Is is normal for this to ramp up the idle to 4k when very cold ?
That is not my experience. On my motorcycle (2012 ST 1300), it idles at about 2,000 RPM for 2 or 3 minutes, then reverts to whatever idle speed I have set with the adjustment knob on the right side of the engine (1,000 RPM).
I am going to hazard a guess that the most likely cause of prolonged high idle, or excessively high idle, is not failure of the wax assembly but dirt or crud that is preventing the shaft in the wax assembly from freely moving up & down once the wax has melted, or dirt or crud that is preventing the throttle body mechanism from freely moving. The wax assembly, mounted on the throttle body assembly, is located in an area that is subject to accumulating all sorts of crap, dirt, dust, mouse nests, etc., but is extraordinarily hard to access for cleaning & lubrication.
Another significant consideration is that the shaft on the wax assembly causes the whole mechanism on both sides of the throttle body to move slightly (in exactly the same way that the throttle twist-grip causes the whole mechanism on both sides of the throttle body to move), hence, if there is any binding or resistance present
anywhere in the throttle body mechanism, it will result in slow operation - or no operation - of the throttle once the wax assembly warms up. So, I would not be too quick to point the finger at the wax assembly if initial idle is too high or if idle speed does not fall back to normal after a few minutes: the shaft in the wax assembly might be relaxing when it should, but the throttle body mechanism might not be free enough to move in response to the shaft relaxing.
Sounds like an emissions item that should be removed if it fails?
One would think that an electronically-controlled fuel-injected engine wouldn't need such a mechanical device.
Apropos of "emission control", although the initial high idle that the wax assembly creates likely provides emission control benefits (faster engine warm-up, faster catalytic converter warm-up), I doubt that is the primary purpose of the wax assembly. Keep in mind that the ST 1300 is a turn-of-the-century design (design was likely finalized in 2000 or 2001), and way back then, we were all using 386 computers that came without sound or video cards, and mobile phones that came in bags with shoulder straps. It's quite likely that Honda engineers thought that the wax assembly was the simplest and most efficient way to provide an automatic choke on the ST 1300 engine.
If I had a problem with prolonged high idle or excessively high idle, the first troubleshooting step I would take would be to remove the whole throttle body assembly from the motorcycle and thoroughly clean and lubricate it. Next, I would take great care when re-installing it (and re-connecting all the hoses & cables) to ensure that none of the moving parts of the throttle body or cables were pinched or fouled, and that the two small coolant hoses that connect to the wax assembly were not pinched or fouled. That's much easier said than done, as anyone who has done a re & re on a throttle body can attest.
Michael
