Idle Fluctuating

[Rapid Dog]

'81 RS
Odd thing going on here.
Idle doesn't want to come down when coming to a stop or even just blipping the grip.
It comes down gradually. It's like 'over-run' for lack of a better word.
I've even seen it go back up to like 2K then back down while not even touching the grip.
Not stuck cables or even fuel I'm assuming as I've checked all that out, cables have slack, twistgrip not sticking or otherwise.
Carbs are synched. new slide needles which I've measured to make sure they are on the second notch.

Possibly the ignition module?
The ignition is all new Mororrad Elektrk Alpha.

[Boertjie]

Throttle return springs OK?

[Garnet]

Lay out your timming light and remove the timming plug. Go for a short ride, long enough for the idle to stay up, then pull into your driveway/garage and whip the timing light on it and see if the advance is hanging up.

The Motorrad Alpha has electronic advance, right? It should not stay advanced.

[Garnet]

A too lean mixture at idle will cause this sometimes.

[Rapid Dog]

Throttle springs are new, not hanging up, cables are new, carbs are rebuilt, all new jets.
This is something new that's happening.
The Alpha is electronic advance I do believe has a remote module under the tank.

[dwerbil]

Funny, my /7 behaved about the same a few years ago....the idle at a stop light would be high, then maybe drop down to normal after a minute or so. Duane's test nailed it for me --- when it's at the high idle, turn the ignition key off and back on in a instant...if the idle drops back to normal, the advance springs are worn and need replacing. The advance should be cleaned too. That fixed it for me. Dunno about your electronic ignition though. Good luck.

[George Ryals]

Plus 1 for too lean mixture.

[mattcfish]

Plus 1 for too lean mixture.

Yeah, this can happen if your butterflies are open to wide while adjusting mixture. You want them closed as much as possible (idle speed screw turned out) and still have the bike idleing with 1.5 turns out on the mixture screws.
Sticking float, enrichers not shutting off all the way? These are issues I've delt with that cause similar symptoms.

[05hexhead]

Have you checked for smooth operation of the throttle cable splitter under the tank? If there is to much slack in the top cable sometimes it can get hung up going into the adjuster.

[George Ryals]

Not fully warming the engine(20 minute ride) before adjusting the mixture screws is the easiest way to develop the described fast idle condition.