I really like the 33mm Pumper carbs from Mikuni -- Bore is slightly smaller than your current carb, but it'll throttle so much nicer with the accelerator pump.
I use it even with much bigger valves and cam and it'll still flow enough air to keep up. The same carb is offered in 42 and 45mm I think. The 45 is a monster and requires a billet head in my opinion. Realistically, your goal of 40 CHP isn't going to be attained until you go much bigger on valves and cam. Of course, everyone's dyno varies. On mine, a big valve ported stock head, .310 lift cam with 1.3:1 rockers and a 33mm carb is right at 32 CHP. Go slightly bigger on the cam and carb and you can realistically make 40 CHP. The billet head version with 45mm Mik. is right at 50 CHP.
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Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
interesting information . my combo started at 18hp stock and with 246 cam(stock rockers) on methanol and 36mm mikuni roundslide the computer says 31.3 hp so our numbers are close on your 32hp combo
out of curiousity, who makes this billet head and what cam are you running in the 50hp combo and what rpm range.
thanks.