Airvelocity is the one thing which makes the mixture in the carburettor. Without any air passing by at a decent speed will result in a poor mixture. If you fit a bigger carburettor, the airspeed will drop, which means the pressure drop around the venturi, where your main jet is fitted, will also decrease. There is an optimum for every setup, but the way I see it, a 28 mm carburettor is too big. High airspeed alsos has the inertia effect, which means if the reed valve wants to shut because of the changing crankcase pressure (because of the rotating crank), it still wants to go forward because of the high speed. Try stopping your moped at once, while driving 40 km/h. No can do ;). Same goes for air speed.
Well, the more mixture you can get in the engine, the more power it will generate. If the airspeed is too low, the throttle response will be sluggish as hell, and the mixture quality also isn’t wat it is supposed to be.
You’re absolutely right about the part about engine torque. The engine doesn’t generate more torque all of the sudden when a variator is fitted. It just transfers the engine torque in a different way, which can be calculated quite easily.
@Millen, a jet = sproeier in Dutch.
grz Thijs