Does an 850 Handle Better than a 750 ??

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worntorn said:
Would there be much difference between a 750 and 850 in weight?
Ive not weighed them but looking at the parts book for a 71 750 Roadster and a 73 850 Roadster there doesn't appear to be anything in it, save a pound or two on the strengthened swing arm and crankcases.
We weighed a 73 850 Interstate with added Alton e start. It was 4 lbs heavier than my MK3 Interstate, but the 73 Interstate fuel tank is larger than the MK3 version.
So the same weight +- a couple of pounds.

Glen
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Commando Weights from Factory Brochures (lbs.)

1969 Fastback 415 dry, S model 409 dry – From 1969 brochure.

1970 Roadster, S, and Fastback, 415 dry – From "Norton 1970" brochures.

1971/1972 750 Fastback, Roadster, Interstate, S, and Hi-Rider, 385-395 dry "dependent on style and equipment" – From "Frontrunners" and "Wild Bunch" brochure.

1972 Production Racer – 385 dry, 400 wet – From PR data sheet.

1973/1974 850 Roadster, Interstate, John Player, and Hi-Rider, 418 – 430 dry "depending on specification" – From "Superplus" brochure.

1975 Roadster, Interstate, Hi-Rider, and John Plaer, 460 dry – From "The Ultimate Ride" brochure.

Ken
 
It's really hard to know from the brochure numbers.
If the 1970 number of 415 dry is correct for a 750 Roadster and the 73/74 low number of 418 is correct for an 850 Roadster that leaves a difference of just 3 lbs. There were some strengthened items with the 850, 3 lbs might take care of those.
One of those items, the strengthened swing arm, did contribute to better handling for the 850. The MK3 got an even stronger swingarm, maybe another pound added but also a good step for better handling.
I think some have fitted the later swing arms to the earlier bikes for this reason?


I would have guessed that the common 750 models ( not PR) weigh about the same amount +-5 lbs as the same style kickstart 850 models.
The MK3 s seem to be heavier by about 30-35 lbs for the Estart mechanism and bigger battery. We more or less verified that the MK3 extra weight is starter only by weighing a friend's 73 850 with Alton. That came out at MK3 weight+-.


I need to hang another friend's stock 71 750 and 74 850 on the scale some day.
Bigger holes with the 850, could it be lighter? :)

Glen
 
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850 through-bolt Cylinders are a fair bit heavier than the 750 flange-mount ones. Not sure if the flywheel is heavier or not, but there's marginally more metal on the 850 crank.
 
Regarding handling and Commandos, they will always be inferior AT LEAST in stock form, due to the elasticity inherent in the isolastic system. That can be minimized ALMOST to the point of negation by 3-point rose joint limiting steadies. Of course most people know of the top steady replacement, the most common. A second, less well-known steady is Wendy Eads' front steady (I have one on my 880 monoshocker).

The third, and least-often-implemented steady is the lower/rear steady that DIRECTLY limits the rear isolastic's movement to fore-aft only. EVEN THEN, it is only ALMOST negating the overall movement, relative to the swingarm pivot point's relationship to the steering stem/headstock.

So, the Commando could possibly be a very nice roadracer, but never as perfectly able to give perfect handling, due to that inherent limitation.

(and none of this has ought to do with 750 vs 850)
 
Just some more fuel for the fire.

Commando Weights from Magazine Tests (lbs.)

I've tried to include only tests that appear to use actual measured, not the advertised, weights, but I'm not sure of some of them. Some of these weights are obviously not correct.

1968 750 Fastback 431 curb weight (with half tank of gas) – From September 1968 Cycle World.

1969 750 Production Racer 420 curb weight (half tank of gas) – From December 1969 Cycle World.

1971 750 Fastback 426 curb weight (half tank of gas) – From March 1971 Cycle World.

1971 750 Production Racer 406 curb weight (half tank of gas) – From January 1971 Cycle.

1971 750 SS 389 dry – September 1971 Cycle Guide .

1971 750 Roadster 419 curb weight (half tank of gas) – From March 1971 Cycle.

1972 Norton 750 Interstate 460 wet – From September 1972 Motorcyclist.

1972 750 Roadster 395 dry – From September 1972 Cycle Guide.

1973 850 Interstate 446 curb weight (half tank of gas) – From May 1972 Cycle World.

1973 850 Roadster 462 wet – From June 1973 Cycle.

1973/1974 850 John Player Special 476 curb weight (half tank of gas) – From December 1975 Cycle.

1973 850 Interstate 492 "Kerb Weight" – From October 1977 Bike.

1973 850 Interstate 466 dry – From May 1985 Classic Bike.

1973 750 Roadster 420 "Kerb" – From May 1988 Classic Bike.

Ken
 
I should add that the only Commando I've actually weighed myself was my grandson's somewhat modified MK3, at 460 (457.7, to be precise) lbs. full wet.

Does an 850 Handle Better than a 750 ??


Ken
 
grandpaul said:
I think that's a Mercury Bobcat "woody" station wagon, I had one! I WISH I had a Phantom...
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Not sure. I always thought it was a ‘74 Pinto, but hard to tell from the side. It got into the camera shot when I took this in 1976. I was at Hahn when Saigon fell in May ‘75 working in the dental clinic. We got a lot of POWs returning at Wiesbaden hospital during that time.
 
grandpaul said:
Regarding handling and Commandos, they will always be inferior AT LEAST in stock form, due to the elasticity inherent in the isolastic system. That can be minimized ALMOST to the point of negation by 3-point rose joint limiting steadies. Of course most people know of the top steady replacement, the most common. A second, less well-known steady is Wendy Eads' front steady (I have one on my 880 monoshocker).

The third, and least-often-implemented steady is the lower/rear steady that DIRECTLY limits the rear isolastic's movement to fore-aft only. EVEN THEN, it is only ALMOST negating the overall movement, relative to the swingarm pivot point's relationship to the steering stem/headstock.

So, the Commando could possibly be a very nice roadracer, but never as perfectly able to give perfect handling, due to that inherent limitation.

(and none of this has ought to do with 750 vs 850)
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As I understood it, the PR, '72 works JPN, the '73 Monocoque and the '74 Space Frame all had Isolastics! They could possibly have been very nice road racers!

The people riding them at the time seemed to think they were OK ;)
 
SteveA said:
As I understood it, the PR, '72 works JPN, the '73 Monocoque and the '74 Space Frame all had Isolastics! They could possibly have been very nice road racers!

The people riding them at the time seemed to think they were OK ;)
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I'm not arguing that point.

All I was pointing out is, there will always be SOME amount of flex.

Maybe that's not a bad thing?
 
Here is Dave Croxford's spaceframe, shot a few years ago at Barber. Hard to tell how the power unit is mounted from this.
Does an 850 Handle Better than a 750 ??
 
That might be an ISO up front, kinda hard to tell. Don't really see any other possibilities unless there's an underside unit aft of the primary. The swingarm does appear to be separated from the tubular frame. Could that be an ISO above the s/a pivot?
Does an 850 Handle Better than a 750 ??
 
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