It's quite easy when you know how.
Grip the bottom end of the shock in a vice, and raise the lower chrome cover by hand. Underneath that you will see a hexagonal nut (15mm spanner size if I remember correctly). Loosen the nut and unscrew the bottom eye. You can then lift off the covers and spring.
the same technique applies to all of the 50/90 and 100 bridgestones and most other sub 125cc Japanese machines of the period.
I hope that solves your problem!
Graham Weeks
