Here we go again.
These are both running 3hp 50cc cylinders with 25mm unrestricted exhaust headers and the intakes are 16mm ID.
I don't plan to do any porting but the carbs are only 14mm venturi's so there's easily enough room to go to 15 maybe even 16 without touching the top of the atomizer.
They are already jetted rich so I think I can get another 0.2/0.3hp just opening the carb.