I know this has been brought up ad nauseum, but I cannot figure out how to fix my hanging idle.  I'll list what I've done and if there is anything I've forgot please let me know.

1. Replaced boots that go from carbs to engine.
2. Replaced o-rings that are around the "sync" holes.
3. Cleaned the carbs.
4. Adjusted mixture screws (3 turns).
5. Tightened exhaust bolts.
6. Fiddled with the choke (will have to buy new choke cable).
7. Made sure there was slack in the throttle cable.
8. Checked for vacuum leaks.
8. Synced carbs.

I never had this problem before and it just started happening after BaltimoreGS and I rebuilt my engine.  So, I don't know what the hell is wrong and this bike pisses me off.  

if the choke cable is sticking it can cause hanging idle. If your sure thats not it then try turning the idle mix screws out more, running lean can cause this as well.

Quote from: black and silver twin on July 06, 2010, 10:25:06 PM
if the choke cable is sticking it can cause hanging idle. If your sure thats not it then try turning the idle mix screws out more, running lean can cause this as well.

I'm afraid if I bring the screws out anymore they might fall out.  Maybe I'll try 4 turns and see what happens. 

I took the choke cable off when I did my test.

At what rpms does it hang?
When you blip the engine, does it return to idle immediately or is it slowly comming down (like more than 2 secs)?
If it's slow at returning it may be your valves. I've had the same problem. Idle was slowly comming down, and sometimes it got stuck at around 2-3K rpm.

Shouldn't this be solved by the idle screw?  Warm the bike up so your completely off the choke, and adjust the big idle screw between the 2 carb bodies so that your idle is around 1250-1500.  This should solve the hanging idle.

Quote from: ver4 on July 06, 2010, 11:06:35 PM

Quote from: black and silver twin on July 06, 2010, 10:25:06 PM
if the choke cable is sticking it can cause hanging idle. If your sure thats not it then try turning the idle mix screws out more, running lean can cause this as well.

I'm afraid if I bring the screws out anymore they might fall out.  Maybe I'll try 4 turns and see what happens. 

I took the choke cable off when I did my test.

did you make sure the choke plungers were in all the way? even with the cable off the plungers may be stuck open.

the screws wont fall out unless you go more than 4 turns, ive been running my screws at 3.75 turns for 2 years and they havent moved.

Quote from: utgunslinger13 on July 07, 2010, 07:45:14 AM
Shouldn't this be solved by the idle screw?  Warm the bike up so your completely off the choke, and adjust the big idle screw between the 2 carb bodies so that your idle is around 1250-1500.  This should solve the hanging idle.

if the engine is running too lean the rpms wont be solid and will vary wildly, so to "fix" it some people just up the idle. when the idle is upped it opens the butterfly valves more which causes lower vacuum when you let off the throttle which can cause the idle to fall slowly. the remedy is to set the idle mix to a point where it idles solid so the idle can be set lower (1100-1200rpm when hot). with the mix set properly it should idle smooth at 1100, there is no need to set the idle above 1300. upping the idle will only worsen the problem.

Quote from: bombjack on July 06, 2010, 11:40:29 PM
At what rpms does it hang?
When you blip the engine, does it return to idle immediately or is it slowly comming down (like more than 2 secs)?
If it's slow at returning it may be your valves. I've had the same problem. Idle was slowly comming down, and sometimes it got stuck at around 2-3K rpm.

could be valves as well, when were they last checked?

do one thing at a time.
1. check choke plungers
2. turn mix screws out more, then readjust idle to 1200 when hot.
3. if neither 1 nor 2 fixes/improves it, then check the valves.

Valves were checked when engine was rebuilt and they are spot on.

Everything inside the carbs seem to open and close appropriately. 

I still have to go out one more turn with the mixture screws, but it's way too hot to do that right now.

The idle hangs at 3K RPM (when hot).  When it's not hot, the RPMs do drop, but they come down slowly.

float heights?

Quote from: pandymai on July 07, 2010, 11:00:16 AM
float heights?

That's the only thing I don't know how to check.

Quote from: ver4 on July 07, 2010, 11:35:24 AM

Quote from: pandymai on July 07, 2010, 11:00:16 AM
float heights?

