Engine and Frame Number or Vehicle Title to Determine Year and Model

Hello all,
my recently acquired Norton 850 Commando is titled as a model year 1974, which I believe would make it a Mk. II model. However, the engine and frame number is 306273, which shows it as a 1973 Mk. I model in the Norvil engine number chart. The plate on the steering head of the frame show a production date of “7 73“.
Should I consider this bike to be a 1973 Mk. 1, based on the engine/frame number and the date on the frame plate, or, per the title, a 1974 model, which I guess would make it a Mk. II? I know that things can overlap between years, and while a number may be stamped in metal or printed on paper, it may not be written in stone.

I am mostly concerned about this for using the correct parts, whether it would be parts for a ‘73 Mk. 1 or a ‘74 Mk. II. For example, I have read that the heads are different between 1973 and 1974. Are most other parts interchangeable between 1973 and 1974?
Besides pulling the heads and measuring the valve size or what ever the change was between the ‘73 and ‘74 heads, are there other clues I could see to tell what the bike is? It may mostly be a moot point for this bike as it has been changed in some ways: the pipes were changed to Dunstalls, the engine cylinder is not original and is black and marked “II 2” on the left side of the base, and “ANII” on the right side of the base. Is there a way to determine if it has the ‘73 head or the ‘74 head, other than pulling the head?
Again, my main concern is for how to consider this bike with the manuals, specs, parts and parts numbers.
Any insight you can share is greatly appreciated.

I suspect your machine may have been sold in ‘74 and titled as such- but I would trust the engine numbers and frame plate as identifying it as a ‘73.

I own a BSA A65L that is titled as a ‘73- which is clearly wrong. It’s a “Y” model and (if the internet is to be believed) is a 1967 holdover that was updated and sold in 1970. But I’m not going to argue that with the DMV.

Kane said:

306273


Should I consider this bike to be a 1973 Mk. 1, based on the engine/frame number and the date on the frame plate, or, per the title, a 1974 model, which I guess would make it a Mk. II?

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For registration/title purposes consider it to be "1974".

However, it is an 850 Mk1 so use the 1973/Mk1 list for parts, etc.

L.A.B. said:

For registration/title purposes consider it to be "1974".

However, it is an 850 Mk1 so use the 1973/Mk1 list for parts, etc.

Andover Norton Spare Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Genuine Andover Norton Parts created from the original drawings.

andover-norton.co.uk

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Great. Thanks

Another thing to mention, as I have heard that they changed at one point: the left side battery cover is plastic with the interior tool bag sleeve compartment, and the right side oil tank cover is metal with the graphics still there. I suspect that this bike took a lowside on the left side at one point and the left side cover may have been replaced. This bike is like rolling gumbo!

Kane said:

I suspect that this bike took a lowside on the left side at one point and the left side cover may have been replaced.

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It's more likely the battery access panel fell off at some time and was lost as they tend to do that when the Dzus fastener wears or the rider doesn't secure it properly.

Kane said:

Hello all,
my recently acquired Norton 850 Commando is titled as a model year 1974, which I believe would make it a Mk. II model. However, the engine and frame number is 306273, which shows it as a 1973 Mk. I model in the Norvil engine number chart. The plate on the steering head of the frame show a production date of “7 73“.

Click to expand...

L.A.B has already explained but two more confusing points. Unlike others, Norton didn't have actual model years. There are general date ranges where things happened but nothing close to an actual model year. In general, in the US, it was up to the dealer to get the title and whatever year they chose to put on the title is what it got - often depending on when the bike arrived to them or when they sold it.

There is more info here: https://www.gregmarsh.com/MC/Norton/CommandoID.aspx

This is even true for Triumphs which have an actual build month and year as a part of their VIN. I have a 74 Trident titled as 73 (74 model year built in 73), a 73 Trident titled as 74 (73 model year delivered in 74), and a 74 Trident titled as 75 (74 model year sold in 75)!

marshg246 said:

L.A.B has already explained but two more confusing points. Unlike others, Norton didn't have actual model years. There are general date ranges where things happened but nothing close to an actual model year. In general, in the US, it was up to the dealer to get the title and whatever year they chose to put on the title is what it got - often depending on when the bike arrived to them or when they sold it.

