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idle/pilot guidance please(hanging idle, black out tailpipes)

  • Thread starter Thread starter Zero260
  • Start date Start date
Z

Zero260

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Let me start with the details. 81 suzuki GS850G, factory everything except mac 4-2 pipes put on by PO, and aftermarket non-vacuum fuel petcock. factory jets. carbs dipped. new o-rings, pilot plugs, float needles, slides are good. new manifold and air box boots and clamps. air box resealed. k&n air filter lightly oiled. valves clearances are good. coil relay mod, and new caps. I;m probably forgetting something, but I believe I have refreshed everything I can think of.

On to the problem. I am having a hanging idle. When I blip the throttle it hangs at 2-3k for a few seconds, sometimes longer and then settles down, but doesn't idle smooth. I have the pilot screws set at 2 1/4 turns. any more in and it hangs more, any more out and it produces black smoke out the exhaust and bogs down. it rides fine but when cruising at 1/4 throttle or less, sometimes it burbles a bit. seems to run fine at all other levels of throttle. I did plug chops at 1/4 and idle and both are black and sooty. 1/4 throttle seems to be slightly less sooty than Idle. also it starts with no choke and bogs down with choke on at all.

I'm beginning to feel I'm grasping at straws. I need some help getting pointed in the right direction. What else could be causing it? I'm almost to the point of getting another set of known good carbs to switch for mine, but with my luck it will stay the same
 
Seems likely that you also replaced the o-rings at the carb boot/head interface so...... Maybe the enricher circuit is not shutting off , do the plungers appear to retract fully when "choke" is off?

edit. This stuff bothers me.....
."......also it starts with no choke and bogs down with choke on "
 
Last edited:
Sounds like too much fuel through the pilot circuit.
What did the rubber plugs look like? Tight or loose? You remembered to install them right?
take the idle mixture screws all the way down, don't force them, and back out 1 1/2 turns.

You might also have no pilot circuit flow. Did you have to increase the idle a lot to keep it running? Backfires? It might be only running on main and mid circuit.

Start with remembering how you rebuilt them and then adjusting. If still no good remove them and check everything, including the pilots to make sure they are the right size and not damaged. A PO might have changed them and didn't tell you, cleaning the carbs means you're not compensating for other problems with carb tweaks.

Report back with what you find
 
pulled carbs out and checked pilot and air jet, both definitely factory sizes and appear undamaged. pulled choke needle and it is covered in fuel. I am going to get some stiffer springs and see if that helps.
 
Check the needles for closure. If the are closed you shoul Not be able to get fuel past them. Spray carb cleaner from inside the bore and see if it makes it to the feed tube in the bowl
 
tmp_21438-IMAG0010-1170045031.jpg
Here are my pilot screws for reference. They look good, correct?
 
Before I took everything apart again. I ran it for a few seconds. Pilot screws at 1 1/2 turns out. Started with no choke and would bog down with choke on. And the carb passage and manifold boots were pretty covered in fuel. Should I lower the fuel level slightly?
 
Choke plunger appears to be sealing. And pilot plugs are brand new. All jets are definitely factory sized. Would the pipes require some jetting?
 
Zero260 said:
Before I took everything apart again. I ran it for a few seconds. Pilot screws at 1 1/2 turns out. Started with no choke and would bog down with choke on. And the carb passage and manifold boots were pretty covered in fuel. Should I lower the fuel level slightly?
Click to expand...

The bike should bog down when you pull the choke, if it is not required to run, that is why you had all the excess fuel on the boots and passage.

Double check your throttle cable routing and adjustment and lubrication to eliminate that as a possible cause. Have you synced your carbs yet? If not do so, then adjust the pilot circuit to lean best idle. When that is done you have eliminated almost everything but a vacuum leak.

V
 
The screws that are backed off about 2 turns are the idle/air mixture screws -these are on top of carbs close to carb boots. As mentioned, each carb has pilot jet under a rubber plug close to main jet. Are you sure you have the correct pilot jets?
 
yes. factory jets are 40 and so are mine. I read somewhere on here that their are 2 different types of pilot jets, with holes and without. I'm almost wondering if I have the wrong type :confused:
 
I noticed on my air box one of the carb boots is loose in the airbox. it has a mall amount of movement(or slop). it's easy to turn and can wiggle a little. The rest are tight and need a little force to turn. would that be enough to cause hanging idling?
 
duaneage said:
You might also have no pilot circuit flow. Did you have to increase the idle a lot to keep it running? Backfires? It might be only running on main and mid circuit.

Start with remembering how you rebuilt them and then adjusting. If still no good remove them and check everything, including the pilots to make sure they are the right size and not damaged. A PO might have changed them and didn't tell you, cleaning the carbs means you're not compensating for other problems with carb tweaks.

Report back with what you find
Click to expand...

I do have to have the idle screw, the one that holds the butterflies open, in about 3-4 turns to keep it running. Other wise it will stall. Where should it be at?
 
double checked my fuel level and I had 3 carbs under 5mm so I raised to the float to lower the fuel level and it seems to idle better and responds better to pilot adjusting. but after a 10 min test run I am loosing power in my midrange(1/2 to 3/4) throttle. I haven't messed with the needles yet. Does this mean I need to raise them slightly like recommended in the carb rebuild tutorials?
 
The Bleed and Non-Bleed jets are supposed to be interchangeable. Factory ones are with holes on the sides, that is the Bleed type
 
Sounds like fuel is not getting through the pilots to the idle circuit. Wearing safety glasses spray carb cleaner through where the pilots install and see if it exits in the bore from the tiny holes beneath the idle mixture screw. I rebuilt a set of keihin carbs twice but still had blocked pilots. I put copper wire through and cleared the passage
 
duaneage said:
Sounds like fuel is not getting through the pilots to the idle circuit. Wearing safety glasses spray carb cleaner through where the pilots install and see if it exits in the bore from the tiny holes beneath the idle mixture screw. I rebuilt a set of keihin carbs twice but still had blocked pilots. I put copper wire through and cleared the passage
Click to expand...

That's what I thought but when i was checking the choke I sprayed through all the passages and it does come out by the pilot screws
 
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