Combat engine or not
- Thread starter hamiltom
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hamiltom said:
Hi, welcome. You've come to a wealth of knowledge site for Commandos. We even have a guy that used to work at the factory posting here. Please fill out your profile, we'll know where on the planet you are, helps with advice/resources, etc. A picture of the '74 maybe? :mrgreen:
My 1973 Roadster(212494)has the Combat engine.I've heard before that 211110 was the last Combat produced.Pretty sure this bike was originally sold in England at Comerford's.#'s match frame etc.I've only owned the bike for 3 years and the guys at Big D Cycle in Dallas where I got it on an e-bay auction didn't have any history on it.Anyone ever hear of Combats produced after the 211110 vin?L.A.B. said:
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Does it have all the necessary engine parts that would identify it as being a Combat model (2S camshaft, 'C' head, etc.)?
212494 would seem to make it one of the late 1972 model series (212278-on) that had various 750 MkV ('73) spec. parts fitted.
212494 would seem to make it one of the late 1972 model series (212278-on) that had various 750 MkV ('73) spec. parts fitted.
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Norton dropped the Combat hot potato engine before end of '72 but no one knows for sure as even engine numbers don't tell whole tale. Its the 10:1 compression ratio with .040 shaved head and 2S cam and low rear breather 750 cases that make a Combat engine though 850's could be put to that spec with extra displacement. See if less fin spacing at head seam, low down breather hose for outside clues. I wasn't sure if my '72 just appeared to be a Combat outside so asked about the power band to be told it just gets better into redline instead of leveling out on pull. Combats about like other Cdo below 4500 then gets more rpm responsive till about 6800 can feel like another piston kicked in and many beside me had the front lift off surface some inches if daring to rev up that high on WOT though gears. A dial guage on valve and degree wheel on crank can ball park cam profile enough to see if 2S cam installed too.
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hobot said:
The presence of the "low rear breather" is irrelevant, as all standard '72 & '73 750 Commando crankcases had that breather.
The "High compression" RH6 head option used after Combat production ceased was also "shaved" but by 0.020".
Also, all Commandos traditionally have somewhat less of a gap between fins at the cylinder head to barrel joint, including the 850s, so simply stating there is "less fin spacing at head seam" is not a reliable way to identify a Combat.
birdman said:
32mm carbs would also be basically irrelevant unless all other Combat parts are present as the factory continued to fit 32mm carbs to most standard models after Combat production ceased.
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birdman said:
As I understand it, the initial Combat engine "detuning" process only involved replacement of the 2S camshaft with the standard item, and the fitting of a thicker (0.080" alloy) head gasket to lower the compression ratio. Approximately 1500 Combat spec. models were apparently returned to the factory for detuning, however the range of serial numbers these 1500 machines fall within is unknown I believe, and it is likely that some would have slipped through the net.
birdman said:
'211110' is mentioned in Norton factory Service Release N3/23:
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L.A.B. I clearly alluded to model variations with Norton using up what ever left over in bins on model changes so I'm not mis leading by stating the expected combination of more than one feature that must be there to earn Combat spec moniker. Like the ughly duckling story once matured a Combat spec Commando is the Cream of the Crop to me and a few others too. Anything beyond Comabt ain't really Norton.
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hobot said:
But you continue to allude that: "if it has a low down breather then it's a Combat"
...which does nothing but confuse the issue in my opinion, as the breather is not a Combat-specific part so regardless of other parts, its presence does not "make" it a Combat. The presence of the low down breather only identifies an engine as being a 750 from 1972-73 production.
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Duh LAB you are missing basic logic or just being annoying on purpose, as all Combat's cases have low down breather but of course not all case's with that breather are Combats, so its just one item to tick off the Combat check list. IIRC a few popular repair manuals show how to get Combat spec in other models even 850 by stage one modifications. Are they really Combats, nope not if they have turn signals installed and outside number series but should still perform like they should. Compression testing could give more clues until opening up to examine for sure.
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hobot said:
You could look at it that way but then I consider it's you who is the one being annoying.
hobot said:
Exactly my point, so you might just as well say that: "Combats have a gearbox", or "have a rear wheel", while it would be true to say that all original Combats would have those parts, so did countless other standard Commandos so what would be the point of mentioning it?
hobot said:
I disagree, it isn't a Combat-specific part therefore how can it be on the Combat check list?
hobot said:
I don't really know what this has to do with identifying a Combat?
Are you saying Combats didn't have turn signals? Or if fitted it's no longer a Combat? :shock:
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