Apropos of all this discussion about adjusting (turning) the cable that sets idle speed on the ST 1300 - before I did some serious disassembly on my ST 1300 (removing the complete throttle body assembly), it was impossible for me to rotate the idle adjustment cable. I thought - incorrectly, as it turned out - that the idle speed adjustment cable was a
Bowden Cable, the type of cable used on our bikes between the right handgrip (throttle) and the throttle bodies.
Once I got everything apart, I discovered that the idle speed cable is a single monolithic part - the entire thing rotates. I couldn't figure out why it was difficult to turn this cable when I had the throttle bodies off the bike and on the bench with the idle cable still attached to the throttle body frame - the cable rotated with very little friction.
But... when it came time to put everything back together, installing the heat mat, installing the throttle bodies, threading the idle speed adjustment cable underneath the left frame so the knob could fit in the little holder - that's when I discovered the cause of the "darn cable won't turn" problem: Coolant hoses, vacuum hoses, real Bowden cables from the throttle handgrip, etc. are all packed in there under the throttle body assembly so tightly that the idle cable was getting squeezed (binding) between these various parts. That's why the darn thing worked fine on the bench, but would not turn when installed on the bike.
The Honda Service Manual doesn't give super-clear directions about how to route this cable. I removed and re-installed the throttle bodies (with the idle cable attached) several times before I found a path for the idle cable that minimized (but didn't totally eliminate) friction on the cable from being up against other components. Finally, I applied a liberal coating of
Dupont Krytox lubricant to the outside of the idle speed cable where it fouled on other parts, and to the other parts that it fouled on. At last, I could easily adjust the idle speed cable when everything was put back together. I recommend Krytox because it is non-toxic to all the other parts around it (it is actually a food-grade lubricant) and it is stable at high temperatures.
So, some thoughts for other owners who might encounter problems rotating the idle speed cable:
1) It ain't the cable's fault. Like I wrote above, the cable is a single monolithic part, when you rotate it (either by the screw or by the knob), the entire cable rotates.
2) Although it is possible that there could be debris in the threads at the inboard end of the cable (where it screws into the throttle body frame) preventing it from rotating easily, it is far more likely that the cable is being pinched somewhere between the knob and the throttle body frame. You don't have to take the throttle bodies off to find the problem, it is sufficient to just remove the upper and lower parts of the airbox, this will let you see the path the cable takes and identify where it is binding.
3) Whatever you do, don't unscrew the cable from the throttle body frame unless you have the entire throttle body & cable assembly out on the bench. There's a spring over the end of the cable at the throttle bodies, it will come loose and fly away, and if you are lucky enough to find it, it is pure murder to try and re-install the idle speed cable onto the throttle body while the throttle body is installed on the engine.
4) Your first troubleshooting step, if the idle speed cable does not rotate easily, should be to remove the outside (right side) end of the cable from the little U-shaped bracket that it fits into, then push the cable inwards an inch or two. That just might free it up from whatever it is binding against. Once you get your idle speed set correctly, pull the cable back out and put the knob at the end of it back into the U-shaped bracket. If it still binds when in the bracket, great, be thankful - that will prevent it from turning and keep the idle speed setting where you put it.
Michael
