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Not sure what pre-combat means. There are non combat machines before and after combat engines were available as well as during production of combat engines.
Norton engine numbers 1971
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Not sure what pre-combat means. There are non combat machines before and after combat engines were available as well as during production of combat engines.
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By pre -combat I am referring to pre 2xxxxxx engines ie with ball and roller bottom ends.. I thought, that all machines in 72 were fitted with Combat engines ,but could be wrong. There was a series of late 750s which did not have the Combat camshaft . These were reputed to be the fastest 750s. I think these had 32mm inlet ports.
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The 'production' Combats were from 200976* to 211110 and not all of those were Combats, for instance Hi-Riders were not Combats.
*(The Combat engine specification had apparently been optional since 1970 so 200976 wasn't necessarily the lowest numbered Combat)
Or Combat cylinder head.
Please provide evidence of that.
Yes, either in 'Low' (Std.) compression (RH5) or 'High' (but not as high as the Combat) compression (RH6) form.
The 30mm carb/head also continued into '73.
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"
Service Release N3/23
All 750 C.C. Commando models
Worldwide
Introduction of the current 32mm carburetter version of the standard Commando engine unit, replacing the previous 'Combat' specification (w.e.f. engine number 211110) has necessitated the introduction of two new cylinder heads which are listed below.
Interchangeability can be effected as shown, utilising the available range of cylinder head gaskets, in conjunction with the deletion of the cylinder base gasket where indicated.
Compression Ratio (Nominal)
Using 0.030in. Cyl.Head Gasket
With Cyl.Base Gasket ......W/out Cyl. base Gasket .... Identification
060988 Standard Commando 1968/72 (30mm) 8.9:1 .... 9.2:1 .... RH1
063327 Combat 1972 (32mm) ..................... 9.7:1 .... 10:1 .... RH3
064048 Standard Commando 1972/3 (32mm) 8.9:1 .... 9.2:1 .... RH5
064097 Standard Commando 1972/3(32mm) 9.3:1 .... 9.6:1 .... RH6
September 1972
"
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B+Bogus
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I have 152920, Dec '71, so I concur
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I was not aware that you could specify a Combat engine prior to 72.. ie with a 2s camshaft , different crankcases and twin roller bearing cranks. Yes you could order a production racer which may well have had a shaved head and a non standard cam - i thought it was what became known as the 3s.
These Hi riders with a non combat engine- I assume the factory was getting rid of earlier engines ,or where they the 2xxxxx
series cases and bearings but with a std cam?
060988 heads were not all 30mm inlets . Mine was only 28.5 mm . Perhaps at some point it was increased but mine is an October 71 engine so fairly late. Certainly they were fitted with 30mm carbs. Incidentally putting 32 mm 932s on mine gave it a much better top end.
I cannot provide evidence ie road test evidence for my statement 'reputed to be the fastest 750s ' but I think it comes from the article Tim Stevens wrote in Motorcycle Sport on the foibles of the Combat. It did not specify ,but one would imagine RH6.
Mark Savage
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You could specify a Combat engine prior to 72 as an option cost approx £56, but the crankcases would be not 72 cases and the spec was the performance spec at the time, so not the full 40 thou skin off the head but 20 thou. How many were made is unknown, if it was like Triumph homologation tricks then maybe 200 to be able to face in production class.
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There is no suggestion these early Combats had different crankcases (or twin roller main bearings). As the production series Combats supposedly began from 200976 then that's getting on for a thousand early '2' series that were apparently not Combats.
They would be 2xxxxx series engines at some point as 750 Hi-Rider production continued through '72 and into '73 retaining the standard tune 30mm carb engine.
http://www.classicbike.biz/Norton/Brochures/1970/72NortonBrochure.pdf
Also note when the brochure was printed the Combat engine was supposedly "optional" on the Roadster and Interstate, however, sometime during early '2' series production it would appear the decision was made to fit the Combat engine and disc brake to all Interstates as standard, for other models it was still optional.
"....the new Interstate, Norton's most powerful road bike."
"When the Commando Roadster is fitted with the Combat engine and the front disc brake as optional extras,......etc"
Yes, well, "30mm head" does refer to 28.5mm inlets.
