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Bob Z. said:
Pictures of rear of engine?
Combat Motor
- Thread starter mrelmo
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Pictures of rear of engine?
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swooshdave said:
Many years ago, in the second edition of the INOA Tech digest, there was a mod listed that suggested that you drill two large holes in the timing side case (had a diagram), close off the small oval breather opening on the bottom of the case with a blanking plate, and attach a breather tube from the timing chest. That bike had the magneto blanking plate that bolts on, and that is where I made a new plate with a breather hose going to the oil tank. Back before Al Gore invented the internet, it was a popular mod - I discussed this with both Brian Slark and Phil Radford. Seemed reasonable. Now, anyone who has done this or the oil pickup mod, seems to get castigated in forums for anything that was done to these cases. It worked fine for me. Maybe if the CNW breather mod was available then, I would have looked at that as an alternative. As far as the "later edition 73 750" if you read DynoDaves post, it explains that late de-tuned 72s and 73 750s had the same cases, which are generally referred to as "Combat Cases". They still have the rear mounted breather, and this '73 still has that large hose.
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L.A.B. said:
Rear breather, no sump screen, first and only thin wall cam bearing 750, ID flat on the DS case, bevel block on the timing side bottom (plenty of others).
"Combat cases" and "Combat tune " does it for me. Two issues = 2 items to describe
What would you suggest as a name to describe the differences in the cases for all the world to be on the same terminology?
To me it is a definitely different engine configuration that would benefit from having a name...like 20M, 20M3S, Combat breather.
Confuse matters??? "Combat" alone is incredibly vague and we get to this stupid list of 10+ characteristics over and over, this and that and not the other. This thread is like a bad rerun that never goes away or gets clarified...IMO over 20 posts of mostly gibberish that could be cleared up in one or two intelligent posts. The original question from mrelmo is fine. But I see it as the blind leading the blind.
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dynodave said:
1972-on? 200000-on? I don't understand why there has to be this continual reference to "Combat" when many 1972 and '73 750 models that had those cases and breather were not Combats.
dynodave said:
Which is precisely my reasoning for not attributing the Combat name where it does not belong, and only serves to lengthen threads such as these.
What you can surely take from this and not much more is that it is probably a Combat Head. And, it is also likely that it is a 72 head on a 73 motor or a 72 motorcycle registered in 73.mrelmo said:
I can count what make a Combat on 4/5 of 1 hand.
Again,
1. The modified Head.
2. The camshaft
3. 32mm Amals
4. Front disk brake (sort of relative being common on most later 72's
THAT'S IT! Anything else was common to ALL 72's and assumingly some early 73's
I think most of all this BS is that people want to believe they are special and therefore more valuable. Oh, they're special alright, like the Olympics.
LAB, is there an estimate on how many Combat designations there were compare to all other during this time.
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pete.v said:
All we really know is that the majority of Commandos built during the apparent Combat production series from 200976 to 211110 especially those sent to the US would have been built to Combat spec. except for the Hi-Riders.
o0norton0o
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So......... if someone didn't know if they had a combat or not, I assume the only difference to them as an ignorant slob just riding their bike around and doing their own maintenance would be the different valve clearances between a standard bike and a combat. Correct?? And that would be entirely based on the combat having higher compression and the 2S cam??
Now let me ask, what is the average HP difference between combat and non-combat nortons? A few horses? 5 horses?? more???
Now let me ask, what is the average HP difference between combat and non-combat nortons? A few horses? 5 horses?? more???
o0norton0o said:
When you put it like that it seem rather unlikely that there are so many as LAB may have suggested, at least in the US.
As far as HP goes, it's not how much more, but more like where in the RPM range it is produced. If you get 5 to 10 more horse power, it will come closer to red line. Quite impracticle and rather dangerous. So why oh why do so many want one or two? I suspect this is due to a successful propaganda campaign that still lives in the minds of many.
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pete.v said:
Why? Does that date have some significance I should be aware of?
(If it had been revenge they would've just sent Hi-Riders. 
) o0norton0o said:
But if they didn't know they had a Combat-how would they know what the correct valve clearances should be? :wink:
o0norton0o said:
http://www.classicbike.biz/Norton/Broch ... ochure.pdf
"5 BHP" (65 BHP @ 6,500 RPM for the Combat)
L.A.B. said:pete.v said:
Why? Does that date have some significance I should be aware of?
The 2 wheeled bomb!
7/4/72 The 4th of July signifies the independence of the US from British rule in 1776. = Motive
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pete.v said:L.A.B. said:pete.v said:
Why? Does that date have some significance I should be aware of?
The 2 wheeled bomb!
7/4/72 The 4th of July signifies the independence of the US from British rule in 1776. = Motive
Yes, I think I do remember hearing something about that in a school history lesson, once. :wink:
I still think you would've been sent the Hi-Riders!
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The cam if checked to be a 2S, its listed lash is .008 In & .010 Ex looser than standard and if Combat spec 10 CR then the ignition timing will hurt your if much more than 28* full adv and factory pushrods should be shortened ~.040, though this applies to any Combat spec tune engine. It was a simpler era back then and the market that wanted British motorcycles were both sex and speed crazy in American so standards with drums were so not cool. Wes has a re worked after Bombed Combat in North Carlina and he gleams telling me he could our drag the 750 triple smoke till out of town and over the ton. If I was a betting man I would bet any 72 in America was the real deal. 1972 DS case inside has proud ribs fanning out from the ring around the bearing bore. My darn Trixie Combat sure wants to get me arrested as its pretty sane Commando up to 90 but then really gets too eager to go go.
o0norton0o
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L.A.B. said:
That was my point. Guys are asking about bikes with unknown histories. They see a "C" stamped on a head and a serial number. They have to wonder if they have a combat engine or just a combat head bolted up to their stock barrels and stock cam. I supose they could rotate the engine using a dial indicator and a degree wheel to try to determin what cam they have, rather than disassemble their engine to know for sure,... but they still face the dilemma of making a valve adjustment based on a letter stamped on the head and a serial number....
...but other than for the valve adjustment, you really wouldn't need to know if you have a combat bike or not, except for bragging rights of course.... 8)
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