Thanks for response and stimulation to double double check. The number 14 appears on left side of of brass plate with norton patent numbers., indicating a 99. the engine number is the same, definitely C with 7600 underneath. The chassis number revealed 122 horizontally with 95988 vertically underneath. What I thought was 99 underneath vertical numbers is actually F5 upsidedown. The head is alloy. There are no markings on the barrels that I can find to indicate capacity.

It is a mix by the sound of it. The 122 means a 500 twin. If is is a latter 500 from the early 60s then it is a sought after bike. I agree with Rohan that photos would now help. Does the head have the carburetor mounting studs in the 12 oclock 6 oclock position or are they horizontal 3 oclock 9 oclock like a Commando? Latter heads have them horizontal. I wasnt sure about how early twin numbers come in. This is certainly a very early no and Rohan is probably right when he says it is too early for a twin. Is the frame a featherbed? You could search the web for a photo if you dont know what they look like. Can you see gearbox numbers? It could also have been reregistered and had new numbers stamped. I have a bike someone re registered in the UK with a slimline frame stamped with 1956 engine numbers. John

I managed to get further history of bike. It originated from Sumatra, probably brought over from Malaysia. It had a 500 twin engine with cast iron head that was swapped out for 600 twin engine about 12 years ago. The frame is a slimline so appears to be 61/62 frame with what we think is a 59 engine. Rides OK but seals in forks are gone and am in process of stripping down. We can maybe get new seals here. As I dont have any mauals as yet can anyone advise oil grade and capacity for roadholders. I have sent photos to rowan. cheers Paul.

Use about 15 or 20 grade fork oil. Amount is 150 cc but some people recomend going up to 175 cc. You might have fun with bits in Indonesia but if you can rely on the mail the NZ and UK suppliers can get you almostly everything. If it has a mag you might find problems and need to go to something more modern. Hot and wet - mags would love it !!!