Hanging idle WITHOUT an air leak??

[tt_four]

So I finally got my bike back together and tried it out last weekend, but I was having the same problems with hanging idle like plenty of people do. I messed with it a while yesterday morning, and pretty much soaked the thing in WD40 before determining that I can't find an air leak anywhere. I pulled my carbs anyway because some gas is drilling from them somewhere, so I'm just going to try to rebuild them, but do you have any good places to start that might be causing this? I don't mind trying these out, but the P.O. installed that god awful loud V&H full system, and I live in the city, so I try to keep the bike running/revving as little as possible when I'm outside my house working on it. Sitting outside revving the engine really isn't my goal as far as staying on the neighbors good side. I guess I'll pull the black caps off the top and inspect that some, I've been wondering if there's a part inside the carb that might stick, keeping the airflow a little longer after I let off the throttle?

Sorry for the repeat question, I know it's been covered so many times, but the answer always seems to be an air leak, and mine could be, but I can't find one!

[lboaman]

I'd be curious to see if you find a solution to this.  I've been fighting the same freaking problem for the past month.  Bike jumps straight to 6K on start.  Sprayed everything with WD40, no effect.  Just finished checking valve clearances, float heights are good, got the little o ring at the top of the carb, no sticking cables; all the usual suspects. 

I have the tank off the bike when I'm running it so I can mess with everything while its revving like crazy.  If I hold my hand over the air filter and restrict the flow, I can get the bike to idle down to 2K, but as soon as I let my hand off, jumps straight back up.

Everything is stock in my case, however awaiting a Buddha jet kit to try and richen her up (don't know if it will help).

Just to check, have you messed with the air/fuel mixture screws? Personally, I've tried everything from 1 turn out to 5 with no significant changes...

[bombjack]

Don't know what they are called in English, but on the carbs, find the rubber caps that you need to remove when you sync the carbs. When you remove these caps your idle will go crazy.
I forgot to put the caps back on when I synced my carb, and I just could'nt get a stable idle. I messed around with this for almost a week before I found out the caps were missing  .
If they are not missing, then check that they are not fractured.

[tt_four]

The little caps that you're talking about, are they the ones on top of the carbs? I have both of those on. I haven't messed with the mix screws. Everyone always says not to touch them, and the bike ran before with them set how they were. I'm just going to try rebuilding them and hope whatever I messed up last time doesn't happen again.

[The Buddha]

Idle can hang with lean mix. This is the biggest cause of the problem.
It also can hang wiht a tight valve or a exhaust leak, neither of which will respond to the wd40 trick.

Cool.
Buddha.

[tt_four]

Hmm... I know all of my valves are tight, but the buckets still spin, so they're not ridiculously tight. I did remove the exhaust to repaint it and replace the exhaust gaskets though, so I'll check and make sure that's on tight. To be honest with you guys, I'm not that crazy about engines.... haha

[ineedanap]

I haven't messed with the mix screws. Everyone always says not to touch them...

Everyone lies.  Touch them.  

The idle mixture is wrong from the factory.  Once you add some mods, it's really wrong.  They're screws for a reason.  That reason is so you can adjust them.

[tt_four]

The brass plugs are no longer there, so the previous owner definitely messed with them at some point, but I don't really trust his work. Is there a certain method to it? Do I screw them all the way in the slowly back them out until it seems to run right, or screw them out and then slowly start screwing them in?

[lboaman]

All the way in, then out as many turns as needed.

[The Buddha]

Hmm... I know all of my valves are tight, but the buckets still spin, so they're not ridiculously tight. I did remove the exhaust to repaint it and replace the exhaust gaskets though, so I'll check and make sure that's on tight. To be honest with you guys, I'm not that crazy about engines.... haha

OK this is the standard buddha trap. There is a potential situation where it is loose enough to spin when cold, and yet tight enough to hang open when warming up but fine when fully warmed up. Think about it. The valve is steel. So is the cam shaft bucket and shim. The head is aluminum which expands almost 2X ... however the head dissipates heat so well, being the only part of these 3 with a live air feed and direct oil puddling.
I'd seriously set em back into the measurable range.

Then ... rejet ... I dunno who says never to touch the air screws ... and we always set it to 3 as a start, not a set in stone number. We also swap pilots ... and mains ... and set the floats and needles.

Cool.
Buddha.

[tt_four]

When you say you set them to 3, do you mean screw them all the way in, then back them out 3 full turns?

