1972 Commando 'Combat' Head Help

Hi All,

I've been getting deeper into the disassembly of my 1972 'Combat' Commando I recently acquired and have some questions. This is my first project involving any engine work so apologies for any obvious questions.

Per the chassis plate: Manufactured December 1971. Chasis number 202143. Engine number and transmission numbers all match.

Cylinder Head
-The head is stamped with "4" on the top. I could not find the meaning of this in a forum search.
-Looking at the underside and comparing to the Atlanticgreen.com head identification page, this appears to be an early Commando head (69-70). So not a combat head
-Obvious damage on one of intake valves, but no damage to the piston top that I could see.

Pistons
-The pistons are marked EX RH/LH and "+.060". This would mean the engine has been rebuilt, and that's about a far as you could go with an overbore, correct? So perhaps rebuilt multiple times?

My goal is to finish the bike as a (reasonably) reliable runner. Open to all advice on how I should get there. Thanks as always!

Check the size of the inlet port Combats and later were 32mm excluding 850 RH10

Good call. 28mm or so. Early commando head it appears.

Bikes near your serial number could be Combat or not. To be Combat, just means the skimmed head with 32mm ports, different cam (2S), larger carbs and maybe tank paint. They were making Combat and Standard at the time and if you order the factory record it won't tell you. So, when you get to the cam, if it's in good shape, it can determine which way to go. If the head you have cleans up and has no problem, I would make sure to have a standard cam and not call it Combat. On the other hand, you can find a Combat head, you can buy the correct cam and make it Combat pretty easy. You probably need carbs anyway and 30mm or 32mm cost the same.

Combats in 72 had the front disc brake, non Combats had front drum brake. It was a linked option so order disc brake or Combat tune and a disc braked Combat would be supplied. But front ends can be changed so its just another clue not 100% definitive.

It does have a disc front brake and a black cylinder barrel. Perhaps one of the pistons gave up at some point, resulting in a new head and the bore job.

The cam may be the ultimate confirmation

Cammy66 said:

Good call. 28mm or so. Early commando head it appears.

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Small ports is good. Don’t hog ‘em out …

Very difficult to tell if an original combat as these machines can have had many modifications over 50 years. It really doesn’t matter as if you want combat spec, build it that way. My ‘72 is an original combat and also built Dec 1971 with a bit earlier serial number. Look at the style of this original ID plate. If yours is not identical it probably has been replaced.

Those cylinders that are plus .060 are also pre ‘72 type. As I mentioned a lot gets modified over 50 years.

Cammy66 said:

Perhaps one of the pistons gave up at some point

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At 60 over its been rebored more than once, as they are not 72 barrels they must have been fitted after the original barrels broke or were out of rebores. So that engine has had a hard life and been kept going by using parts from other bikes.

Too bad it can't tell the stories it's had

kommando said:

as they are not 72 barrels they must have been fitted after the original barrels broke or were out of rebores.

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What identifies them as not being '72 barrels?