Without knowing the outer diameter of your rear tyre it is difficult to say how high you gearing actually is, but I suspect that your 3:1 ratio is probably a bit too high. I roughly estimate the calculated top speed at maximum motor rpm to be around 120mph, and 10kW is not sufficient power to achieve that sort of speed with the amount of aerodynamic drag your bike will produce.
I would suggest that a 5:1 ratio would be a much better option
(55T rear sprocket) as it would give a maximum calculated speed of around 70mph with the added benefit of 66% more torque at the wheel.
Check out
this video for some useful information on gear ratios.
Alan
