High idle when hot!

[Wags87]

The 87 idles at about 1000 after warm up, but the more I drive it the higher the idle gets! Once it gets to nice operating temp the idle goes up to about 2500 and even gets to 3 grand. Any ideas?

[big mike]

The 87 idles at about 1000 after warm up, but the more I drive it the higher the idle gets! Once it gets to nice operating temp the idle goes up to about 2500 and even gets to 3 grand. Any ideas?

My 2nd gen repair manual says it could be due to incorrect carb sync, stuck choke valve, or idle adjust screw incorrectly set. My thoughts are start easy with checking your air filter and fuel filter. Hope this helps!!!

 

Big Mike

 

P.S. maybe its just telling you how much it wants to be ridden not setting at an idle!!!

[Neil86]

Two things come to mind....throttle cables/linkage drags from the heat of the engine, or a vacuum leak gets worse.

After warming up bike and getting the higher idle....remove side covers and observe if the linkage is resting against the throttle stop screw where the idle speed adjustment is made (between #1 & #2 carbs --riders left...knurled head screw that points down). If the linkage is resting against the end of the screw, the cables are returning fine...if not, lube the cables and check linkage to see they return to the stop screw with machine hot.

So if the cables/linkage are allowing the throttles to close against the stop screw, but its still revving....look closely at the hoses, and caps on the intake runners between carbs and heads....and the carb clamps for any vacuum leak draws in air...and works the same as opening the throttle butterflies.