Interesting 650 Norton prototype

Interesting..
Lots of questions, starting with.
1. Where's the cam or cam's?
2. Does that rocker assembly depart from the head?

Isn't this Anthony Curzon's bike? Isn't he capable of mending it anymore?

- Knut

Anthony does not have an equiped proper workshop , just storage .And grass. This bike is not factory built ,There was no blueprint or parts list. There will always be compromises made and things to be improved , Paul has the time and facilities to sort out some glitches. With luck i may get to ride it and post my impressions .

Ive confirmed from Paul there is no isolastic mounting.will ask him how vibration compares to other higher displacement twins he has ridden. Might be one reason why Norton did not move this on to producrion line.

I must first admit that that I know almost nothing about that engine so the following is pure speculation.

It is a late 50’s engine so it is fitting that it is shown installed in a 50’s frame. The mid 60’s effort was the P10 DOHC design.
To cut costs the cam and points chain drive assemblies were eliminated by driving the camshaft directly off what is the intermediate sprocket position on the Domi engine. That is the reason for having the camshaft at the rear of the barrels. The points are driven off the camshaft like the later Commandos.
The cylinder head is clearly a modification of the pre-650ss Domi head and concentric carbs didn’t exist.
Clutch and most of the gearbox internals will be the standard AMC items of the day.

That’s it folks, time for bed then I have to make some hides to shoot from at those pesky squirrels that keep pinching all my hazelnuts.

Vibration is not the problem with the rigidly mounted motor, if the crank is balanced for high revs. The problem is the high balance factor causes the bike to move backwards and forwards when the motor is idling. A HondaCB750 does not do that. My Seeley 850 does not vibrate at any revs - but when idling, it is embarrassing. Market-consciousness must be important when selling motorcycles, but I like an adrenalin rush. I would really like to give a few of you guys a ride on my motorcycle - you would love it.

What are the advantages of a unit construction? Simplified assembly/machining? Weight saving? Structural strength/ridigity?

Tornado said:

What are the advantages of a unit construction? Simplified assembly/machining? Weight saving? Structural strength/ridigity?

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Less weight of eengine and frame, less material required, reduced number of fasteners, improved reliability (geared primary drive), better weight distribution of bike (engine can be moved forward in frame), improved heat management.
This translates to a better handling bike, lower manufacturing costs, and less maintenance required.

- Knut

Head is nothing like any other Norton head has features more like AMC/Triumph but no common parts , Yes its a vibrator but was geared far too low . Better geared now but has never been dynamically balanced with piston weights . Crank made locally . Valve timing and ignition curves are based on Long stroke Norton settings so probably wont be the best for a short stroke , These things would have been optimised with developement by the factory if the project had been accepted and passed by AMC ( it was rejected just because of petty internal Norton/AMC politics ) . And we got the Atlas motor with small (by comparison) iffy mains, flexy crank .,Offset barrels and weak transmission designed for 30HP instead. This motor , or a developement of it , should have powered the 650SS Atlas and Commando .

Norton were a small company making an insignificant number of bikes compared with Triumph & BSA. They did not have the capacity properly to develop more than one design at a time and with AMC dominated by Matchless/AJS, too much attention was focused on trying to keep those going rather than throwing everything at Norton.

hybridracer said:

Norton were a small company making an insignificant number of bikes compared with Triumph & BSA. They did not have the capacity properly to develop more than one design at a time and with AMC dominated by Matchless/AJS, too much attention was focused on trying to keep those going rather than throwing everything at Norton.

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Very true
I think sometimes people forget just how small Norton were by comparison

baz said:

Very true
I think sometimes people forget just how small Norton were by comparison

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Makes me appreciate what an even smaller maker achieved, without ever merging with others...Velocette hung in there run by a family, turning out at most several hundred bikes a year, until 1971...paying off all creditors before shuttering forever.

Tornado said:

Makes me appreciate what an even smaller maker achieved, without ever merging with others...Velocette hung in there run by a family, turning out at most several hundred bikes a year, until 1971...paying off all creditors before shuttering forever.

