Combat Question

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
16,886
Country flag
According to the INOA Tech Digest, Superblends were introduced in at S/N 207197.

The INOA Tech Digest 207197 number is incorrect as 207197 was when the change in housing diameter occurred.


"Service Release No. N2/6 July 1972

Explanation

Field experience with the 1972 models (incorporating two single lipped roller main bearings) indicates a small but significant premature roller main bearing failure rate. Reported failures have been confined solely to the one type of bearing.

Action:- When replacing defective roller main bearings, ensure the replacement is a Skefco double lipped outer, single lipped inner spool type NJ306, with a specified nominal internal diameter clearance of 0.0008" - 0.0012" (0.02mm - 0.03mm) prior to fitting . Ensure the crankshaft journals are carefully cleaned up, removing all signs of butts or scoring before fitting the inner spool. Models subsequent to Engine No. 207197 incorporate a nominal increase in bearing housing diameter to overcome any significant tendency to excessive closure of the single lipped outer series of roller bearing."

Note that "NJ306" is not the 'Superblend' as the original Superblend was the R&M 6/MRJA30. The later FAG 'Superblend' was the NJ306E.


"Service Release No. N2/9 August 1972
Explanation
In order to extend main bearing life, a change of roller main bearing specification has now been authorized and fitted on production engines from Engine No. 211891. The new roller bearing is designated 'Superblend' with an increased load carrying capacity and is supplied under Part No. 063906 (manufacturers part number R&M 6/MRJA30).

Action:- Where engine units are stripped for examination, or the need for main bearing replacement, fit only roller main bearings Part No. 063906 in place of the previously specified 063114. The new bearings are fully interchangeable, and should be fitted in pairs for maximum reliability.

More Superblend info.:
 
Joined
Jun 18, 2009
Messages
209
Country flag
Yes, the 1/4 mile thread has all the information about differences between standard 750, Combat and 850's. My experience was with my '71 750 that I had ported the head and milled .040 but left the cam stock and not 2S. I experimented with 32mm Mikuni twin carbs and it was quite impressive over Amals. Just wasn't a very good cold starter. Went back to Amals
None of my friends with 750's could keep up with mine even before I had done that work. I was a better mechanic than them, so points and valves were adjusted and timing set accurately.
A Barnett clutch and power shifting ended the life of my transmission, so I upgraded to a 5 speed and ended drag racing for the fun of twisties.
After purchasing a 850 with the heavier flywheel, lower compression & 20T sprocket, less impressive throttle response compared to a 750. I suspect 1/4 miles numbers were close as once the engine was up to launch rpm, the heavier flywheel made no difference.
I'm rebuilding the 750 and utilizing a Jim Comstock flowed head with a Webcam 312 grind with same compression ratio, so I expect I'll be feeling the Combat experience +1. I'll still use a 19T sprocket, I still want to feel the thrill of what the Norton acceleration is. Top end on the East Coast of the US is rarely experienced without ramifications :)
 

ILLF8ED

VIP MEMBER
Joined
Dec 30, 2003
Messages
3,122
Country flag
Year. 1972 (partly) although production probably began in late 1971 (no known date but supposedly from serial number 200976) and ended sometime around mid-'72 (at serial 211110).




Interstate and Roadster first, then Fastback. Not Hi-Rider.



Apparently not.



Black cylinder barrels and hydraulic disc front brake (although the disc brake was also fitted to post-Combat models).




Approximately +7.5% (UK prices) over the standard model (Std. Fastback) when introduced.




...Yes but the Norton management didn't or chose to ignore it.
Response to LAB comment about early prodution combats. I have owned two. 201123 was stamped Oct 1971 and my current 201881 is stamped Nov 1971.
 
Joined
Dec 22, 2006
Messages
5,840
Country flag
The quarter mile times in the big Norton Ultimate portfolio are all remarkably close, right from the first 8.9 to one 750 fastback , through the 10 to one Combats and early 850s.
The thing that all of the sub 13.5 second tests have in common is a 19 tooth sprocket. This seems to make more difference than the tuning variations, up to and including Mk1 850.
Once the Black caps went on, (some MK1A?) the bikes became very sedate. Combine high gearing with a restrictive exhaust and the performance is quite sad.
I recently tested restrictive silencers on the hill. They completely killed the acceleration, the bike actually slowed down while WOT!

