gregg ,
on my 400/4 , i used a stromberg , bit like an su but with a rubber diaphragm around the piston . it worked ,but the piston rise from tickover to 4000 rpm was about 5mm ,so not much metering adjutment on the needle profile available .
i then went to a yamaha xs650 twin cv carb , maybe a 32mm can't rmember , this worked well ,but max flow through it with the stock petrol tap ,was about 60 bhp .then lean . fitting a high speed enrichment ,gave me 85 bhp at 8500 then clutch gave up .i think for prolonged use at that sort of power and above i would need a much bigger tank tap .but the carb was good ,and gave me 45 to 50 mpg.
regards
robert