Two engine numbers

Hello all,
I been looking around the Norton boards for a while trying to get as much info as I can (I think I'm near to overload !). I have just got a 71 roadster which was imported back to the U.K. around 18 years ago and its been standing in my neighbors garage. The engine has stamped BMS and a number matching the frame number 143xxx but also another number 209xxx, Oh and the engine has broken the left hand con rod and is missing barrel and head etc. so there is loads to do!!.
Thanks in advance
John

Hello John,

And welcome to the forum.

I'm not quite sure if you are asking for information about those numbers, or whether you are just giving us some details about your new acquisition?

I don't know what the "BMS" stamp is? Is it stamped next to the engine number? The 143xxx number would be from early 1971 production.
Could you say where the other 209xxx number is stamped, as that number would be from 1972 production (if it is stamped on the gearbox top lug, then the gearbox or at least the gearbox casing has been changed? If it is also stamped on the engine casing below the L/H side of the barrel, then it could be the original number? So the engine could be from a 1972 model that has had the old engine number added to it?

I know of no original set of cases with double / different stampings.

Welcome John!

Does the engine have the crankcase breather from the end of the cam or at the back of the crankcase?

The mark BMS and the engine numbers are stamped one above the other in the space provided on the left hand side of the crank case. the breather is at the back of the crankcase and it has the smaller drain plug. The only number I could find on the gearbox is NAxxxx so I'm not sure if that's original. The frame has a rough hole in the top together with a slightly bent down tube and has been crushed by a third party side stand. So I think its going to be a long restoration.

John Wright said:

The mark BMS and the engine numbers are stamped one above the other in the space provided on the left hand side of the crank case. the breather is at the back of the crankcase and it has the smaller drain plug.

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That would indicate it is a 1972 engine (or crankcases?) and the 209xxx number is probably the original one, if by saying "in the space provided" you mean a raised pad, that would also point to it being a 1972 engine or cases.

John Wright said:

The only number I could find on the gearbox is NAxxxx so I'm not sure if that's original.

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"NA" is from a pre-Commando box, and probably came from a Dominator twin or a single cylinder ES2 or Model 50?

BMS ? "Both Mains Shot" ? Just a thought ! Some rebuilders stamp their work, although this one doesn't sound like work to be proud of.

A couple of photographs would be helpful for a definite ID of specification.

To be honest, based on the damage mentioned to both engine and frame, I would see this more as a donor bike to restore another than as a basis for a restoration.

It's a very long time since Commando major assemblies were anything other than expensive. The combination of a popular model often used for competition with the ability to self destruct at quite low mileages means that things like decent second-hand cases and heads are not at all easy to find.

So its looking like a 1971 frame with a 1972 engine, the frame is rough and the engine is shot to pieces and I haven't looked inside the gearbox yet, Blimey I've bought another bargain.
When I find out how I will post some pics

79x100 said:

BMS ? "Both Mains Shot" ?

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hahahha i love it thats a good one! :lol:

John Wright said:

When I find out how I will post some pics

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Here's how: http://accessnorton.com/norton_commando2357.html