Is it not true that the smaller the carb the better gas mileage?

Example

My 2000 Grizz has a 40mm and my father inlaws Traxter XT has a 34mm. Same size of tanks and he gets great gas mileage, mine is a pig.

Is it because of the size of carb on mine!

Thanks

 

Yeah, that has lots to do with it. It's just like putting a 4 barrel on a car, compared with a 2 barrel.

 

A larger carb will pull more air (if allowed by the filter).
More air will require more fuel.
More fuel will be used.

A larger carb also tends to be more for top end, and less bottom end power, and vise-versa for the smaller carb.