I'd go smaller on the air corrector, down to about 170 or so, and if it
still looks lean, go to 140 mains, then tune from there. You must have
DCOE40's, since you can't get a 28 MM for a 45. To me a 28mm choke sounds
awfully small. These are essentially 500cc cylinders, and from my bike
experience I'd expect a 34 to 36mm choke to be optimal.
With most carburetors, smaller chokes mean more venturi effect and therefore
a richer engine with the same jet setup as a larger carb. Webers have air
compensation and therefore all bets are off, since the compensator circuit
is probably more effected by pressure changes in the venturi, and it feeds
bleed air into the mix before it enters the throat.
I assume you are trying to get more low end grunt, since that would
generally be the aim of reducing choke size. I would expect your ultimate
horsepower to be low because you can't flow enough air through the carb at
high RPM.
I finally found a pretty good Weber book--Don't remember the exact title but
it's something like Power Tuning your Weber/Dellorto carbs. The odd thing is
that they don't say a thing about reading plugs, all the tuning is kind of
seat of the pants. But I found the book very worthwhile.
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