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R1150RT funky idle issue, suggestions needed.


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My '02 RT has had an idle that a bit odd. I'll try to describe it; the bike starts fine, but whether cold or warm when it idles it revs at about 1000-1100 RPM, but then it drops to 950 RPM for a second or two, then goes back up to 1000-1100 RPM, after 10 20 seconds it will again drop to 950 RPM for a second or to and back up to 1000-1100 RPM. Occasionally it will drop to 950 RPM and stall.


The above is without the pink plug, it will run much worse with the pink plug, stalling quite often. The valves and TB synch are fine, and it runs well otherwise. My thinking is that the ECM is the culprit (maybe the fuel mixture is lean). Another thought was to purchase a Techlusion which may help.


Any thoughts or suggestions?


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Strange idle and poor drivability at low RPM may be due to vacuum leaks at or around the throttle bodies.


I have routinely removed both of mine, cleaned them thoroughly with carb spray. Remove the brass idle air needles out completely and clean them thoroughly.


Reinstall everything with a bit of grease(I prefer silicone O-ring lube) grease at the mating surfaces to insure that there are no air leaks. This has produced an extremely smooth idles on my ’01 GS. Also, TB syncs are almost a thing of the past (my Motion Pro manometer is gathering dust).


Also, take a plug reading. Is there any evidence of plug deposits?


Finally, Autolite plugs improve idle, reduce detonation and reduce combustion chamber temperature during summer heat. I run Autolite 3923s in winter, 3922s (one range cooler) in summer here in Texas.


Do not go the chip route……you’re merely covering up something that needs a bit of tweaking. The chip will likely add more fuel and may not provide any remedy at idle..not worth the expense, in my opinion.


Also, make sure the pink CAT plug is the correct one for your application.


The BMW Motronic works just fine when the rest of the engine is properly adjusted.

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I would check the TPS voltage. While there is no "zero-zero" adjustment procedure on the 1150, if the TPS voltage is right at the ragged edge of .400, it may cause the hunting you describe. Then do the throttle range reset procedure.

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Thank you, all good suggestions!


I've already replaced the TB o-rings (lubed) at the time I installed the GS intake tubes. (Problem existed before the GS tubes.) But I didn't take out the brass screws for cleaning, will try that next.


Am aleardy using Autolite 3923s. The original looked fine though when I took them out.


Suggestion that I should put back the pink plug (correct one), but how do I confirm that the one I have is correct (p/n, batch, s/n??).


TPS voltage, at the edge of 0.4V?? What should it be, and is it adjustable (tuneable)?



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Check the resistance on your plug wires and coil. Replacing mine resolved a similar problem. I agree with the rest of the suggestions as well. Added autolites at the same time.

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