Hanging Idle, I'm stumped

[lomitamike]

2001 WR 426 with a severe case of hanging idle. I've taken my carb apart 3 times ( all jets, needle. AC pump, hot and cold chokes, pilot screw, slide plate. float with little rubber plumb bob ). The only thing I have'nt taken apart is the air cut valve. I've sprayed carb cleaner everywhere dried with compresed air reassembled and still, hanging idle. Checked slide plate with magnifiying glass and it looks fine. There is a couple of very tiny cracks in rubber carb joint in the normal places near the small protrusions where the metal tab fits in between ( probabley from loosing clamps and rotating the carb so many times for adjustments). But the carb joint does'nt have any noticable cracks.

Any suggestions / recommendations would be greatly appreciated.

Maybe someone knows the correct process of elimination that will be the most cost effective.

Thanks; Mike

[the426master]

what do you mean hanging idle is it staying reved up try backing the air screw out a couple of turns

[Matty05]

Hanging idle usually means lean pilot circuit!

As long as the cracks aren't leaking any air, go bigger on the pilot jet if adjusting the fuel screw out does not help.

[PBDBLUE]

Usually means a very lean pilot but one other possibility. The slide plate (the black flat plate on the engine side of the slide) can go in two ways. The side with the cutaway faces the bottom of the slide but it will fit in with the cutaway up which causes all kinds of weird idle problems. Don't ask how I know!

[ncampion]

One other possibility, corrosion in the idle passages in the carb body. Happened to mine, no good fix. Water gets in from washing or water crossings. Finally replaced carb with an Edelbrock, best thing I ever did for the bike.

[Yamaster]

Sounds either like a lean pilot circuit like matty said or maybe an air leak.

[Matty05]

Usually means a very lean pilot but one other possibility. The slide plate (the black flat plate on the engine side of the slide) can go in two ways. The side with the cutaway faces the bottom of the slide but it will fit in with the cutaway up which causes all kinds of weird idle problems. Don't ask how I know!

It has caught me out before! It will backfire really bad if the vacuum plate is up side down, so I guess you can count that out. With the vacuum plate upside down, I tuned it right with a 52 pilot jet, still needed bigger, with it the right way around, 48 pilot was needed.

[slipper40]

Just a Quick one guys i had a similar problem to this the revs would hang for a couple seconds just off the idle and return when blipped, i checked the lot cable's ,throttle sleeve, carb, carb slide,and found nothing in the end i found the problem when i laid the bike on it's side to clean the bottom of the bike all the vent tubes from the carb were either blocked or partially blocked. I cleaned em out and the problem went away

[lomitamike]

Thanks for all suggestions. The hanging idle I'm experienceing is the RPMs staying at about 1/3 throttle when throttle is closed. It happens at start-up and after I blip the throttle. Sometimes it will usually last for minutes sometimes seconds. If I turn down the idle screw RPMs drop to normal but then I have to quickly turn idle screw back to previous spot so it doesn't stall. I just installed a ZipTy screw so I will play around with the pilot circuit for starters.

One other pilot jet question? If you have a lean condition at idle, lean means to much air, right? So if you go from a 48 to a 50 would that be adding more air? Or do the larger numbers mean smaller openings?

Oh yeh, has anybody had idle problems due to the rubber ring between the slide and the slide plate?

Thanks; Mike.

Currently running a OBELN needle #3 clip, 168 main, 48 pilot, 100 pilot air, 200 main air. Ran great until I let it sit for about 6 months.

[450high]

Check that your decompression cable isn't tight around the frame especially when you turn the bars.I had this problem and it took foreever to find.I would check the whole decompression lever,cable curcuit.When it faults try pulling in the decompression lever and if doesn't raise the revs any more it is probably to do with the decom system.

[Dodjy]

One other pilot jet question? If you have a lean condition at idle, lean means to much air, right? So if you go from a 48 to a 50 would that be adding more air? Or do the larger numbers mean smaller openings?

Currently running a OBELN needle #3 clip, 168 main, 48 pilot, 100 pilot air, 200 main air. Ran great until I let it sit for about 6 months.

The bigger number means more fuel - richer. If it's happening since sitting around for a while could be gummed up pilot jet. You really need to clean all the jets out really well, poke wire through etc as you can't see blocked jets sometimes. Hanging idle usually comes from you raising the idle speed adjuster off the pilot circuit due to a lean pilot mixture (as the others said). In other words your using the slide to control your idle instead of the pilot circuit. Once you do this you loose control of the idle and it will keep hanging or stall on you. Check your jets are clean and you have no air leaks between the carby and your motor. I would have thought a 48 pilot is OK, especially if the bike ran well before.

[Paewraul]

Yeah, I know... old post but good for reference.

Check your carb slide. I bet it's in upside-down.