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Let us not forget the Viceroy scooter, a mistake from which they never recovered.

norton bob said:

if the project had been accepted and passed by AMC ( it was rejected just because of petty internal Norton/AMC politics ) . And we got the Atlas motor with small (by comparison) iffy mains, flexy crank .,Offset barrels and weak transmission designed for 30HP instead. This motor , or a developement of it , should have powered the 650SS Atlas and Commando .

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You are wrong. The unified twin project wasn't rejected, on the contrary, Matchless at Plumstead was very much in favour of the project. The main issue was, Norton (Birmingham) was much too late completing the design. If my memory serves me, it wasn't before 1962 that drawings were handed over to the design department at Plumstead for review, calculation, production readying, tooling design, etc. By this time AMC was fighting for it's existence, and the concern's economy didn't allow a costly venture like preparing a completely new engine. So, the management deferred the project by one year (for the 1964 model year). By this time the design was already outdated (it would have been acceptable for 1958, but at that time AMC was busy churning out the lightweight Norton unit twins and their own single cylinder lightweights). Influenced by Honda, by 1963 management was foresighted and chose a DOHC twin as development basis, still re-using many of the unified twin's design concepts. For the design work, AMC relied too much on one man (Charles Uddal), whose personality appeared to be both proud and un-cooperative. His engineering skills were probably insufficient for this monumental task. What AMC should have done was bring in an outside consultant, perhaps a Japanese or a German. Unfortunately, there was a bit of "not invented here" mentality at Plumstead, especially after the Piatti mishap in the factory's venture for making 2-strokes in the late 50's. This latter venture is another example of a designer who was given too much say.

- Knut

Classic Bike, Sept. 2004 presents the engine and the incarnation in a Featherbed frame.

- Knut

Norton were primarily interested in racing, and their bikes reflect that. They sold road bikes to finance their racing. A Norton was usually a real motorcycle. The 1960s was the space age. Unit construction engines leak less oil. However a unit construction Bonneville handles better than a preunit Bonneville. I think it was mainly due to steering geometry. A Commando 750 is a detuned Atlas 750. It is a different mindset - the Honda CB750 gave Norton a fright. I rode a CB750 when they first arrived - to me, it felt like riding a brick. But I was used to bikes which handled. There are two mentalities involved - fast in a straight line - or fast in corners. Some people die in the bum when they are blown to the weeds in a straight line. Two-strokes were faster, but could often not accelerate when in a corner - they usually had to be upright and pointed. Reed valves changed that. Most race circuits are half corners and half straights, but public roads go on forever. So you need a different motorcycle. It is all about having fun.

acotrel said:

...A Commando 750 is a detuned Atlas 750...

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A Commando is a highly tuned Atlas 750. FIFY.

acotrel said:

Norton were primarily interested in racing, and their bikes reflect that. They sold road bikes to finance their racing. A Norton was usually a real motorcycle. The 1960s was the space age. Unit construction engines leak less oil. However a unit construction Bonneville handles better than a preunit Bonneville. I think it was mainly due to steering geometry. A Commando 750 is a detuned Atlas 750. It is a different mindset - the Honda CB750 gave Norton a fright. I rode a CB750 when they first arrived - to me, it felt like riding a brick. But I was used to bikes which handled. There are two mentalities involved - fast in a straight line - or fast in corners. Some people die in the bum when they are blown to the weeds in a straight line. Two-strokes were faster, but could often not accelerate when in a corner - they usually had to be upright and pointed. Reed valves changed that. Most race circuits are half corners and half straights, but public roads go on forever. So you need a different motorcycle. It is all about having fun.

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Why on earth to you keep repeating the same utter bollocks about a commando being a de tuned atlas?
What is wrong with you?
This is a serious question?

Cue mindless rambling about balance factor with a complete lack of understanding of how the isolastic system functions with respect to balance factor.