sounds like your throttle slide cut away my have gotten out if size for the mods you have done
first verify your initial timing and timing advanceand i found some old notes (old)last race bike i messed with had thisPilot - 35Cutaway - 2.5Main Jet - 260Needle Jet - 159Q0Needle - 6DP17 in second groove from topno air correct jet
How large, "inside" diameter is the fuel line from the petcock to the Y? Cheers, 50gary