1974 serial number question

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Jun 6, 2023
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My 1973 850 has a frame and engine serial number 303XXX
There is a 1974 for sale I might be interested with non matching numbers

The owner tells me that the numbers on the 1974 850 for sale are frame # 850F1066471, motor 20MS143830 (not matching he says)

I have not been long enough on the forum (only a year and a half) to understand how the numbers changed in 1974 and whether these
fit the year.

So if anyone can advise, I would be very grateful
Thanks
Dennis
 
My 1973 850 has a frame and engine serial number 303XXX
There is a 1974 for sale I might be interested with non matching numbers

The owner tells me that the numbers on the 1974 850 for sale are frame # 850F1066471, motor 20MS143830 (not matching he says)

I have not been long enough on the forum (only a year and a half) to understand how the numbers changed in 1974 and whether these
fit the year.

So if anyone can advise, I would be very grateful
Thanks
Dennis
850 frame, early 750 engine.

More info here: https://gregmarsh.com/MC/Norton/Info/CommandoID.aspx

It is not an 850 and even though the frame originally was from an 850.

The frame number you gave has one too many numbers after the F1 - should be 5, is 6.
 
The numbers did not change in 74 but for at least the Italian made frames an extra number was stamped on the headstock ie an 850FXXXXXX number which the factory did not record on the despatch records. However in the UK some dealers decided a frame stamped number was a better option than one stamped on a detachable alloy plate, so like my 74 its official registration paperwork lists the frame number as the 850FXXXXXX number and the Headstock plate with the Frame number matching the engine number is ignored.

For 75 MK3 it changed again and the frame stamped number was used by the Factory as the frame number.
 
The numbers did not change in 74 but for at least the Italian made frames an extra number was stamped on the headstock ie an 850FXXXXXX number which the factory did not record on the despatch records.
Not always true:

1974 serial number question


The dispatch records changed many times over time.

The early 850s had no frame numbers. All I've seen with the 850 F are 850 F1xxxxx and the xxxxx did not match the engine number. During May 1975 between the serial numbers 332351 and 332473, the frame number switched to 850 xxxxxx where xxxxxx matched the engine number.
 
My 1973 850 has a frame and engine serial number 303XXX
There is a 1974 for sale I might be interested with non matching numbers

The owner tells me that the numbers on the 1974 850 for sale are frame # 850F1066471, motor 20MS143830 (not matching he says)

I have not been long enough on the forum (only a year and a half) to understand how the numbers changed in 1974 and whether these
fit the year.

So if anyone can advise, I would be very grateful
Thanks
Dennis

Does it not have a tag on the steering head with a number perhaps around the 311### plus range.
The F number is probably from around January/February 1974.

That 20M3S 750cc engine (143830) is from March 1971. (or early April at the latest)
It is not an 850 engine so a purchase would be about the engine, not the frame. (If you were looking for a 20M3S 750cc powered bike, 1971 being the last year that engine was made/used)
 
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