IS IT A COMBAT?

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parked

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Posted before to figure out the year and settled that it is a 1971.

20M3S/142515 - On the left front of the block
24347 - On the right rear of the head
C is stamped on the top of the head
It does look like there is another letter stamped in front of the ones listed, but whatever it is, it's barley visable.

Is there any way to tell if this is a factory commando combat or just a combat head that was put on. Engine build date ect
 
Combat production was supposed to have started at serial number 200976.
 
The combat engine has no sump filter screen and an "L" shaped breather at the lower back side of the left crankcase. The engine number you quoted will have a timed engine breather/hose coming from the left crankcase at the end of the camshaft. Sounds like you have a '71 engine that someone has added a combat head.
 
I thought the combat engine was entirely different, not just the head/cam.

I had a feeling that this bike was a race bike or someones mild street build at one point in its life. Was/is a combat head swap a common performance mod?
 
Also, what are the positives/negatives of the head swap? Does it effect reliability? Also, It still has twin amal carbs on it.
 
The Combat head is a high comression unit, partly due to shaving the head surface down. This results in different pushrod geometry if you use standard pushrods, just one issue. There are others, I'm sure.

Not sure if cylinder deck is also partially shaved, but the spacing of the lowest fin on the head and the highest fin on the cylinder is readily visible as a very small gap on a Combat, and a standardised gap width from top to bottom on the standard engines.
 
parked said:
I thought the combat engine was entirely different, not just the head/cam.
Click to expand...

Combat spec. was: high comp 10:1 head, 2S camshaft, 32mm carbs and manifolds.
Strengthened pistons were also introduced during Combat production.
 
Also, what are the positives/negatives of the head swap? Does it effect reliability? Also, It still has twin amal carbs on it.
Click to expand...

Not many negatives if done properly. The Combat head has 32mm ports where the original '71 head had 28.5 mm ports. The 32mm manifolds and 932 carbs from the Combat should be used. That being said, a friend of mine was having head gasket problems on his '69 'S' and we swapped a Combat head I had on the shelf to convince him he should have had the head surfaced. He stuck his 930s and small manifolds on it and was so happy he refused to give me the head back! I tried to get him to at least put the proper carbs for the head on it, but he wanted the "originality" of the 930's . Go figure!

With the extra compression you will probably find you will need to run premium fuel if you aren't already.
 
You have a 71 with a Combat head. I have a regular 72 with a Combat head. I have complemented this with a compression plate at the base, a 1.5" big bore exhaust and a 36mm Mikuni.
Complement, without a doubt, is the proper term!
 
pvisseriii said:
You have a 71 with a Combat head. I have a regular 72 with a Combat head. I have complimented this with a compression plate at the base, a 1.5" big bore exhaust and a 36mm Mikuni.
Complimented, without a doubt, is the proper term!
Click to expand...

I think you may have meant 'complemented'

Compliment - an expression of praise
Complement - to complete or make perfect
 
grandpaul said:
The Combat head is a high comression unit, partly due to shaving the head surface down. This results in different pushrod geometry if you use standard pushrods, just one issue. There are others, I'm sure.

Not sure if cylinder deck is also partially shaved, but the spacing of the lowest fin on the head and the highest fin on the cylinder is readily visible as a very small gap on a Combat, and a standardised gap width from top to bottom on the standard engines.
Click to expand...

Hi GrandPaul and all,
Since my engine has a few of the things that put it in the possible "Combat" range, I'm wondering even more now.
Black Barrels and silver head.
1972 Commando with Serial Number 204839. Date on red tag on steering neck: 1972 Feb.
After reading the above quote from earlier in the thread I went out and checked:
This is what I came up with.
IS IT A COMBAT?


What do you guys think? Is that gap small enough to assume a shaved head?
I can't seem to locate the infamous "C" on the head.
But then again, I don't know where to look.
It has 26,000 miles, so most likely if I'm lucky enough that it is a Combat, it must have had the superblend fix sometime in its early life.
Thanks ahead of time, and I'll try to be brave.......
 
Thanks Dave,
That location is underneath my headsteady.
I see in that picture its slightly cut away revealing the "C".

What does your gap look like?
Or the gap if that was somebody elses Combat.
thanks
joe dog
 
That "C" can be stamped anywhere from over the right exhaust valve to the center of the "V" to the very center of the head! It seems to depend on who did the stamping that day.
 
Parked wrote, "Is there any way to tell if this is a factory commando combat or just a combat head that was put on. Engine build date ect"

This could possibly be a combat motor. I think the only way to tell for sure is to check the lift of the cam. I did this with my early 72 with a 71 frame and a combat head, when I had the head off. I mount a dial indicator and figured it to be a stock cam.

I have a feeling that many early 72 had been assembled with the surplus of the 71 frames. Not to get off topic, cause I believe you could use the information as well, but how many of you out there has a 200xxx frame?
 
If the cam has a clean factory "SS" stamping (actually referred to as "2S") it should be a genuine cam.

Did I already ask this: Is there a bona-fide factory "Combat List" that lists the SPECIFIC Combats produced at the factory?
 
0.150"?

My 850 MkIII has less gap than that-and it's no Combat. :wink:
 
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