engine number

Hi I have a 750 Commando engine number stamped 204138 does any one know what year that is as the paper work I have says 20M31 30482 confused
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Gazza said:

Hi I have a 750 Commando engine number stamped 204138 does any one know what year that is as the paper work I have says 20M31 30482 confused
New member

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Engine sounds like a 1972? Do you have a frame?

no frame number not a classic, old school chopper been in a box for 30 tears all Norton though and all there

Gazza said:

... 20M31 30482

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130something means 1969 and no "S" after the 20M3 means your papers belong to a very early Atlas-style Commando. Nothing to do with the 1972 engine.


Tim

Thanks for the information much appreciated
That was around my reckoning from some of the info I have dug up
Just finished pulling the motor apart looks in good shape , gaskets and seals are the go and a clean up, check some tolerances .new thrust washers etc
Cam looks good is there anything I should be looking for ? Gear box next ??
Thanks
Gazza

Gazza said:

Hi I have a 750 Commando engine number stamped 204138 does any one know what year that is as the paper work I have says 20M31 30482 confused
New member

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The engine is definitely a '72

The serial number 20M3130482 is a very early 1969, when the Commando was only sold in one style (later called the Fastback). 20M3 was the model designation, to distinguish the bike from other models (Atlas, P11, N15, Mercury)

The engine for this early bike would have a tach drive screwed to the timing cover, driven off the end of the cam, and a distributor behind the cylinder, driven by a chain in the timing cover.

less than a thousand units after this number, the distributor was moved to the end of the cam, and the tach driven off the cam at a different point. These 1969-71 bikes were designated 20M3S.

With the '72s, Norton dropped the model designation, as they were only building Commandos, and had been dong so for a couple years

BillT said:

The serial number 20M3130482 is a very early 1969, when the Commando was only sold in one style (later called the Fastback).

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Not only Fastback there was in 1969.
There was the R type too (compatible with 130482).
Ciao
Piero

pierodn said:

BillT said:

The serial number 20M3130482 is a very early 1969, when the Commando was only sold in one style (later called the Fastback).

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Noy only Fastback there was in 1969.
There was the R type too (compatible with 130482).
Ciao
Piero

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You're right, it could possibly be an 'R'. Some of them were built with the distributor behind the cylinder, so before serial 131257, which I believe was the first 20M3S/ bike