2002 K1200RS High Idle

[mehrten]

Our 2002 K12RS (ZG35448) began to idle high, 1,500+ rpms, several years back. My first thought was an air leak as the breather hose from the engine to the throttle bodies was cracked and leaking oil on to the engine and leaking extra air into the throttle bodies. I replaced it with no problems. Idle remained high.

Using a GS-911 I set the TPS and verified the throttle arm was working correctly. I tested the lines from the temperature sensor to the ICU and found no obstructions or loss in continuity. The fans come on about the time the water temperature hits just above halfway as they should.

Iron Horse Motorcycles in conjunction with Bee Mer Works found an o ring under one of the throttle bodies leaking. They replaced the leaking one, I replaced the other three. Slight change, then back to high idle.

Spraying a quick-start spray around the throttle bodies or the breather hose does not cause any change in the engine idle.

A known working ICU was swapped in and out. No change.

Used known good TPS and throttle arm pieces were swapped in and out. No change.

Early on I replaced the battery. No change.

I pulled the fuel pump out and found the screen was rotted away. The fuel filter was old. I replaced the entire assembly, fuel filter, pump, hoses, etc., with an EME pump. Cleaned the gas tank, fresh gas. No change.

I’ve pulled the wiring/relay cover off and fiddled with the massive collection of wires. I didn’t find anything loose or disconnected. No change.

I started the engine, let it idle until the fans came on. I shut down the engine and unplugged the ABS module. I restarted the engine; let it idle for a bit…still high.

I started the engine and let it idle until the fans came on. Then I shut down the engine and pulled out fuse 1. Started the engine…no change…high idle. I did that with each fuse. No change.

No matter what I’ve done, when the engine starts the throttle arm actuator pushes the idle up to about 1,500 rpms.

At that RPM across the battery terminals, it shows 14.2 volts. Iron Horse tested the regulator and found it functioning properly.

Note: Each time I disconnected the battery, I did the three throttle twists before restarting.

Next step? Starter relay problem? Problem with handlebar switch(s)? Bad plug connection?

Suggestions?

Deryle Mehrten
Sierra Vista, Az USA

 

[GTRider]

My guess: Your ICU thinks the bike is still cold or lean so it’s engaging the high idle setting. Since you’ve swapped the ICU without affecting the issue, I don’t think the problem is in the ICU. And, your checks on the mechanical linkages/settings and air/fuel plumbing pretty much rule out issues there.

That leaves the engine temp sensor—not the one that controls the temp gauge, but the one that speaks directly to the ICU. Either a bad sensor, or a bad connection, but the fact the ICU is engaging the fans after the bike warms is a contraindication—so I wouldn’t immediately fire the parts cannon without first checking the wiring to that sensor, and taking some cold/hot readings on its output. Normal failure mode on that sensor is for the bike to start running richer and richer to the point where it floods out and dies when the bike reaches normal operating temp- but will restart happily once cooled down.

Anyway, I’d poke around at that sensor and see what it tells you. #15 in this diagram, and come to think of it—I think this is the only temp sensor used on the later brick-k bikes.

Best,
DeVern

EDIT: And as long as you’re checking sensors, it wouldn’t hurt to check the O2 sensor as well.

 

[mehrten]

Devern,

As you said, strange that the brain seems to be getting a "I'm not warm yet signal" though the fans still turn on.

I'll play around with the temp sensor again.

Thought...

When the starter button is pressed isn't there an enrichment process that assists starting? Just because I can I'll pull the right handlebar apart and clean everything.

Does the starter relay have anything to do with the enrichment process?

I'll get back to the list in a couple of days.

Appreciate the help.

Deryle Mehrten
Sierra Vista, AZ USA

 

[PGlaves]

Remember that it is the amount of air that controls engine speed, not the amount of fuel. Too much or too little fuel will make the engine combustion too rich or too lean but would not generally cause increased RPM.

Added: If a mixture is too rich or too lean idle speed may drop and restoring proper mixture might return idle speed to normal, but mixture ought not cause an abnormal high idle speed.

 

[GTRider]

“Used known good TPS and throttle arm pieces were swapped in and out. No change.”

Does that mean both the throttle actuator and throttle valve switch (TPS) were swapped out with known good units? If so, was the TPS setting checked with the test unit?

Best,
DeVern