You can replace your old 250 watt euro motor with the 750 motor as in the video. You will need a freewheel removal tool. I have done this swap, it?s a very straight forward job but you will need that removal tool. You can get a new motor from Gareth at Big Game Bikes in the U.K.   I?m not sure if your original controller will work the 750 motor as I changed mine to the 35 amp upgrade controller.  But Gareth will know if you ask him. 

I bought a bike from Rad nearly four years ago. I live in the U.K.  I wouldn?t buy one from them now though.

I have had zero replies from Bafang, just like Rad they are a shambles.

I recently got a new harness from Rad U.K. for my 2019 Radmini 4.   ?46.          Probably not very helpfull to you though. 

Similar problems here on Radmini 4. Solved by fitting new wiring harness from controller to handlebars.

Just checked the dimensions of my motor and they are the same as the G063. 1000 WATT H550 rear you posted. If you look up the G063 motor on Bafang website,  you can click on (Dealer Manual) at the bottom which links you to the G062 motor instructions.

Anyone found a diagram showing blue, yellow, green  wires in the KT controller functions?

JTK77, regarding the diagram of the Z916 to L1019  connectors, thank you, Do you know what each coloured wire does ?  We now know what these do from the L1121 that on the G063 motor MackWon posted .

Yep, that is packed. Easy to see that motors cam get a bit warm packed in like that. 

Note there is very little grease on the gears.

Inside the motor pic.

No problem so far with my mini4 charger in 3 1/2 years.

Thanks for the pin out info, that may become useful. Especially if a diagram showing what the original Rad push fit Z916 connector pin outs are.
I was also looking at the Bafang controller CR S307.1000.FC with the red plug connector to fit the G063 you linked to but wondered about connecting the other wires to the Rad wiring. It will probably require its own display as well. Bafang have been no help replying to me at all.
Maybe try to find a wiring diagram of the 35 amp controller to see if the coloured wire functions match the pin outs you show.

I have just swapped the wheel with the 750 motor back in and it still works with the 35 and controller . This would also rule out a throttle problem.  I also had the opportunity to hook up to an identical G063 1000 watt bought at the same time, this behaved exactly the same. Throttles up slowly then cuts out.   Looks like controller not communicating with motor. All 9 wires are the same colour but maybe don?t have the same function.   

Yes same controller