The rear sub-frame is bolted at the top however there is also a long steel bush on which the sub-frame pivots which needs to be driven out of the frame. Heat the area first as the bush will be rusted in position.
Take out the two bolts in the swinging that attach the bottom of the rear sub-frame this will reveal the swinging are pivot pin – if you are luck it will just drive out with a hammer and suitable drift. If it is rusted in the frame then apply heat before attacking with a hammer.
While not the best – try buying a copy of the Haynes Manual for BSA singles – it will give you the basics.
