Which sub model is this 1973 Commando

Wow, correction . Closer inspection of tag on neck shows oct 72. Also found a C on the head under the engine steady.
 

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So looks like a 1972 Commando Combat. Research shows the issue with the main bearings. Unknown miles. Have to decide to either prep it for a start, been stored for years , or start a rebuild.
 
Daytonachuff said:
Wow, correction . Closer inspection of tag on neck shows oct 72. Also found a C on the head under the engine steady.
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OK, that's better. It's a 1972, not 73 probably not a real Combat. Service Release N3/23 appears to say that 211110 was the last Combat (or first after Combat) yours has too high a serial number. However, sometimes they did not pass inspection and were later finished so it's possible. AFAIK there's no way to be sure because the 72 dispatch records did not specify much more than the date and serial number. So, maybe the head was changed, maybe they used up an existing head, maybe it was finished later.

BTW, the follow on RH6 heads were basically the same but only skimmed .020" not .040" so after the Combat, there was the high-performance version but AFAIK, it was not marketed that way - not sure.

Does the certification label (red label) serial number match the engine and gearbox numbers?
 
The model year production normally started in Aug the previous year so the new model year bikes were on the showroom floors in Jan of the new model year for the new sales season. So you still have a 73 Model year bike, its just happens to have been made in 72 but to 73 model year specs. It would have likely been sold out of the dealers in 73 and Titled as a 73.
 
But we know Commandos didn't have model years in the normal sense so the model year is whatever it says on the documentation.

Blewdy Yaink

Post in thread 'What am I looking at?'

chaztuna said:
Yes, that is correct. The 4 way switch will bolt right on, if you want to have the additional position.

Blewdy Yaink's explanation of how your 1971 model is listed as 1972 is almost correct. During the great depression, here in the USA, many auto makers were on the verge of bankruptcy. Fall and winter were traditional periods of slow sales for new cars. The horrid economic climate made things much worse. The manufacturers asked the US Congress to pass a law to allow them to move the start of the new model year from January 1st to the previous September 1st. This would help...
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kommando said:
The model year production normally started in Aug the previous year so the new model year bikes were on the showroom floors in Jan of the new model year for the new sales season. So you still have a 73 Model year bike, its just happens to have been made in 72 but to 73 model year specs. It would have likely been sold out of the dealers in 73 and Titled as a 73.
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I disagree. It is widely understood that 220000 started "73" and since Norton did not have "model years" it's best not to say that. When they discontinued the Combat engines that did not mean that the non-Combat bikes were changed. When they started using RH5/RH6/RH6S heads, I don't know but that in itself did not make them "73". It was more about the instrument holders and taillight than head, IMHO.
 
L.A.B. said:
It's perhaps interesting to note that the post 212278 750s were apparently made to MkV specification but are not considered to be MkVs.
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Also a little weird (unless I missed it) that the "73" brochure only mentions the 850s but the "73" owner's manual (063852) has both the low and high compression 750s and the 850s. I guess they were having trouble figuring out the right marketing strategies. Of course, the brochures and owner's manuals do not specify the year so they could overlap as needed.
 
olympus said:
Can i ask, i know the main differences between a pre combat engine & the Combat .... but when it was discontinued, was this engine given a "name" and how did this differ internally from the combat??
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There were three heads: RH5, called low Compression but actually only slightly less than the original heads and RH6/RH6S which were called high compression but less than Combat. The Combat heads were skimmed .040" and the RH6/RH6s were skimmed .020". The RH6/RH6S bikes are called "High Performance" in some places but AFAIK, Norton said little to nothing about it.

Not sure about the cam - @L.A.B. probably knows - maybe that's where the 4S cam was used?

The "S" heads just meant 850 cast iron valve guides.
 
olympus said:
but when it was discontinued, was this engine given a "name" and how did this differ internally from the combat??
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A name? Not that I'm aware of. The later engine didn't have the Combat camshaft and eventually not the Combat cylinder head. Later engines had the standard camshaft.


marshg246 said:
There were three heads: RH5, called low Compression but actually only slightly less than the original heads and RH6/RH6S which were called high compression but less than Combat.
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Actually four as the RH1 30mm intake head is also listed in the 212278 parts book.
 
L.A.B. said:
Actually four as the RH1 30mm intake head is also listed in the 212278 parts book.
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Do you know if any bikes after 212278 were actually built using the RH1 head? I assume it was just there to provide info on replacements for bikes that used it.
 
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