R1100 idle issue

[Edgar]

I’m having idling issues with a ’97 R1100RT, 44k. The bike has had the valves adjusted, new plugs, throttle bodies are synced and in general the bike is running great. I just cannot get the bike to idle at 1100 rpm’s unless I have the BBS completely closed. I can sync the idle adjustment so the vacuum is equal, which a half a turn out usually pushes the idle up to 1400 rpm’s, at 1.5 turns or slightly higher, the rpm goes to 1500 rpm’s where it stays (no adjustability). The throttle bodies are very clean and the butterfly closes completely, and I have never heard a rattle. There is slack in the throttle cables and they are mounted correctly on the bell crank. The BBS and their openings are clean, and I don’t have a fuel controller on the system.

I suspect that there is an air leak somewhere and am considering replacing O rings. I recently replaced the air tubes with a GS type, but this was going on before. They are nice.

 

If you have been here before and have solved this let me know what you have done.

 

[smiller]

Well if there is an air leak causing high idle it has to be either at the manifold or throttle plate so the air tube o-rings wouldn't really come into play. If you can't find an air leak you might check your TPS voltage, if that is high it will cause high idle.

[T__]

Edgar, start with looking for vacuum leaks (on the engine side of the throttle plates).. If OK there suspect leaking or worm throttle shafts or TBI throttle shaft bores..

 

Other causes could be very advanced base ignition timing,, possibly too high of fuel pressure or plugged fuel return line,, leaking intake valve guides,, someone has messed with the TBI base idle screws..

 

What happens if you reach in with your hands & try to forcefully close both TBI units? If that slows it down suspect TBI shaft/bore wear or throttle plate wear..

 

Maybe play an UNLIT propane touch around the TBI shaft & “O” ring area & if the idle picks up even more that might point you to an intake leak..

 

How is your TBI balance when above idle speed? If OK there but slightly off at idle with closed BBS then maybe try slightly raising the low side vacuum with the throttle plate base idle screw (keep track of what you do so you can return it at a later time if you want).. If that requires the L/H side to be adjusted then be sure to also reset the TPS sensor..

 

 

Twisty

[Edgar]

10K miles ago, the idle was fine and adjustable. I haven't knowingly changed anything that might affect the TPS. Can it just change over time?

[smiller]

It doesn't usually change but it is an electrical part after all. Twisty's suggestions (also all good) don't normally change either but hey, something here isn't normal or your bike would be idling right. In any event the TPS setting is very easy to check and can cause this problem so worth a few minutes to verify. Google for a copy of the R1100 Tune-Up Manual which has the procedure.

[Mike T]

10K miles ago, the idle was fine and adjustable. I haven't knowingly changed anything that might affect the TPS. Can it just change over time?

 

If the TPS gets hit somehow it could cause it to move slightly which would change the TPS voltage setting and effect the idle.

[too old to care]

I had a similar problem on a 2001, R1100RT. Most of the time it would idle ok and the vacuum was even on both sides. However, sometimes it would idle fast. I did all the normal fixes and had no luck. The throttle bodies also looked like they were closing all the way, but as I discovered one of them wasn’t all the time.

 

I removed the throttle bodies and discovered that the throttle stop on the left throttle body was just a little lose in its mount. It is about .15 inches round in diameter and is held in place by being flattened out on the bottom much like a rivet. It would vibrate and sometimes stick in its mouthing hole enough to keep the left throttle body from closing.

 

The metal was too hard for me to smash it tight enough to hold secure, but a little JB Weld worked.