High idle if warm

[ericjansen]

As a project for the coming year I have bought a '97 Monster. Not in the best possible state, but technically sound and for the rest just lots of time and efforts to make something nice out of it.

I just got one little problem which I want to settle before starting to take apart, and that is that the bike, once warm (>10km) starts to run on a much higher idle (~2000-2500 rpm) when coming to a stop. The rpm remains there, unless using the clutch and 1st gear to bring it down (after which it remains at normal idle, unless you turn the accelerator, then goes and stays high again).
If the engine is cold all runs fine though.

I checked the choke which seems to be fine, and goes all the way back, checked the throttle cables which are loose and moving smooth, the gas snaps back hard and seems to rest without obstruction on the idle adjuster.

Someone any idea of suggestion?