This is most widely used hubmotor for diy onewheeled electric skateboard
Technichal Data:
- Voltage: 60V
- Rated Power: 600W
- Size: 10inch
- Tyre width: 150mm
- Axel out length:31mm
- Shaft diameter: 14mm
- Poles: 30
Test Data in VESC Tool 
ERPM is 4519 , under 24.3v inputs with no loading , the calculated KV is 12.39

 
4000W motor spec:
Size:   Stator : 105*95mm 
Max voltage: 72V
Rated power: 4000W
Max current :  100-120A
Speed : 70km/h
Torque: 50Nm
Cables: 4mm²
Recommend to use this UBOX to work with it .
 Test data for 4000W motor in VESC tool
 ERPM is 12744 , under 41v inputs with no loading , the calculated KV is 20.72