Sprocket for a Electric Go Kart with a GM

[Demondres]

Hi, greetings from Chile.

First of all, sorry for my crude english.

I write because im thinking on buying a golden motor for a sand kart im building, but I need to know where I can find a compatible sprocket.

I know that a 1.5kw BLDC needs a 12mm diam sprocket with a key of 4mm.
Here is the picture:

http://www.goldenmotor.com/hubmotors/hubmotor-imgs/BLDC108-Drawing.pdf

I also like the 3kw BLDC but I don't have a clue on how to attach a sprocket to it. I don't understand the drawing.
Maybe 17mm diam sprocket with a key of 5mm?

http://www.goldenmotor.com/hubmotors/hubmotor-imgs/HPM3000B%20Drawing.pdf

I have seen pictures of the BLDC for tricycle series with sprockets, can I buy one of those sprockets?
Any info will help me alot. I am a EV newbie.

Thanks!