I bought a brand new, not rebuilt carb in August, so there is no crud anywhere. Everything ran fine for 2 months or so, then it started running like crap. Started troubleshooting as per the manual, checked all stuff indicated, continuity, voltages, etc. The pins never moved, so suspected the stepper motor was bad. All measurements of resistance, voltage, etc, are as per the manual, both at MCU and stepper motor. Wiring checks out fine from MCU to stepper motor.
Bought a used MCU from eBay and plugged it in with no change in symptoms.
Returned the carburetor to seller, and just got another carb on Saturday. Plugged it in temporarily (stepper motor), and initialization doesn't happen, but the pins move in/out when the engine is cranked over, so at least it's alive now. I will try to finish installing it today and give it a try.
I heard about a posting on another forum, where someone has the same symptoms regarding no initialization but pins move in/out when cranking over, so I suspect the computer program was changed at some point in time, but the manuals weren't, or there was a tech bulletin published later.
Engine starts very quickly with the choke on. My problem is that it won't idle at all once choke comes off.
Carburetor was replaced because of erratic idle, etc, lots of play on the butterfly bushings. When the new carb was installed it ran great for a couple of months.
I can't do the nutter because of emission testing in Ontario, otherwise I would happily do it.