high Idle after engine is warm

[2K1SUPERVALK]

Hello all. I'm back. I bought Mr. Burnout's 2000 Interstate. When i start the bike it idles great. After i go for a ride and the engine is warm i come to a stop but the engine revs high. The only way i can get the rpms to come down is to leave in gear and ride the clutch. Can anyone tell me what to do? Damian

[f-Stop]

Hey Damian!


1st...check the vacuum hoses for leaks, cracks and bad connections...

But...it could be an air leak within the intake manifold system.  Check that the rubber tubes between the carburetors and the manifolds are seated properly and that the hose clamps are tight (there's twelve of those clamps).  Also, those tubes can become brittle and crack causing an air leak.  May need to be replaced.

Another thing that may have happened is that the o-rings between the intake manifolds and the cylinder heads have deteriorated causing an air leak there.

While you're in there, check the little vacuum hoses on the carburetor air cut valves.  As all vacuum hoses, those can become brittle and crack.

Good luck!

Lets go ridin'!

  Charlie

[Jess from VA]

My bikes (Interstates) have always had the idle go up after they are warmed up and ridden.

They also require some choke (enrichment) to reliably start (even in warm weather, but not for long).

I have tweaked the idle adjustment screw between the right side intakes down a little to bring the fully warmed up idle down, but that obviously makes the bike a bit harder to start cold (and more choke to start).  The manual says warm idle should be 900rpm, but 1k is OK.  The bike is not charging much at 900rpm or lower.

Sticking your fingers between the intakes to adjust the idle screw is best done before the bike gets hot enough to burn you.  Long needle-nose might do it.  

All the things posted by FStop are also relevant and bear looking at.  Snugging up all the intake screw clamps is easy to do.  

[da prez]

Basics . Also check the throttle cables. Be sure the adjustment is correct and the enrichment (choke) is fully released. It will hold the throttle at high idle.

                         da prez

[98valk]

your mixture screws need adjustment IMO.

    NOTE: A rich problem gets worse as the engine heats up.
        If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
    NOTE: A lean problem gets better as the engine heats up.
        If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

[Rocketman]

Let's start with a clarifying question:  How high is high? 

[JENTZ57]

I would also check your exhaust nuts at the manifold. This same thing happened to me and I had several nuts that had come loose over time and 2 that turned out to be stripped . Tightened them down and then it was fine after that.

Josh