72' or 73' Combat engine Commando?

I'm in the middle of a long overdue complete rebuild of my "1973" 750 Commando.

I'm the second owner, purchased the bike way back in 1980, knowing not much about Nortons as my friends had Triumph Bonnevilles. The bike has a Combat engine ("C" stamped high compression head, larger valves, black painted cylinders, etc.). It is a matching numbers bike, s/n 212xxx. No less an authority than Brian Slark assures me that Combat engines were only produced for the 1972 models, and that Combat engines ended after 211110.

Furthermore, I had the engine rebuilt back in 1990 by British Marketing in So. Cal. and they confirmed that the engine had been rebuilt before I bought it. It had Superblend main bearings (the standard Combat fix), but also had the "standard" cam instead of the Combat cam. This work would have been done in Maryland where I purchased the bike and I'm assuming it was purchased somewhere in the state.

Color me confused; Do I own a 1972 bike that somehow got registered as a 1973? The head badge says the date of manufacture is Oct. 1972. That seems like a late manufacture date for a 1972 model.

I'm not all that familiar with combat bikes since I don't have one,.. edited to say and I proved it by posting mistaken information. Thanks LAB...

o0norton0o said:

Is it a big drain plug (standard model) or the smaller drain plug which was on combat models....

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All '1972' and '1973' 750 models should have the small drain plug.

LPCityNorton said:

No less an authority than Brian Slark assures me that Combat engines were only produced for the 1972 models, and that Combat engines ended after 211110.

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This is correct.

LPCityNorton said:

Do I own a 1972 bike that somehow got registered as a 1973? That seems like a late manufacture date for a 1972 model.

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The model year will be what is stated on the title.

LPCityNorton said:

It is a matching numbers bike, s/n 212xxx.

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That depends whether it's before or after 212278 as far as parts are concerned (I'm guessing after).

LPCityNorton said:

I'm in the middle of a long overdue complete rebuild of my "1973" 750 Commando.

I'm the second owner, purchased the bike way back in 1980, knowing not much about Nortons as my friends had Triumph Bonnevilles. The bike has a Combat engine ("C" stamped high compression head, larger valves, black painted cylinders, etc.). It is a matching numbers bike, s/n 212xxx. No less an authority than Brian Slark assures me that Combat engines were only produced for the 1972 models, and that Combat engines ended after 211110.

Furthermore, I had the engine rebuilt back in 1990 by British Marketing in So. Cal. and they confirmed that the engine had been rebuilt before I bought it. It had Superblend main bearings (the standard Combat fix), but also had the "standard" cam instead of the Combat cam. This work would have been done in Maryland where I purchased the bike and I'm assuming it was purchased somewhere in the state.

Color me confused; Do I own a 1972 bike that somehow got registered as a 1973? The head badge says the date of manufacture is Oct. 1972. That seems like a late manufacture date for a 1972 model.

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First, Norton had not "model year"! So, Oct 72 could be "72" or "73".

US dealers stated the year when titling the bikes and since Norton had no actual model years, they often used the year they got them which could have very little to do with when they were built and from a sales standpoint, later is better.

It's a likely a modified "72" non-Combat since the serial number is higher than the Combat cutoff but lower than the "73" start. "72" 750 actually started being built in 1971 with "72" serial numbers. "73"s were built in 72 and 73.

See: https://gregmarsh.com/MC/Norton/Info/CommandoID.aspx and

GME - Norton Commando Survey

Ongoing Norton Commando Survey of Serial Numbers, Dates and Related Information

gregmarsh.com

LPCityNorton said:

The bike has a Combat engine ("C" stamped high compression head, larger valves,

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The Combat head didn't normally have larger valves.

A lot of bikes were titled when they were sold, regardless of the tag. My 74 MKIIA is titled 1975 even though it was built in 74.

My 1972 June manufacture 750 Combat is titled 1973 .

US Motorcycle titling even was weird when there was a clear model year. From the late 60s, Triumph's "VIN" included the month and year of manufacture and Triumph had specific month cutoff for a model year.

I have a 73 Trident titled as 74, a 74 Trident titled as 73, a 74 Trident titled as 75 and a 74 Trident titled as 74. In other words, 75% wrong!

To recap you have a 1972 manufacture Norton titled in USA as a 1973. I might get corrected on this but the "C" head (using up inventory?) continued into 1973 but the cam was discontunied. So you have a high compresion 750 engine but not a Combat. I have a similar Norton Manufactured in Oct waiting for redo.

