carb size - gas mileage

Wondering what sorts of mileage numbers people out there are getting with various kits and carbs. I'm putting on a 50cc kit, and I'm trying to figure out what size carb to use. Initially, I was thinking 16mm (PHBG, not SHA), but I know that something like 18 or 19mm will get me more top speed. Mostly I'm wondering what the difference in gas mileage is in this range (15mm-20mm) of carburetors.

Re: carb size - gas mileage

I had a 25mph Moby with 10mm intake and 10 mm carb which was supposed to get 143mpg stock. Oddly, I believe the 30mph version with 12mm carb and 14mm intake also was supposed to get 143mpg stock. Anyway, I noticed 120mpg.

After I put on a 70cc motor, with 15mm carb on a 14mm intake, I was getting about 90mpg. I am building a new bike with the same motor, but with a 15mm intake and a 13T front gear instead of an 11T, and I am expecting 100mpg.

Once I put on a 19mm intake with matching carb, I will see what mileage I am getting. I should also note that expansion exhausts should improve gas mileage, since they push unburnt mixture back into the combustion chamber.

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