There is more info here: https://www.gregmarsh.com/MC/Norton/CommandoID.aspx

This is even true for Triumphs which have an actual build month and year as a part of their VIN. I have a 74 Trident titled as 73 (74 model year built in 73), a 73 Trident titled as 74 (73 model year delivered in 74), and a 74 Trident titled as 75 (74 model year sold in 75)!

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Thank you for that good information and clarification for how Norton conducted these things. I think many manufacturers are a little quirky with numbers, and mixing up what ever parts were on hand and needed to be used up to build a bike. At least back in the good old days.
Thanks too for the link to your site. It looks like a great resource with lots of interesting content.

Parts may have been change over the years, here are the basic visual differences between the two.

Mk 1- Silver barrells, RH4 head, straight chain guard without the black kicker, perforated seat.
Mk 2- Black barrells, RH10 head, chain guard has Black kicker, Square pattern seat.

A few others, Mk 1 intake manifolds are 32 x 32 to match up to RH4 head.
Mk 2 intake manifolds are 32 x 30 to match up to RH10 head.
Somewhere along the line, second gear ratio was chnaged.

The head markings are above the right exhaust and can usually be seen when tank is removed.

Welcome aboard....

MichaelB said:

Somewhere along the line, second gear ratio was chnaged.

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The higher second gear ratio was introduced on the Mk1A (from serial 306591), therefore, 306273 is unlikely to have had that.

(Edit: Chainguard extension introduced from 307091 according to Norton Service Release N3/55.)

MichaelB said:

Parts may have been change over the years, here are the basic visual differences between the two.

Mk 1- Silver barrells, RH4 head, straight chain guard without the black kicker, perforated seat.
Mk 2- Black barrells, RH10 head, chain guard has Black kicker, Square pattern seat.

A few others, Mk 1 intake manifolds are 32 x 32 to match up to RH4 head.
Mk 2 intake manifolds are 32 x 30 to match up to RH10 head.
Somewhere along the line, second gear ratio was chnaged.

The head markings are above the right exhaust and can usually be seen when tank is removed.

Welcome aboard....

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Thank you for the info on the heads! I can see the stamped marking above the right side oval valve inspection cover. RH4. And the barrels are black, but I know that they were changed a few years back when the engine was rebuilt, so they are not original. The chain guard is Mk. 1 and the seat is square pattern Mk. II! And it’s all good! I assume it’s a Mk. 1 gearbox, but whatever version it is I like it a lot. 2nd gear is broad and useful, and all gears shift smooth and quiet up and down, with the exception of downshifting from 2nd to 1st, but I really thinks it’s me downshifting too soon for this bike compared to what I am used to, and I end up in a ratchety sounding false neutral and the engine dies! And then I need to get off the road to kickstart it, which is very exciting and is probably good for all the cagers to see so that people get a glimpse of what real motoring was and can still be like.

My 750 Roadster is 1972 Manufactured date but titled 73 as that was the year sold .

Congrats! Our Norton's share birth months 7-73. Mine must have been the beginning of the month (306028) and yours the end!

That’s cool, so Norton made at least 245 motorcycles in July 1973. I wonder what the total production numbers are. How many handmade motorcycle could the factory produce in a month?
Are the numbers in series for all bikes overall, or model specific?

Someone will chime in on that question I'm not an historian on Nortons

Kane said:

I wonder what the total production numbers are. How many handmade motorcycle could the factory produce in a month?

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Total production is estimated to be 55,000 - 60,000 750 and 850 Commandos. The exact figure will probably never be known because there are gaps in the (mainly 850) dispatch records that were either lost or destroyed. Also gaps in the records where no entries are recorded so it isn't known if various serial numbers weren't used or if the details of the machines were not logged in the records.

https://andover-norton.co.uk/en/factory-records/

Kane said:

Are the numbers in series for all bikes overall, or model specific?

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Now, that's where it gets complicated.