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I was first aware of the Interstate at the January show in London of 1972. It was the first time certainly I heard the expression Combat. Prior to that you could specify an engine to stage 1 tune but I was not aware of it being called a Combat . £56 does not sound a lot of money now but then it was more than two weeks average UK earnings .I bought mine from a discount dealer , a previous years model with a £100 reduction in April of 1972. In April of 1973 a mate bought a discounted roadster
Presumably these were being discounted to make way for the 850s . It had a disk brake and a Combat engine. One would have thought that drum not disk braked models would have made their way to discounters
L.A.B many thanks for posting the sales brochures but I would treat optional with caution. Where any Interstates supplied with a non combat engine and drum brake? The disk brake was actually cheaper to make then the drum and more could be charged for it. I wonder when the last drum braked Commando was supplied. I was not aware of 30 mm heads and carbs being fitted to Hi Riders post 2xxxxx but it would make sense in a traffic light GP,or perhaps the factory had a stash of 30mm heads it wanted to use.
Presumably these were being discounted to make way for the 850s . It had a disk brake and a Combat engine. One would have thought that drum not disk braked models would have made their way to discounters
L.A.B many thanks for posting the sales brochures but I would treat optional with caution. Where any Interstates supplied with a non combat engine and drum brake? The disk brake was actually cheaper to make then the drum and more could be charged for it. I wonder when the last drum braked Commando was supplied. I was not aware of 30 mm heads and carbs being fitted to Hi Riders post 2xxxxx but it would make sense in a traffic light GP,or perhaps the factory had a stash of 30mm heads it wanted to use.
batrider
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When I bought mine in June 72 I originally wanted a Roadster with the disk brake but no combat engine. Was told no it only came with the combat engine. Was exchanging letters back and forth with Comerfords since probably March as one of the ride and export deals in the back of cycle magazines back then. Ended up with the yellow Combat 202093 with Jan 72 date. Had to replace cratered bearings at 4700 miles but been fine ever since. Most probs due to reading forums.
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Was it a 750 MkIV or MkV?
By 1973 (750 MkV) the disc brake would've been standard on all but the Hi-Rider.
Are you sure it was actual Combat spec.?
Combat production ended sometime around August 1972 (at 211110) and all unsold Combats in the UK were supposed to have been returned to the factory for "detuning".
I don't know but then prospective buyers would have been unaware of the Combat problems to come.
I don't know but it continued to be available into '73 and was standard for the 750 Hi-Rider.
http://www.etmoteur.fr/images/norton_commando_1973_interieur.jpg
The Hi-Rider wasn't exactly seen as a 'high-performance' model so it didn't need to have the higher powered (Combat or post-Combat 32mm head) engine?
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L.A.B. It was I think a 72 roadster mk4 purchased in the spring of 73 at a discount. Am pretty sure it was a Combat , in fact he was told that the factory had recalled their stock and changed the bearings . Whether this was so or not or just spiel is hard to say. Certainly it was ok whilst he owned for a couple of years and was faster than mine on top end .
As regards Hi-Riders, I never saw one in the UK,but acceleration rather than top speed would be thing and here 30 mm ports and carbs would come into their own .
As regards Hi-Riders, I never saw one in the UK,but acceleration rather than top speed would be thing and here 30 mm ports and carbs would come into their own .
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Comerfords were a very reputable dealer and they also discounted on previous years models , where you offered one ?
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If it had been returned to the factory for a "change of bearings" then it would almost certainly have had its Combat camshaft replaced and this is in the Tim Stevens Motorcycle Sport article you mentioned previously (nothing in it about the post-Combat models being the fastest, only that the gearing was raised so gave a higher theoretical top speed over the undergeared Combats).
Edit: However, he does say "..the rebuilt machines were quicker than the super-sports models on the same gearing." (but which)?
I doubt the average(?) Hi-Rider buyer would've been all that concerned about acceleration or top speed.
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It says: "The new gearing put 7,000 r.p.m. at 121 m.p.h., a much more sensible figure, as it could only be achieved with difficulty and a racing fairing. Unless, of course, the rider were to form himself into a streamlined shape and hide behind the filler cap."
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