Sticky RPMs

[Codoloco]

So my throttle snaps back, as it should, when the bike is off. Everything seems fine until I fire it up, twist the throttle and it sticks, then slowly revs down again.  The twin butterflies seem ok and snap in place when off but when I fire it up, it sticks with the twist. 

92 slingshot, lunchbox, slip-on, 40 -147.5 and a recent carb kit rebuild... potential rebuild.  I know by changing and rejetting anything opens up a whole different story but it's tuned up fine, it just sticks.. right? ...right? Ugh

A new throttle cable maybe?
Carb cleaner?
A relook and think?
Idle air screw?
Fuel/air screw?
Ugh, bike shop?

[sledge]

I think you are describing a Hanging idle.

This is one of the most talked about issues in the history of this forum!!

It's usually down to an air leak between the carb and the cylinder but if the carbs are producing a lean mixture you will get similar symptoms.

Plenty and I mean plenty has been said in the past, I suggest you search and find something of relevance to your situation.

A good starting point: warm the engine up, take the revs up, let it idle back down,shut the engine off immediately, pull the plugs and take a look at them.

[mr72]

Most likely the idle is set too high.

Most likely you have set it too high to compensate for some other problem like clogged pilot passageway, wrong jetting, air/vacuum leaks, etc.

But hanging idle is technically, physically caused by the throttle plate stop being set too high so the throttle doesn't close all the way so you don't return to idle. This causes the slides to be held too high for too long which provides too much fuel and keeps the bike from returning to idle. After some time the vaccum levels are reduced and it will evetually drop the slides and return to idle.

[crackin]

Are the revs just hanging or is the throttle sticking? You say it snaps back when the engine is off and sticks when it's running. Does the throttle still snap back with the engine running and the revs hang or does the throttle stick? I'm confused.

[Codoloco]

I think you are describing a Hanging idle.

This is one of the most talked about issues in the history of this forum!!

It's usually down to an air leak between the carb and the cylinder but if the carbs are producing a lean mixture you will get similar symptoms.

Plenty and I mean plenty has been said in the past, I suggest you search and find something of relevance to your situation.

A good starting point: warm the engine up, take the revs up, let it idle back down,shut the engine off immediately, pull the plugs and take a look at them.

Thats great! that gives me something to look up "hanging idle"  didnt know how to search it.  Thanks!!  Ill  give it a good run and checks the plugs

[Codoloco]

Most likely the idle is set too high.

Most likely you have set it too high to compensate for some other problem like clogged pilot passageway, wrong jetting, air/vacuum leaks, etc.

But hanging idle is technically, physically caused by the throttle plate stop being set too high so the throttle doesn't close all the way so you don't return to idle. This causes the slides to be held too high for too long which provides too much fuel and keeps the bike from returning to idle. After some time the vaccum levels are reduced and it will eventually drop the slides and return to idle.

Ill have to go back and troubleshoot, maybe even through some seafoam through.  Good suggestions and interesting information as well 

[Codoloco]

Are the revs just hanging or is the throttle sticking? You say it snaps back when the engine is off and sticks when it's running. Does the throttle still snap back with the engine running and the revs hang or does the throttle stick? I'm confused.

Yes, the throttle still snaps back with the engine still running and the revs hang.  It doesn't hang for too long though, it almost seems like its delayed

[TheDooman92]

Any solutions?