Inliners International Forums General Discussion Engines Why isn't a 390cfm carb good for a 250 motor?

The Sprint is a 12 port motor with quite a bit of cam timing, fairly good iron exhaust, and over 10:1 compression.
I would guess that the primary jetting is too lean for the primary metering rod cruise step, the air valve tension is too low, and the secondary rod is too rich.
Easy to play with, just do one circuit at a time.