Question about hanging idle

[glstine]

I finally got all the kinks out and my bike (1980 GS550L) is running better than it has since I've owned it. No more pops on decel, good throttle response, etc.

When I coast with the clutch pulled in the idle will hang around 1.5-2K rpms until I am almost at a complete stop. So my thinking is it is running lean. However, when I am at a stop, either in neutral or with the clutch in, if I blip the throttle it is instant up and instant down no hanging whatsoever.

Why does it hang when I am in motion but not when I am stopped?

 

[Larry D]

I finally got all the kinks out and my bike (1980 GS550L) is running better than it has since I've owned it. No more pops on decel, good throttle response, etc.

When I coast with the clutch pulled in the idle will hang around 1.5-2K rpms until I am almost at a complete stop. So my thinking is it is running lean. However, when I am at a stop, either in neutral or with the clutch in, if I blip the throttle it is instant up and instant down no hanging whatsoever.

Why does it hang when I am in motion but not when I am stopped?

First I'll say..the bike must be completely warmed up...say, after a nice half hour ride. That said....

Don't know why it would do it at one time and not the other...A hanging idle is normally either an air leak somewhere or the idle screws are a tad lean. Try turning the screws out to richen it up, but only about an eighth of a turn. If it still does it after you ride again, try another eighth turn. If you go to far, it will start to hesitate when you twist the throttle, it will really noticeable in 1st and 2nd gear.

You'll probably have to adjust the master idle knob at some point during this process...the big brass knob in the carbs.

 

[Dogma]

Perhaps just a blip of the throttle is not enough to trigger the symptoms?

Do you know that there are no leaks in the intake? What condition are the intake boots and o-rings in? If they are original, they need to be removed an inspected visually. Spraying things on the intake system looking for leaks can give false negative results.

 

[glstine]

Intake boots and O-rings are about 1 year old. I don't know about the airbox boots, though they seem to be in good shape. One thing I should add I guess, the higher the idle is set the worse the hanging is.

 

[Larry D]

Intake boots and O-rings are about 1 year old. I don't know about the airbox boots, though they seem to be in good shape. One thing I should add I guess, the higher the idle is set the worse the hanging is.

The higher the idle is set........how ?? If you mean by turning the master idle control, then....yeah, it would.

 

[gggGary]

carbs balanced with gauges?

 

[glstine]

carbs balanced with gauges?

Not since I took them off last to blast out the pilot circuit with carb cleaner and compressed air. (The carbs have been previously dipped I just felt that I had some sort of blockage somewhere in the idle circuit on one of the carbs). I've got a stock exhaust I am going to put on and was going to wait to balance them after that.

 

[glstine]

The higher the idle is set........how ?? If you mean by turning the master idle control, then....yeah, it would.

Yes with the master idle control, the difference between 900(+-) and 1100(+-) is significant (maybe this is obvious)

 

[gggGary]

My vote is balance the carbs. Unbalanced carbs have created the issue you describe for me, more than once.

 

[80GS1000]

Just to eliminate the possibility, is there any chance the throttle cables are hanging up or there's not enough slack in it to allow the carbs to return to idle?

 

[Larry D]

A carb sync can't hurt, if you have access to a manometer.

I think you're lean at idle, turn the screws out a touch and go for a nice ride. I used to carry a small screwdriver that would access the screws and tune as I rode. Not literally...I stopped first. It took about 3 or 4 rides until I got it right. I also had a small towel that I layed over the left side of the engine so I wouldn't burn my hand as I adjusted the master idle knob.