One thing I did see was that there is an oring around the main jet that can/does perish and fuel can then get past making the mixture rich, maybe that could be part of your sooty plugs scenario if you haven't been there yet?
Yes, new O ring in place.
Right, gotcha, see how the accelerator jet sizes out, hopefully you find something, I did read it is a stream and not a spray, could it be the float chamber was flooding? I have no idea, genuine question.
Gotta say Merv that you're past my direct experience with a Bendix too, which was just helping a mate install and then fine tune an adjustable main jet into a 1974 Sporty in 1980. So like Hilly I am following along hoping to learn something. But I do have 20 years of experience with Amals, Monoblocks, Concentric, and Mk 1.5 Concentrics (and one of them arrived new from the factory without the pilot air passage drilled completely through); 8 years experience with Mikuni VM28s off 1960s Kawa W2 650s, and the 35 years living with the CV on my 1200 Sporty.
Close to kicking it in the guts are we?
Maybe today Merv 😁
Well bugga Merv! I really hope the Mik sorts it, I just don't have enough real experience with the Bendix to offer anything other than encouragement, carburetors do get blamed for electrical issues though but you seemed to have that covered as well, I look forward to hearing how the next chapter unfolds.
Right, well going by generalised carby operation those ports are your transition ports from idle to main so yeah if those aren't supplying enough fuel when the air rushes past as the butterfly starts to open and before the main kicks in then the engine is going to bog lean, you should be able to actually see fuel coming out of them as you crack the throttle you would think?