Sorry, i should have realied 'Starfire' is the later 'lightweight' type frame [bit after my bsa days] so here's another option [if not too late] At work we had numerous Yamy dt175's[& other similar] where the s/arm bolt would get seized in where it passes through the back of the motor, [as a lot of modern bikes do], couldn't get in there to cut ot off [not easily anyway] so lay bike on side & drilled in with larger & larger drills till it was gone prety much. Were usually seized in the steel sleeves running in the s/arm bushes as well--which has me thinking it must've been a hell of a long way to drill right through past the sleeves--maybe we managed to get motor out complete with arm after just clearing frame but don't think so. Anyway, food for thought. Cheers, ps looking at your pick with frame lugs bending, the old tube over & on the concrete floor trick then a good smack the other end [as described by me earlier] might still be the 'go'.