I have a 2004 R1150RT and the fast idle lever on the left side handle bar control area seems to have no influence on the idle rpm. Is this a adjustment issue or something else entirely?

Adjustment or broken/unhooked cable. With the lever all the way on try pulling on the outer cable. If it accelerates then, it is adjustment. If it feels really loose, it is a cable problem.

Chuck, that happens a lot if the TBI balance involved changing one or both throttle cable lengths as that also effects the choke cable operational length..

There is s rubber boot covering the choke cable up by the left handlebar,, slide that boot down the cable a ways & you will see the choke cable adjuster.. The proper (re BMW) adjustment is “0” play but I never set mine that high.. Maybe try 2100-2200 fast idle speed on a hot engine then adjust from there if not high enough cold..


Twisty

A small amount of extra slack in the throttle cables after a throttle body synch will stop the fast idle mechanism operating altogether.

The fast idle cable (2) pulls on a shallow ramp in the cable junction box to move the throttle cable pulley very slightly. The movement is so small that any excess slack in the throttle cables (4) will use up the movement entirely without actually opening the throttles at all.