Carburettor Angle question...

My motorised bicycle has a 70cc engine with everything stock, NT carb and 44T sprocket. I'm reaching a top speed of 40kph on a good, warm day.

I've read product reviews of the kit doing over 50kph.

I'm currently running approx 15:1 to 20:1 fuel (for break-in, but my next can of fuel will be 40:1), and my bicycle has been ridden for about 30 min everyday for about a month.

I get really good low-end torque, and I am blown away by its hill-climbing ability, but I want a faster top speed, specifically, around 50kph.

The carburettor is actually mounted at an angle, so if you look with your eye on the rear tyre, the carb is tilted around 20° to the right. I heard that these carbs work best when perfectly level because of the way they induce fuel through airflow, could this be affecting my top speed?

Ok, thanks. The carb was mounted that way because of a smaller frame size

Sorry for the newb question: what is a short billet intake? I've been thinking of getting some sort of intake mod, but haven't been sure which.

I live at close to sea level, weigh about 150lb/68kg, and I'm tackling some hills that are impossible to climb on a mountain bike except on lowest gear, on grass.

I've tried to cut down on rolling resistance by pumping my tyres up to almost 60psi (they're rated for 50), and I'd rather not spend money on tyres that wear even faster (these ones are only a month old and already almost worn).

Do you know what kind of RPMs my engine might be getting with 40kph on a 44T?