I definitely plan on readjusting my valves, I was just hoping to get my bike running so I could ride it to a dealership to get the new shims. I don't really have much 'outside the city' transportation, which is normally fine, but there's no bike shops inside the city either.

The thing that bugs me is that it ran fine before, so I feel like it's something I did wrong putting it back together. It's not like your bike runs ok, you pull it apart, and put it back together and all of a sudden the valves are too far out of adjustment to run properly. First thing I'm going to do is clean and rebuild the carbs, and if it still doesn't run right, I'll start in on some more serious measures, and then I'll be readjusting the valves sometime soon regardless.

[JAY W]

Screw mixture screws all the way in then 2-3 turns out and warm up,adjust to suit.Have you checked your slides and needles are returning smoothly?

[kylegod]

mine did this after dynojet kit, k&n, and slip on cobra f1. set floats, all new o rings and float needles and seats. still hung. dynojets baseline was 2 turns out. Im at about 4.75. Carbs are synched by eyeball pretty damn welll. But im sure a proper vacuum guage would help to get the dialed it. Idles super low for me. 1000rpm somethings 9oosh for a bit. 15 minutes itll stay at its 1250. thinking i need a good synch.

[tt_four]

I have the DJ needles in there now, which I know plenty of people consider to be junk. Would I be better off putting the stock needles back in? and if so, what about the little washers and all that? I haven't gotten to mess with it yet. I'm taking 2 days off this weekend, so I'm gonna try to get some stuff done then. I've also got that box of moped stuff that'll be showing up this week, and even though the GS is cooler, I think the moped will be a lot simpler to get running, so I'll be tempted to get working on that first just so I can at least get out and ride something. It's tough having too many projects all at the same time.

[jp]

One other thing to look at while you have the carbs open. On my 97, the engine wasn't returning to idle when the bike slowed like it should have. Turned out to be the hole in the bottom of one of the carb slides being buggered up. The needle would tilt a little in the emulsion tube and not drop when the slide dropped. I ended up wearing one of the needles to the point it broke, at which point the bike ran like crap since only one cylinder was fully using the main jets. So check the condition of the slides while you have the carbs open to make sure you don't have a similar situation.

[kylegod]

Im going nuts. This is whats happening. I rejetted, new o-rings and float needles. NO air leaks.

It will hold an idle, but not without the rpms hanging and reallly slowly coming down after i rev it. If i turn the idle screw down, the revs wont hang and will come down, but now it wont idle above 1K or will die. Ive been messing with air/fuel screws without much success. Dynojet kit...yeah i know.

So should i keep richening with mix screws until i can set the proper idle without the hanging issue? Im at 5 turns and its still doing it. Plugs look good. If anything a little lean.

Im thinking a good legit carb synch with the mercury sticks will help.

Any ideas?? input? thanks.

[tt_four]

I haven't figured mine out yet. I plan to toy with it a little this weekend, although I'm dogsitting for my parents, so who knows how much free time I'll really have. I've actually spent more time fixing up that moped lately, because because I wanted to feel productive for once. If I get it completely back together and then have 2 vehicles that aren't running right I'm going to blow a blood vessel.

Anyway, I'm gonna mess with mine over the weekend and I'll let you know if I make any progress. If i don't I may up the pilot jet like Buddha recommended for you. My bike has the dynojet kit in it as well. No sure what's so awful about them as it's just different jets and a needle, but who knows. I've been wondering if I'd have better luck if I kept the jets but went back to my stock needles.

[lboaman]

Well, still the same issue here.  Misery loves company.  I have noticed that it seems worse when the bike is fully warmed.  For example, I can maintain a semi steady idle at 1200 with the choke when initially start the bike, but after about 10 minutes of running I can't get the thing under 6K RPMs without restricting the air intake.  Perhaps some hole is expanding as it warms up?

Anyway, I got 125 mains and 40 pilots in yesterday, so I'm going to see how that helps.  I had a dream that it helped, so who knows....

[kylegod]

Ive pretty much narrowed it down to float heights. Doing the check with the float drain and clear tubing, my level is a tad lower than the gasket level where it should be. Such a pain to do because you gotta pull the carbs, then back on, check, then if not right all over again. Erg. And nothing but good weather is on the way. So im gonna just run my idle low and rev it at stop lights to keep it going, haha! Then do float heights on a rainy weekend.

[The Buddha]

Floats can be done on the bike. Heck they can be done wiht the fuel lines still connected ... if you dont mind a little gas spilling here and there and have steady hands, you can get it spot on ... however yo uhad to have swapped out the float bowl bolts with allen head screws.
Cool.
Buddha.