engine identification numbers

Mar 17, 2007
Hi everybody,
I am new here as I just got my first commando, 1972 roadster.
I have one question:
the engine is not stamped with any identification numbers ??? the old chap who sold the bike to me swer that the engine is the original one and he's telling me that once he even read in a norton book that some 1972s commando where not stamped on the engine ??
is this possible ? any suggestion ?
It appears to me that he is telling porky pies!

The engines were stamped with a number on the left hand side on the crankcase below the barrels. It is an oblong flat section with the number stamped into it,

I have a 1972 Commando with matching frame & engine numbers - Have a look at my website at picture 31 it shows where the engine number should be.
Hi Pete,
thanks for your reply.
on my bike there are no numbers where they suppose to be...........on the left hand side on the crankcase.....
the oblong flat section has not number stamped into it.....just plain metal.
I did look at your web site, nice bike.
cheers, Enrico
With the engine number missing it could have been ground off as the engine was stolen. If it was a different engine it should have numbers stamped on it and the new engine number listed in the log bog for the bike.

It all sounds a bit dodgey to me!!

I had a 1971 Roadster stolen in Oxford in 1976 two days after I had complete a nut and bolt rebuild to concours condition. I stamped the insides of the crancases, cluth, gearbox etc, so I could identify it. I found a bike with some of my parts on it and informed the police, only to have them acuse me of stealing the other bits? I was absolutly furious and showed them all of the reciept for the works done.

Did I get an apology? No

Never seen that bike since.
thanks Pete,
I am a bit lost here now.....
it does't looks like the numbers have been been grounded off, the crankcase really looks like factory make, just a blank oblong flat section.
the old man who sold it to me look honest, he's a pensioner and the bike was advertised in the oldbikemart in february and he had it for a long time.
also, the log book has not the engine number on it.......
Engines with no numbers were factory spare crankcases for warrenty repairs. Considering the numbers of rods that must have destroyed crankcases in 72 it amazing that so few turn up. Does not explain how the log book has no engine number but the DVLA don't seem to worry about engine changes just frame number changes.
Enrico, what type of crankcases are your unstamped ones ? Do they have the steel blanking plate on the rear of the timing chest or is it one casting ?

I have a January 1972 (but not registered until September) 750 MkIV (pre-combat actually), frame number 200*** and it has been rebuilt at some time in the past with new replacement 750 Mk V cases which are unstamped and still have the machining marks visible on the raised boss. My log-book still showed the original number.

I suspect that this was carried out quite early in it's life and as Kommando says, warranty replacement is the likely answer as within a few years, the breakers were full of ex-police Interpols being dismantled and an owner paying for it himself would probably choose second-hand components.

There are stories of Combats going back down the line for conversion to standard spec once Nortons realised what a problem they had and this caused all sorts of oddities in build dates but I have not heard of any without engine numbers. That said, there are some indications that quality control was not a strong point around this time :)

Just one other thought, does your gearbox have a number stamped on the top case lug ? It should match engine and frame. It won't prove anything but might give some idea of originality.

If you have got Mk V cases, don't worry, they are generally regarded as the strongest of the 750s.
I'm not an expert but I believe that the cranckases are the "one casting" type.........
I will check the gearbox as well for any numbers
I have a couple of pics of the engine, but how do I post them here ??
by the way....thanks everybody for your help
enrico said:
I have a couple of pics of the engine, but how do I post them here ??

You could open a free account with Photobucket http://photobucket.com/ (or another photo hosting website?) upload your photos, then either copy-paste the IMG address line below each photo into your message (to insert the photo in your message) or copy-paste the URL line into your message (that will insert a link to the photo). Or you can make your Photobucket album *public* and post the album link. Use the *Preview* button to check everything is OK before posting.

Replacement crankcases would not have generally have a number stamped on them (as others have said) so there may be an innocent reason why there are no numbers on your cases.
Enrico, the pictures are not quite close-up enough for me to be certain but they look like MkV (1973) unstamped cases. Once they became available, the earlier pattern seem to have been discontinued.

Your bike has some nice period mods (Lucas RITA) etc and is not 100% factory standard and looks like it has had a caring previous owner. I assume from the alloy clock holders and early rear light that it is a 1972 bike and the most logical explanation is that it cracked a drive side crankcase half early in its' life and gained a set of the latest pattern cases.

Mine is just the same (although it started out as a drum-braked bike with 30mm ports)

I really don't think that you have anything to worry about. I wouldn't be inclined to stamp the cases as you will never obtain the correct form and then it will look as if you're trying to hide something ! It looks like a cared-for bike with some previous history - cherish it ! :)