02 250f help needed

Ok 250f guru's-

I have a 2002 250f since brand new. Just replaced the clutch and did the valves recently. Decided to throw the Dr D pipe on it I had sitting around as well. Since I put the pipe on, the bike is a little different. It seems to still give a little gas even after I stop giving it throttle. Ex, if at an idle, and I blip the throttle some, it takes a couple seconds, maybe 2-3, for the rpms to come back down even though the throttle is back to the stop. Or if Im riding harescrambles, or just riding, coming up to a turn in which I let off the throttle, iit still goes for 2 seconds. What do I have to adjust to get the bike back to normal.

Thanks,

Joe

Mixture screw underneath the carburator.

Throttle could be sticking a bit, clean the card, and the spray the throttle cable at the top and the bottom of it.

That is the simplest problem it could be if not, throttle mix, and any other suggestions others may have.

Sounds like it's possibly a fuel mixture problem. It's not engine braking becuase of a rich or lean misture....rich I would think but that goes against the fact that most people step up the main jet on thier bike a size or two when a better pipe is installed. If you're too rich you're motor tends to decelerate slower, giving you less engine braking. If it's lean, the opposite happens.

Hanging idles are commonly caused by a too-lean condition. If you can't correct the problem by adjusting the fuel screw within the normal range of 1-2 turns out, look for either an air leak between the carb and engine, or tight intake valves.

Finding none of that, go back to the fuel screw and see if it will begin to act normally between 2 and 3 turns out. If it does, go up one on the pilot jet and try again.

Hanging idles are commonly caused by a too-lean condition. If you can't correct the problem by adjusting the fuel screw within the normal range of 1-2 turns out, look for either an air leak between the carb and engine, or tight intake valves.

Finding none of that, go back to the fuel screw and see if it will begin to act normally between 2 and 3 turns out. If it does, go up one on the pilot jet and try again.

I lost my service manual in my mess of a garage. Which screw are you mentioning? Its not the one with the nice handy black knob, right? Im assuming I need a screwdriver, but which screw. I never had to worry about it, it has run great since new. The dr. d made it run different, although they state the bike would need no jetting or changes if it ran fine before the pipe addition. Yea right.

I raced 2 harscrambles with the bike like this, for a total of 4 hours of hard riding, any damage from doing so?

Thanks

Follow grayracer513's advice.

Look at ThumperFAQ Fuel Screw for the location of the fuel screw. Other links on this site will tell you a LOT about your bike, go to http://www.thumperfaq.com

The black knob screw adjusts the idle speed, which should be between 1900-2100 RPM.

The fuel screw will probably cure the hanging idle, if not 1 size up on the pilot WILL, with the combination of the fuel screw being between 1 1/2 and 2 turns out.

You have not likely done any damage to your engine. :naughty:

Download a service manual at http://www.thumperfaq.com/oemmanuals.htm

The problem you are experiencing is called "hanging idle", and like everyone else says, it is usually caused by a lean condition. Richening the fuel screw (turning it outwards) in 1/4 turn increments will generally fix the problem. You can search for "hanging idle" and probably get a weeks worth of reading.

Here's a great fuel screw link.

http://www.thumperfaq.com/fuel_screw.htm

Seat the screw gently(!), while counting the turns (inward) to figure out where you're starting at, then open it back to where you started. Then adjust it outwards testing to see if the idle comes back down (having the bike warmed up is best). If you get beyond 3 turns from fully seated, then go up one size on your pilot jet and re-set the fuel screw to 1/2 turn open, and start tweaking again.

If this doesn't fix it then you may have a frayed throttle cable, or a sticky throttle tube. It's usually a lean problem though, like your fuel screw or an air leak in the intake. Check for leaks by squirting starting fluid at the intake joints with the motor running. If it speeds up, you've found the leak.

Also, I'd be surprised if your new pipe wouldn't work a lot better with a step or two richer main jet. They're easy to change and should really help you get the most out of that pipe.

Check the rubber boot between the carb and the head. Sometimes the backpressure will try to blow the carb off and on my sons it actually tore the boot. If that is it replace the boot and install zip ties around the carb and top motor mounts to keep the carb in place. I suggest the zip ties as a preventative either way.

Probably a stupid question, do you need to remove the carb to access the fuel screw if you don't have one of those aftermarket ones?

losen the carb boot clamps and then rotate the carb so you can get a short flat bladed screw driver in the hole. Dont forget to tighten the clamps back.

Thanks!

If you have one of those screwdrivers that has interchangeble bits you can use one of those bits to get to the screw. The screw is difficult to get to but you need to have the carb on so that you can adjust it while running. Did you check the boot that I was talking about?

After reading this thread yesterday i adjusted my fuel screw because i was having the same problem.......My fuel screw is now three turns out but it cured the problem completely. No more hanging idle and it idles smooth now. The hanging idle was really giving me a hard time in tight berms and corners......Is three turns out too much? It works so good now I dont really wanna change the pilot if I dont need to.

If it's running OK at three turns then you can probably leave it there, but when the weather cools off, you'll be too lean again. I'd have a one-step-larger pilot jet on hand, so you can make the change over. You might want to try it out anyway, to see if it runs any better.

Also check once in a while that it's staying at three turns out. If you de-compress the spring that's in there enough, the fuel screw could vibrate out. :naughty:

Before you start "screwing" with the fuel and the carb, why don't you check to see that your throttle cables are lubricated and running smoothly and make shure that they're not worn! Lube your throttle tube too.

Then if OK go crazy changing fuel settings!

my throttle cable is/was fine....snaps back imediatley.......I was sure it was an adjustment change that was needed. Im meticulous about a smooth throttle tube/cable to avoid a WOT stick....been there...No fun.

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