Hi all , thanks for the replies, it is a twin disc, and the frame no, is 6351567. which when put in the BMW real oem parts, the bike comes up as a 12/1981 248nr65 ls Europe. production code 0359. The rocker covers have been painted black, and the exhaust is a geniuine Bmw one.
The front indicators are not original, probably due to no nose cone. I will be sealing the tank soon although not leaking with por 15 for peace of mind, and would like next year to respray the tank, mudguard and side panels and seat hump. I shall also probably purchase some more rear shocks for some 2 up touring next year and put fresh oil in the front forks. I intend to ride it pretty much as it is though. I replaced the sump gasket because the oil leak would not go away and i feared stripping a thread so that is all good now. I may strip down the l/h cylinder as it leaks a drip of dino oil in time, its not the seal but comes from the valve guide itself( i think) at least it runs down the valve sleeve from somewhere and ends up on the side stand, not a lot but i know its there! Other than that i commute 30 miles a day to work and use at weekends.