to-cylinder band bolt. After lifting and rotating the subframe up until the rear fender rested on the tank-or rather, where the tank used to be-I could now break the carb loose from the boots and rotate it.

However, upon finishing the job of installing the fuel screw, I ran into a nightmare of a time getting the carb reconnected to the boots on each side. With the aluminum twin spar frame, there is hardly any room to work and maneuver the carb. I'm ashamed to say it took me 3 times thinking I had it together and then having to tear the bike back apart again to fix it.

The trick that I finally figured out was to take a tiny bit of grease and run it around the inner lip of each boot. This allowed the carb to slip into it with far less effort on my part. It was amazing to me how I could spend so much time trying to get these parts to fit together inside the bike and then just by adding a tiny bit of grease I had them both connected in a couple minutes.

Incidentally, and thankfully, the bike won't start if there's a leak in the carb-to-cylinder boot connection. I'm not sure if this is because the cylinder can't create the suction needed for the venturi in the carb or if it's because all the gas was leaking out through the boot connection, but it helped me determine that there was a problem.



What was the setting you used to set the adjustment screw?

I read in numerous places that 2 1/2 turns out was a good setting, so that's where I started. I just rode it yesterday with the new fuel screw and it was a good start. The problem is that I need to rejet the bike too, so I'll have to do some adjustments later.

All in all, the improvements I made recently really did help with power: fuel screw, cutting the air box, remove the air filter backfire screen, pink wire mod.

Here is the deal.

I have a crf 250 x 2008.

Opened the airbox, new needle 4th position, new 160 jet and I could not get the main jet out of the damn carb, so after fiddling aroun for quite some time I finally relized that my screwdriver damaged the inside of the carb and now their is a peice of metal that prevents me from reaching the Pilot jet (or slow jet)

What should I do can this be fixed, will I need a new carb??



Dom,'s hard to say without seeing exactly what you mean, but before you buy a new carb (which is very expensive), I'd take it to a machinist and see if they can mill out the part you're talking about. Unfortunately, I don't know if I'd be able to give any better advice even with a picture or the carb in my hands.

Good luck.


I have a 2009 crf250x.. Thanks for the advice, but could have used a picture of just exactly where the new fuel mixture screw goes. They sold me one at the dealer and said this would solve my cold starting problem, but no one can tell me exactly how to install it. I thought that just adjusting the pilot jet/screw would enrichen the mixture and help with cold starts with the choke on..???? Does the new after market adjusting screw go in the main jet in the bottom of carb? If so do you leave the big hex bolt looking cover off the bottom of carb after installing the adjusting screw?? Crazy you have to tear the whole darn bike apart to work on the carb. Oh well, any help would be appreciated. (first dirt bike I have had in a long time, love riding, but the hard cold starts are getting old) Thanks, TBrown

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