timerider Posted March 31, 2008 Report Share Posted March 31, 2008 I hope someone can help me here, i have a 99 txt 250 which i have just bought recently, it was a real mess when i got it and i have just finished sorting it out, i have stripped everything and cleaned it up ( new air filter, fresh fuel, cleaned all pipes and filters and new oil) and i have put it all back together.when i kicked it over it started second kick no problem but now it is seems to be revving a bit too fast on tick over and very fast with the choke on, although i didn`t adjust anything while it was stripped. Could this be because it had been adjusted before hand when the bike had a dirty air filter and clogged-up fuel filters ? Will i have to re-adjust the carb now that everything is new and clean ? and if so can anyone suggest how to set the fuel and airscrews. Thanks in advance for any advice. Quote Link to comment Share on other sites More sharing options...
gasgas4life Posted March 31, 2008 Report Share Posted March 31, 2008 hi, bikes always run fast on choke thats what they do. When off choke and still running fast turn the tickover screw down (anti-clockwise) it should sort the problem Quote Link to comment Share on other sites More sharing options...
jse Posted March 31, 2008 Report Share Posted March 31, 2008 I hope someone can help me here, i have a 99 txt 250 which i have just bought recently, it was a real mess when i got it and i have just finished sorting it out, i have stripped everything and cleaned it up ( new air filter, fresh fuel, cleaned all pipes and filters and new oil) and i have put it all back together.when i kicked it over it started second kick no problem but now it is seems to be revving a bit too fast on tick over and very fast with the choke on, although i didn`t adjust anything while it was stripped. Could this be because it had been adjusted before hand when the bike had a dirty air filter and clogged-up fuel filters ? Will i have to re-adjust the carb now that everything is new and clean ? and if so can anyone suggest how to set the fuel and airscrews. Thanks in advance for any advice. Having to adjust the carb after doing what you describe sounds "normal" and it's a fairly easy process. When weather conditions change a fair amount, you'll probably want to do it again now and then, just to keep the throttle response sharp. I think you have the PHBL Dellorto on your bike, which has a fuel screw for adjustment, but just to be sure (I've seen carbs substituted so it's always good just to check to be sure) look at the side of the carb and you'll see two adjustments. The one in the center of the carb body (it usually has a knurled knob) is the idle speed screw and turning that in or out mechanically raises or lowers the slide slightly to control the tickover speed. I usually set my idle with the engine warm, bike in gear and clutch pulled in to the normal point I would use for disengagement when in a section, for instance. This way my idle speed in normal operation would be high enough that stalling is avoided. The other screw on your carb is probably to the Left of the knurled center idle-speed screw (closest to the manifold/cylinder) and that's a fuel adjustment. I adjust mine with the engine warmed up and in Neutral, by blipping the throttle quickly from idle and turning that fuel screw in or out slightly (maybe 1/8th of a turn each time) until I get the best throttle response. Carbs with an air adjustment screw (like the PWK28 Keihin on the Raga) have the adjustment screw to the Right on the idle speed screw (nearer the air box) but the proceedure is essentially the same. The difference between them is which way they are turned to, for instance, lean out the mixture. A fuel screw is turned "in" (clockwise) to lean out the mixture as it would be decreasing the amount of fuel in the air/fuel ratio and an air screw is turned "out" (counterclockwise) as it would be increasing the amount of air in the ratio, both of which would result in leaning out the mixture. Jeez. I made that sound complicated, didn't I, but the actual process is simple. I added the explanation because I always like to know what's really going on when I do an adjustment, rather than just how to do the adjustment. Jon Quote Link to comment Share on other sites More sharing options...
timerider Posted March 31, 2008 Author Report Share Posted March 31, 2008 Cheers for the excellent advice guys, i have followed your instructions and the bike is now idling much better and the throttle response is great. I have been away from bikes for quite a while now and it`s been great sorting out this very rough bike, i`ve replaced the wheel bearings, headset bearings and fork seals, the only problem i have now is a little bit of clutch drag, i have changed the gearbox oil with ATF Dexron 3 as apparently this is what gas gas recommend, and the clutch works much smoother now but the drag is still there. Any advice on this would be greatly appreciated. Keep giving the good advice guys because without it, us people without a clue would be well stuck. Cheers again. John. Quote Link to comment Share on other sites More sharing options...
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