Glen
 
Joined
Jun 28, 2009
Messages
1,702
Country flag
My first Combat had been re-engined with an 850 motor - the dent on the front of the gearbox cradle was a good indication why...
I put together a Combat spec motor for it and it was like my 850's angry little brother!
Apart from a slightly lumpy tickover it was still pretty tractable, but really lit up above 4k. Very addictive!
Every Jap owner needs to ride one, because they wouldn't believe how quick they are otherwise.
Naturally I fitted Superblend mains, and I'd also throw the following into the discussion:

The oil pickup at the front of the motor was a disaster, but easy enough to fix once the cases are apart. Not a big issue for regular use, but under sustained acceleration would prevent scavenging, drain the tank and then starve the big ends - a few 'how to' articles are available on how to remedy.
Standard pushrods are too long. The Combat head I bought had clear witness marks on the valve tips to show that the geometry was way off optimal.
I can't remember how much I trimmed off, but it was more than 40 thou.

With regard to identifying one, the skimmed head is quite noticeable, but the bigger giveaway is the larger inlet manifolds with 2 ribs only.
I'm not an expert, but this may also apply to some of the later 750's, but AFAIK, not in the '72 model year?

I have a Florida import Roadster ready to put together, and maybe I should pull my finger out and get on with it!
 

trident sam

VIP MEMBER
Joined
Oct 23, 2012
Messages
1,174
Country flag
The quarter mile times in the big Norton Ultimate portfolio are all remarkably close, right from the first 8.9 to one 750 fastback , through the 10 to one Combats and early 850s.
The thing that all of the sub 13.5 second tests have in common is a 19 tooth sprocket. This seems to make more difference than the tuning variations, up to and including Mk1 850.
Once the Black caps went on, (some MK1A?) the bikes became very sedate. Combine high gearing with a restrictive exhaust and the performance is quite sad.
I recently tested restrictive silencers on the hill. They completely killed the acceleration, the bike actually slowed down while WOT!

Glen

Yes, I did likewise and fitted a pair of restrictive black caps and they literally killed the bike, put the open ones back on and it's a different machine.
 
Joined
Apr 13, 2021
Messages
91
Country flag
I am always a little dubious of road reports in magazines and in particular their recorded performance figures.
When the quest for fractions of a second becomes important, so many factors are involved in getting the lowest possible figure that a degree of subjectivity is possible.
Magazines are profit making concerns and are beholden to their shareholders to maximise profits. By the mid seventies British bike’s advertising budget was very low in comparison to the big Japanese brands. I’m not suggest that the Norton’s figures are wrong but I’m sure every possible effort was made to get the very best times from brands that were running big advertising accounts with magazines.
Allow me to state outright that I have no direct knowledge of bike tests conducted in the Seventies, so to some degree I’m shooting from the hip. I do however have some very close (best friend) anecdotal evidence where a privateer’s excellent results (car) in a performance ’shootout’ against a big name supercar was downplayed when it was published.
The motoring journalist was apologetic when he explained that the advertising dollar was king.
As for factory performance figures, I think all makes exaggerated their claims and all sorts of tricks were used to reduce weight etc. As kids we joked about the physical size of the jockeys that the Japanese used in their acceleration tests.
Interestingly, intellectually I know that measuring the microsecond of a ‘quarter mile‘ time is no real indication of how good a bike is but a ‘mid twelve’ for a Commando still gets my blood circulating.
Finally, the 15 second quarter mile time recorded by the Mk3 in the 1975 Cycle World test mentioned previously seems very slow. Even allowing for the ‘middle-age spread’ of the Mk3 over early models, the required horsepower difference between 15 seconds and the lowest times recorded on earlier bikes seems beyond any difference in tuning.
just some thoughts
Al
 
Joined
Dec 22, 2006
Messages
5,840
Country flag
The 15 second time conversion is possible with any Commando model.
Slap on some restrictive Black caps and the bike will be gutless. A big CS sprocket will complete the conversion. I daresay that some Black caps even on Nigel's fire breathing Maney 920 would turn it into a scooter.
That's what happened to the MK3 and others fitted with those silencers. This was done to meet noise regulations. Funny thing, noise regs were a big deal back then. Now one sees straight pipe Harleys everywhere and its allowed.

