When Pat Orman (Calamus, IA) built vintage XL350 Honda engines into over 440cc hot rods, he insisted that owners use big 38mm Mikuni round slide carbs for raging maximum horsepower. Only problem with that idea is that the needle required (the 6CF1) was no longer available then. Pat had a small stash but it’s gone. I have a small supply of these needles which I offer to you for 25 bucks each.
I just learned from Nick Taylor in Owings Mills, MD that these needles are also the hot trick for TT500 Yamahas with 38mm round slide Mikunis. If you are building either bike for AHRMA, give me a call.
XL350 engine which Pat took out to 440cc-plus for AHMRA racing