High idle when warm

[jeffgs]

I just bought a very nice 1981 GS450T. The bike has low miles but is clean. It has developed a condition where as the bike warms up and has been running I would say 10 minutes, the idle RPM will start to climb higher and higher.

Other notes, hit the gas and it will drop back down.
It will start to stutter and stammer while they climb
Exhaust is pretty cool, I expect hotter exhaust which leads me to believe it is very rich
Has nothing to do with the cable
Choke is full off

I will be checking for vacuum leaks and have the feels the carbs may have the floats stuck and it is dumping fuel. If you have another suggestion I will take it. Just looking for some direction. I have a tendency to miss the easier things searching for bigger things.

 

[UncleMike]

Usually indicates intake leak.

 

[jeffgs]

Thank you

I tend to over think things

 

[chuck hahn]

And you set the idle on a fully warmed up bike. The cylinders become more efficient as they come to temperature..thus setting it when the engine is too cold leads to a higher idle when its warmed up.

 

[Gorminrider]

have a look here too
http://members.dslextreme.com/users/bikecliff/images/highest_rpm_plug_chop.html
note the pdf file available at the top of the page.

If you get no response turning in the idle-mixture screws, that's a symptom of a separate problem...ie leaking manifolds,broken screw tips,missing or broken o-rings on needles,dirty passages etc.