The engine is a pump, if you partially block off the outlet it doesn't pump very much.
It's very cheap and easy to convert back to full power, most owners have done this.
The sound is a lot nicer too!



Glen
 

ILLF8ED

VIP MEMBER
Joined
Dec 30, 2003
Messages
3,122
Country flag
I had a non-Combat Commando motor that was quick enough to out-accelerate Honda 750's every time. I did have a 19 tooth sprocket in it, which might have been one the most important Combat performance item. The cam's high rpm impact coupled with the low gearing may have also been the biggest contributor to all those epic failures.
Back in 1972 one of my friends bought a Combat and threw me the keys. The acceleration was breath-taking to me at the time, but any Commando can get my blood pumping. No doubt somebody on this forum has had the pleasure of riding a Combat back to back with an 850. Could the difference really be that significant?
Yes I have. I switched bikes with a fellow club member….his 850 MkIII and my early combat. The difference is the combat feels very strong while the 850 is sluggish.
 

Mart UK

VIP MEMBER
Joined
Mar 11, 2021
Messages
185
Country flag
Feel like I need to defend my loved mk3 850! On the other hand, I don't have the std airbox, nor black cap mufflers. Also, I can't see how the starter could add 30lb. I've had the sprag clutch, starter drive gear and hydraulic chain tensioner in my hands. Be surprised if combined, that was much over a lb in weight. Can't see how the starter motor itself could weigh 29lb!? Maybe 5lb or so. Maybe a couple extra lb for a more powerful battery?

Maybe the RH4 head, or compression ratio damage performance. But I would guess most of it is the in/out breathing and gearing, which are more easily and usually fixed by now. Although, I have the bigger front sprocket and enjoy the rangey, loping pull and relaxed touring feel.

New years resolution, I'm going to lose 7lb from my midriff and keep the starter. :)
 
  • Like
Reactions: baz

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
15,764
Country flag
You gotta add up the whole… all the drive stuff in the primary, the starter motor, the primary case mods for the motor, the bigger battery, leads, etc, etc.

It’ll be close to 20lbs for sure. Might even be more.

But anyway the main thing on this thread is that it’s the black caps and raised gearing that are the culprits for performance MIA.

Yes the mk3 is heavier, but the stunted power and raised gearing must have combined to make it FEEL a lot heavier than it really was.

Regarding the black caps, I’d guess they’d have an even bigger detrimental effect on a Combat cos of the longer duration cam.
 
Joined
Jun 28, 2009
Messages
1,702
Country flag
A few of the American road test articles have made their way online in recent years, and make very interesting reading.
A lot of the road test bikes weren't just 'out of the crate' - one Commando had alloy valve collars, for example.
Brian Slark has an online presence (Facebook) and remembers taking a cylinder head to a tuning shop...
It's clear that quite a lot of journalistic effort was expended on establishing the 'stock' nature of the bikes, at least for some of the shootout type tests.
Whether the Jap importers played the same game or not isn't clear. One thing that does stand out is that in all the tests I've seen the Honda 750/4 comes out as a bit of a lame duck - right down the rankings for most attributes, and only saved from the bottom of the pile by a H***** D******* :D

Norton were clearly targeting the US Quarter Mile market when they launched (ahem) the Combat, but had to abandon it when the emissions regs strangled the 850s.
 
Joined
Apr 13, 2021
Messages
91
Country flag
Hi,
yes, the Honda 750/4 is an excellent bike to use as base line for performance motorcycling in the corst half of the Seventies. Although I’ve never owned one (not my cup of tea), I believe they provided bullet proof reliability and required nothing more of the owner than the ability to throw their leg over their rather high seat and press the start button, add fuel and service it according to Honda’s schedule. They were ’polite’, socially acceptable, asked little of the owner and had a ‘wow’ factor for those who knew nothing of bikes. The fact that a ‘blue blood’ bikey boy on a Commando might run rings around him point to point was largely irrelevant.
Interestingly, I have ridden a BMW 750/5 a bit in my youth and it seemed capable of surpassingly good performance with very low noise exhaust noise. It is a shame that British bikes could not have maintained their performance with a more subdued exhaust.
As for me as a kid, the louder the better
regards
al
 
Joined
Dec 22, 2006
Messages
5,840
Country flag
From the ET calculators, an extra 25 lbs is about 2 tenths of a second, not noticeable to most riders.
That's why we don't hear complaints of sluggish performance from owners of bikes retrofitted with e-starters.

