I just put an old SU carb on my 58 panhead. I had low RPM sluggishness that I could not completely fix by adjusting the nut on the fly. The next day, the bike backfired and sputtered for 2 miles before it stalled. I can't even kick it over now. Any ideas?

I hope by not being able to kick it over you just meant it wouldnt start but would still turn over. I run SU's on both my shovel and evo. Its very important that you remove the dome every so often and clean the inside of the dome and the slide. then lubricate with WD-40 and reassemble. Also just in case your not familiar with this carb you DO NOT fill the top with oil like they do on cars. If you have any other concerns Rivera engineering can answer them as they are the producers of the present day SU carb