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Norton Atlas

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Hello, six years after selling a Commando, I am considering buying another Norton.

How does the Atlas compare to the 750 Commando in terms of performance, handling, reliability and ease of maintenance please?

All advice gratefully received.

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Hi, last time I ran one, I would say vibration is the main difference. Lock wire every thing together, including exhaust collars, silencer bolts. I lost mine, and had to use high tensile bolts and lockwire. Later concentrics with rubber tipped needles stop frothing. Use 98 octane petrol. Apart from that, The usual old bike problems of previous bad maintenance, wrong parts, and of course wear and tear. Good handling, brakes in their day, leaky chaincases. Buyer beware as usual. I have one in bits for rebuild, lots to do, but a good one from an honest person would give you a summer rider. Happy hunting, Paul

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hello a good atlas with a well-balanced crankshaft  are very good the thing is the atlas has a better frame then the commando  and better on road-holding even at high speeds   even Bob Trigg said the Commando was a lash-up jobs  His words, not mine  But I bet with some work you get a very good ridable motorcycle out of an Atlas  you do know by 2022 they be 60 years old  Yours Anna J

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The Commando is a lot smoother though I find Atlas vibration levels perfectly acceptable. To me the advantages of the Atlas are its simplicity - no isolastics, simpler electrics and better handling. It's also a bit lower and lighter, particularly compared to a Mk 3. As with any bike, so much depends on the previous owner.  

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When new the Atlas was considered  a vibratory lump. Now that  virtually all have been fitted with high comp and heavier pistons your chances of finding a smooth one are minimal.However you CAN  build one. Lightweight pistons are availiable from the USA  and dynamic balancing is here. Its also possible to build a motor with different crank cam and ignition systems to make it feel like a vee twin . Featherlastic conversions have been built. That's the way I would go.

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Many of the magazines in the 1960's as well as the classic magazines have run road test on the Atlas. Real Classic did a in depth version a while back. The Atlas engine has a lot of torque, and are a great bike, that is if they are looked after.

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Hi again, difficult to say as T140's vary depending on year of crankshaft, and piston supplier. I have a new engine in my T140, and its not too bad. When I had a new Norton it was very bad for the first 12k miles, broke everything, but it turned out to be a commando motor with a different balance factor. The smoothest engine I had was a 1950 small bearing Triumph Thunderbird in 1966, lovely old sprung hub bike. The Atlas engine is often considered a step too far by many, but the same was said of the 750 Triumph engine, and Matchless G15 stretched motor that preceded the Atlas engine. Unless the engine is very tight, I would strip it and bring it up to date. Better the animal you have trained yourself. I think you would enjoy riding one, better handling than most sloppy old Commando's. Gosh, I hear the rustle of shock there! Later coil ignition engines are smoother! Try and ride a couple first, then decide. Best of luck, Paul

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My shifter is not engaging any gear...it’s in neutral now. Advice as to likely problem received with thanks.

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Can't comment on T140 but have a T120R 1972 which I assume is somewhat similar plus 1959 Dommie 99. I only potter on both maximum 50-60 but don't find the vibration on either unacceptable. I like the OIF as I find it perfectly balanced in terms of handling maybe because the oil tank is in the centre of the frame but may be psychological here. Obviously the Dommie has the featherbed, Both have not gone anywhere this year for obvious reasons so this is as I remember riding them. Regards, Hugh 

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For my Atlas engine, I have a set of Low compression dished BHB pistons, (cheers Anna), the crank will be re-balanced, Anna put it on her lathe and She stated the lathe tried to wobble!

The barrels will be re-sleeved to match the pistons and it will be stuck in a BSA or AMC  frame to make a Street Scrambler, a Rickman frame would be nice but.....!

To me there's no point tuning up a 750 twin for speed and performance, you want the flexibility of a mild cam, look at nature the more fierce predators, Little Owl, Weasel e.t.c are the small ones, so apply this to the mechanical and you start to get things right, if you compare the 88SS to the Atlas they are too completely different beasts and should be treated as such!

Harley Davidson and Indian got it right initially with a torque-producing, no need to change gear, under-stressed engines to lope along all day to cross the long straight roads of the USA. Africa, Australia and enjoy the view! In most  situations, (probably), as an all rounder the Vincent Rapide is a more useful bike than the Black Shadow, except in the boasting Bar room type situation.

After all why give the dentist money as your fillings are rattled out,  with a high-compression,  extra heat producing stressed  motor, when a low compression engine will give you no pain in the bucaal cavity at all and save you wasting your breath on bragging rights!

 

 

John

Hi Robert, just happen to be reading  "Rich Mixture" and in a chapter on Vibration Phil Irving proposed a parallel twin with a 76 degree crankpin spacing, this would allow one piston to be stationary whilst the other would be travelling at maximum velocity, this idea was suggested but none of the establishment & designers would take him up on it  at that time 1960s and it would have solved the 360 degree parallel twins problems of vibration frequencies!

...."with this arrangement the combined upward inertia forces will be halved and will be almost equal to the downward forces instead of being twice as great as with the pins in line..." 

On any twin with a three--piece crankshaft this would have been a simple task. The other advantage was although counter-weighting was still required there mass was much smaller.

Just shows what power, Edward Turner had! Probably also, Joe Craig, Bert Hopwood couldn't concede to a man, who was probably a better, more thoughtful engineer!

 

John

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"There are a number of these engines around"

Indeed, it is hard to find a modern parallel twin over 500cc that isn't.

The Donington 961, the modern Triumph Bone Vile range, the Enfield 650's to name but a few are all 450/270 crank motors. Interestingly, they all run balancer shafts too.

Even some V twins with a narrow angled 'vee' have staggered crankpins to make them behave as a 90° vee for smoothness. (not to forget HD patenting the "PoTaTo, PoTaTo exhaust note to try and stop others mimicking them too closely).

Funny how back in the 1960's, Honda CB72/77s had 180° cranks and journalists would praise them for their smoothness, but criticise the 'offbeat' exhaust note. Nowadays, with so many V-twins about, it is almost as if having a rhythmic steady beat exhaust note is so 'yesterday'. 

George.

 

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