That's the only thing I don't know how to check.

http://www.gstwin.com/float_height_check.htm

how to adjust is based on your personal preference. you can either take the carbs out or just adjust with them on the bike as long as youre careful to drain the gas and work in a tight space to bend the tab in the correct direction. i did my correction on bike and it wasnt that hard.

you could also try tapping the carbs and if that changes anything than maybe it's stuck floats

I had this problem for a while, and tried everything to fix it. I think the biggest help was turning down the idle. the thing that took me so long to catch it is that it was already set at 1200rpm and was still hanging, so I figured that couldn't have been the problem. At 1200 rpm it would hang about 3-4k if I revved it that high, so while it was there I would turn out the idle adjust screw until it dropped. I would then rev it again and it would stick a little again, so I'd turn down the idle again and keep doing that until it was still set at 1200 and it wouldn't hang. I don't know why it could be at 1200 and hang, but I could also turn down the idle a lot and it would stay at 1200.

My RPMs go down now but they do drop slower than i think they should, plus it doesn't always idle perfectly smooth. I know my valves are tight though so I'll see how it feels after I get to adjust them.

Changed out the carbs, but I'm still having the hanging idle.  Next step will be to check valve clearance, again. 

tt_four:  BaltimoreGS and I tried your method, but the bike wants to die with the idle set too low.

Quote from: ver4 on July 07, 2010, 04:31:24 PM
Changed out the carbs, but I'm still having the hanging idle.  Next step will be to check valve clearance, again. 

tt_four:  BaltimoreGS and I tried your method, but the bike wants to die with the idle set too low.

do you mean adjusted the carbs?
also I forgot to mention carb sync.

I feel your pain I wne through this recently...did the same thing kept messing with the idle screw....cleaned the carbs checked the float height etc...the only thing I didn't do was check the valves. Was making me crazy...Finally I just stopped messing with it and it seemed to fix itself. I know this is no help to you but I think I was chasing my tail by constantly adjusting the idle....The engine really does need to be hot to adjust it properly. I also added a little Marvel mystery oil to the tank....don't know if that made a difference.

Good Luck

Quote from: black and silver twin on July 07, 2010, 09:52:55 PM

Quote from: ver4 on July 07, 2010, 04:31:24 PM
Changed out the carbs, but I'm still having the hanging idle.  Next step will be to check valve clearance, again.  

tt_four:  BaltimoreGS and I tried your method, but the bike wants to die with the idle set too low.

do you mean adjusted the carbs?
also I forgot to mention carb sync.

No, we changed out the carbs to eliminate them as the problem.  Of course we could have two sets of defunct carbs.

Also, in my original post, I mentioned that the carbs had been synced.

Quote from: ver4 on July 08, 2010, 09:02:13 AM

Quote from: black and silver twin on July 07, 2010, 09:52:55 PM

Quote from: ver4 on July 07, 2010, 04:31:24 PM
Changed out the carbs, but I'm still having the hanging idle.  Next step will be to check valve clearance, again.  

tt_four:  BaltimoreGS and I tried your method, but the bike wants to die with the idle set too low.

do you mean adjusted the carbs?
also I forgot to mention carb sync.

No, we changed out the carbs to eliminate them as the problem.  Of course we could have two sets of defunct carbs.

Also, in my original post, I mentioned that the carbs had been synced.

What jets are in the "new" carbs? same as "old" carbs?

When the bike initially gets warm-to-hot is one exhaust downpipe initially hotter than the other?

Hanging is a lean condition... usually... if you swapped out carbs and have the exact  same problem- check your vacuum line to the petcock, make sure your new intakes are tight and came with O-rings (should have...they're usually already wedged in the groove for you..).

Make sure your carb top orings are in there (they can be displaced easily..). Also make sure your throttle cable is not binding up and is routed correctly.

Go over the carbs you have out now and check to make sure they are both clean... Check the pilots etc and all the little passages.. You can have the carbs "perfect" and some crud left in the fuel lines will get right back in there to clog something up...(especially if the thing sat for a while..)... Ask me how I know.

Never switched out the jets.

  sorry to break in on the post but i read something about air/fuel mixture screw. i know where the idle screw is between the carbs. is this one in the same? or is there a different one i need to look for? 

Quote from: importslife on July 10, 2010, 12:13:23 PM
sorry to break in on the post but i read something about air/fuel mixture screw. i know where the idle screw is between the carbs. is this one in the same? or is there a different one i need to look for? 

Different screw.

I believe the air/fuel mixture screws are located under a brass cap that is near one of the carb brackets.