Thanks to everyone for such good information. It is fun to try and figure out the history of this bike that I have owned for so long. When Doc Brown shows up with his time travel DeLorean, the first place I'm going is back to summer of 1980 and ask a whole bunch of questions to the guy I bought it from (I suspect he might want more than the $700 I paid him for it).

Here's what I know: When I purchased the bike, it had a huge 38mm Mikuni single carb on it, Dunstall "2 into 1 into 2" exhaust and mufflers, no centerstand (due to the exhaust routing), and no grab rail behind the seat. It was a Black roadster tank and side panels with the Gold "D" pinstripe on the tank.

What I learned when the engine was rebuilt in 1990: The engine had been rebuilt before I bought it. It has the "C" Combat head and the Black painted barrels. It had the updated Superblend bearings but had the standard Commando cam. Also, according to British Marketing who did the work, the pushrods were slightly longer than what was supposed to be fitted to the Combat engine. They removed the end caps and slightly milled the pushrods to maintain the correct rocker angle for the valves. They also blocked off the breather at the bottom rear of the engine case, properly modified the cases and relocated the breather to the inside top rear of the timing case as is seen on later models. The engine has always run well and strong.

I've made a lot of modifications over the years (Boyer ignition, single twin lead coil, 34 mm Amal single carb, etc.) and now I've got it down to the bare frame to replace the isolastics with CNW stainless units and clean everything up while I've got it apart.

So my bike IS a 1973 model but the serial numbers indicate that it probably didn't leave the factory with a Combat engine in it. Somehow it did end up with the Combat head and barrels before 1980 when I bought it. Maybe it has a long ago local racing history on the east coast back in the 70's.

Engines get built, barrells get painted.
Other items tend to stay.
MK IV aka 72/750 had the Black barrells along with the polished, shallow gauge holders and smaller taillight.
MK V aka 73/750 had the 850 style deeper, Black gauge holders, larger tailight like the 850. Also had a 'Steel' gas tank from the factory.

I'm guessing you have a 'Hot Rodded' Mk V.

You don't say whether it has a front disk brake or not. I would hazard a guess that your motorcycle just has a Combat head on a post Combat s/n '72 Commando. All Combat head engines needed the pushrods shortened. Norton never shortened them after milling the head .040 to raise CR to 10:1. Main bearings in any rebuilt Norton twin are probably going to be Superblends by now. Painting the barrels black can be done to any year. You can change the cam to 2S if you want your Commando to be Combat spec. Moving the crankcase breather to the rear timing case would not be my choice, but if the timing side case was drilled to add holes, you'd have to plug them to go back. Just add a Reed breather valve now.
A single carb engine with Dunstall 2-1-2 exhaust probably didn't perform all that well in upper RPM's with stock cam.

More good info, thanks to all who continue to contribute. My bike has the front disk (stock Norton, long since replaced with a Lockheed racing caliper) also has the large tail light "square style".

The breathing modifications were done at my request when the engine was rebuilt in 1990. The directions for doing so came from the Norton Owners Club (The British one, not the US club) Commando Service Notes booklet that was written by Tim Stevens and John Hudson and edited by Alan Osborn in 1980. It was a good modification at the time when reed valve breathers didn't exist. I am fine with the engine how it is and have no interest in further modifications to it as it has always run fine. I'm focusing my work on rebuilding the frame and running gear with top quality components and getting her back on the road.

I'm not an originality freak as I have always liked the look of a 70's era Cafe Racer. I'm looking forward to posting a few pictures of my bike soon when this rebuild is finished.

Richard Tool said:

My 1972 June manufacture 750 Combat is titled 1973

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Probably sold in 73 so 73 entered on the title, my earlyish Combat left the factory in late 72 for reasons unknown but with a later mod to the milling of the cases but no doubt related to the main bearing fiasco. It was finally registered for use on the road in 74.


see pics 4 5 6 and 7 from top of page

212xxx were built in that awkward post combat period before the 220xxx 750 MkV was produced. The ones of this number that I’ve come across were titled as ‘73. My combat in the avatar was at the other end with Dec 1971 build on the red ID plate.

MichaelB said:

Engines get built, barrells get painted.

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Yep, every Norton engine I build gets black cylinders unless I'm building for someone who wants to show the bike and they are supposed to be silver. In that case, I would want to paint the head too. It's a personal preference - I detest two colors side-by-side that are close but do not match.

The head was very lightly painted silver too.