[Reg in Bristol]

Looks like it has a snap ring, my beemers like that

If so, you need to use a lever or grab it with

vice grips and tap it off

 

[Reg in Bristol]

Unless we get the voice of experience to give a definitive answer

I'd suggest pulling the boot way back and checking there really is no bolt

If so, I'd use gentle to moderate leverage to see if the UJ will move and

pull away from the output shaft.

maybe you need to pull the motor forward a bit too?

Obviously someone who's done the job on a 650C would be the best guide.