Well, suspecting that the idle mixture was WAY off, due to who knows what, shoved a wire through it that blocked off about 2/3 of the flow. It's still really rich on the bottom end, but it was better. It didn't need so much throttle to idle now. I adjusted the throttle cable up 1/8" or 3/16" I was able to obtain a halfway decent sounding idle. It's still too rich, though, because turning the choke on makes almost no difference, and I know the choke curcuit really does shut off when I push the knob down.
As for the top end, I soldered up a main jet and drilled it out to 1/16". I even flow tested it against the 145 main jet that was too lean by installing each in the bottom of its own paper cup, filling them both, and seeing which one ran out faster. Not that I even believe that identical results in such a test would prove to be equal on the bike, but the 1/16" jet had a slightly higher flow rate than the 145 unmodified main jet, so it was close enough to go out and try. It ran pretty well this time. At WOT it still sounds flat below the powerband, but sounds pretty normal once inside the powerband. Can somebody tell me if this is normal?
So now it idles, has good transition most of the time, and performs fairly well on top. The biggest problem is probably that after descending a hill, throttle closed, it gurgles when you blip the throttle to clear a bump. This sounds like a rich pilot mixture to me. Perhaps the air jet passage or the airscrew passage still have a little junk in them. Or maybe the needle and needle jet are a bit worn. Something's causing a lot of fuel to flow at idle! Anyway, happily I have now burned about five gallons on a single spark plug:)