Glen
 
Joined
Apr 22, 2020
Messages
798
Country flag
Well maybe they who don't complain about the added weight don't do a lot of hard braking or cornering, and wouldn't notice 50 extra lbs. ;)

What the heck is a black cap? Norton fashion statement?
 
Joined
Dec 22, 2006
Messages
5,840
Country flag
I love me some weight reduction from both bike and body, but it wasn't the 25 lb starter that caused the sluggish MK3 performance. Every MK3 road test I've read blames it on the incredible extra weight of the bike as compared to earlier bikes. Well it's not much really.
As Nigel says, the poor breathing would make it seem very heavy.
With the quiet pipes fitted, my MK3 felt like it weighed half a ton struggling up Dyno hill.
 
Joined
Apr 22, 2020
Messages
798
Country flag
That dyno hill test is a good one, but kind of rough on an old Norton. I'd have to hit that in 3rd at around 70mph. 4th at under 50mph would not be a fun starting point with my motor. It would be on the verge of lugging with the immediate incline unless it was full of race gas. It weighs less than an 850 by quite a bit too. It would recover, but probably not well enough to get in the dyno hill record book.

Black caps I guess are the disc looking plate things Norton stuck in the ends of the exhaust. I never liked that look (too much like something BMW did, or would do) and put it out of my mind. A Commando needs peashooters to maintain its dignity.

I could lose about 9 lbs, but I might need a time machine to pull it off.
 

ashman

VIP MEMBER
Joined
Jul 11, 2010
Messages
3,988
Country flag
When I decided to buy my 850 Norton new jumping on my mate's Honda 4s made that decision much easier I been riding Honda dirt bikes for a few years and we had a great Honda dealer in my local area but the top heavy weight of the Honda 4s, the 4 cylinder motor and the pissy sound it made out of the exhaust was enough for me and my mate gave me a ride on his hot rod 750 Commando/Featherbed for the day was all I needed to buy a new Commando and did my mates who all owned Honda 4s give me shit about it when I first pulled up on the Norton, but after running it in and learning how the bike handled they soon changed their mines when I left them for dead.
I was a light weight in my younger days, the 850 had the good mufflers on and it went well with a young 17 year old who was a light weight rider and a good rider as well, as for reliablity well the Norton is still going never let me down motor wise even being young and flog the shit out of it for the first few years of its life, but of course the Honda boys still put shit on me, but when I bought the Featherbed frame and started the conversion and built the motor for the Featherbed and built up the stock cam to Combat specs with port and head work and balanced crank with open mufflers was when it woke up my Norton motor, was like riding on rails and still does to this day, the Honda boys couldn't keep up with me in the ranges and tight twisty roads.
So building a 850 to near as close to Combat specs livens up a Norton and going with the featherbed frame and shaving a lot of weight off the bike made it my HOTROD Norton and still gives me a frill every time I ride it, its been my hot Commando/Featherbed and on the road since 1982 but with a lot more improvements done to it in the 39 years when I first built it, the motor has never let me down in all that time and it still pulls a good wheelie if I want to.
When I bought my 74 850 Commando in 76 they had all the M111s in the show room and the last kick start 850 sitting at the back of the room its was $1999 on the road and the M111s were $500 more, was heavier and the restricted mufflers but my mind was already made up to buy the last kick start model they had left, didn't tell anyone I was buying a new Norton till I pulled up on it, even the local Honda dealer was impressed as I still have my Honda dirt bikes.

Ashley
 

ILLF8ED

VIP MEMBER
Joined
Dec 30, 2003
Messages
3,122
Country flag
The ‘74 850 Commando I used to own had mufflers not only black cap, the whole thing was black.
 

Attachments

  • 9856F7AF-040C-45FF-B413-358019E24173.jpeg
    9856F7AF-040C-45FF-B413-358019E24173.jpeg
    108.2 KB · Views: 12
Joined
Apr 13, 2021
Messages
91
Country flag
God, but I wish I had of bought a JPN when they could be obtained for reasonable money. The sight of them still makes my blood stir. what a shame Norton didn’t put a bit more effort into the finish.
al
 
Top