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Engine Numbers

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I have a Commando which I need to register with the DVLA for a V5 and age related plate. I contacted the club for information about the engine and frame number and it seems the engine number is documented as an 850, the barrels have the base nuts showing which I assumed made it a 750. The numbers are stamped into un molested casting not showing any signs of tampering. Can anyone shed any light on what may have happened, is it possible 750 barrels are fitted on the 850 crankcase?

 

Pip McQueen

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Your number is for a 1974 850. This should have an RH10 head. This would have 30mm intake ports.

Have you checked your head to see which RH number it has?

Have a look at the Technical section for the Commando under head identification.

Also have a look at this site. http://atlanticgreen.com/nhth.htm  

you will almost certainly get a lot of enthusiastic responses if you post this on the AccessNorton forum.

Be interested to know what you find out.

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I'm not convinced that engine number has not been re-stamped. The numbers are a bit uneven. There is a fair amount of metal on the cases where the number goes and have often thought you could file off old numbers & stamp new ones on. 

Or it could be a 750 top end on 850 cases. I think you can do that.

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Those are not factory stamps, by that time for an 850 there would be unique round stamps with horizontal lines before and after the numbers to stop tampering and they are missing. Those cases have been stamped later and 850 numbers have been applied to 750 cases.

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Definitely not a factory font style. Do the cases have a large sump plug ? If not then they're late 750...the large sump plug returned for the 850s.

It's difficult to say whether the casings are restamped or a new unstamped pair of cases have been used to replace damaged items.

Normally there are light milling marks visible on the raised pad.

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The engine number is incorrect, the breather is also in the wrong place, cases appear to be late 750. See attached for number and breather position.850 Commando engine number

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Thanks for all the input Gents, a bit of a blow to say the least but better knowing than not.

Assuming (and hoping) the engine numbers are not on the Police list where do I stand with dating of the machine and the DVLA? 

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Have a word with NOC Records. They're fairly used to this sort of thing and will be able to advise you.

There are some quite helpful notes on the links at the top of the page.

 

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If the engine number matches the number stamped on the red plate on the headstock then the number is not stolen, and if the cases were stolen then their real identify is lost. Most likely the frame number is the same, in the past the 850 cases exploded also taking the barrel and a 750 engine was substituted. 750 number machined off and the 850 numbers stamped on to keep the bike numbers matching. Just a likely guess.

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John,

as has already been well documented on this web site, engine and frame numbers on some Commandos are not always matching.

My 1974 850 MK2, purchased from new has non matching numbers. 

More Info here:-

Dyno Dave's Norton Commando Frame Serical Numbers - Atlantic Green Technical Services - British Motorcycles

 

Edit.

John,

Apologies you are correct about the red frame plate displaying the engine number because I've just checked my bike.

But I note that my V5 states the VIN as the frame sequence batch number which is the one prefixed with 'F'. 

Which is probably why I was confused.

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My MK2a is the same, red plate number matches the engine number, a separate frame number stamped directly onto the frame. The frame number stamped directly on to the frame was started about the same time the Italian frames appeared, not recorded in the factory despatch records until the MK3's so for some unknown internal use only until the MK3's. Did not stop the dealer using this frame number for my bikes V5 and not the number on the plate as per yours.  

In reply to by gordon_robertson

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The government can be assumed to not know norton historical numbering tradition post WW2.

For the commando the red cert plate is the "traditional" VIN/SN. The government later rules for longer # permanently stamped frame batch number, on the frame neck, some times are taken for the SN/vin. This seems to happen all around the world. They are the boss so you sometime have to do what they say.

Only in the final NVT days did the SN/vin become incorporated into a part of the frame batch number.

 

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