Norton Commando Restoration Manual

Norman White

• Verlag: Crowood
• Jahr: 2020
• ISBN:
  9781785007606
• Thema: Design
• Thema: Design generale

The Norton Commando is a motorcycle with an ohv pre-unit parallel-twin engine, produced by the Norton Motorcycle Company from 1967 until 1977. With over 700 colour photographs, this book provides step-by-step guides to restoring every component of this classic bike. Topics covered include how to find a worthy restoration project; setting up a workshop with key tools and equipment; dismantling the motorcycle to restore the chassis, engine cradle and swing arm; restoring the isolastic suspension, forks and steering; tackling the engine, transmission, carburettors, electrics, ignition and instruments and, finally, overhauling wheels and brakes, and replacing tyres. There is also a chapter on the assembly of a restored 'Five Times Machine of the Year' motorcycle.

1	introduction

The 750cc Norton Commando was a hurriedly thought-up, designed and built stopgap machine produced to spearhead the newly formed Norton Villiers (NV) company. It turned out to be the only machine to be produced by NV in the company’s nine years other than a few P11 hybrids and the 650cc Mercury workhorse; and production of these ‘leftovers’ ceased in 1969. The big twin became arguably the most iconic British motorcycle ever produced. The bike was voted Motor Cycle News’ ‘Machine of the Year’ a record five times. Nevertheless, it was certainly not perfect and there were many pitfalls along the way. It was produced in around ten derivatives, all based on the same original concept.

In forming his new company, NV chairman Dennis Poore, a former racing driver and CEO of parent company Manganese Bronze, soon became aware that the machinery he had inherited from both the former Norton company and Associated Motorcycles amounted to a collection of tired and unattractive designs. At the forefront was an ageing and unpopular 750cc twin, the Norton Atlas, which was a stretched version of the far more successful 500, 600 and 650 forerunners. The big twin suffered teeth-rattling vibration, and lowering the compression ratio by fitting pistons with dished crowns barely alleviated the problem.

Poore began thinking in terms of something new, a flagship machine. In his wisdom, he successfully poached from Rolls Royce one of their prominent designers, Dr Stefan Bauer, followed by Austin Motors’ development engineer Bob Trigg and Bernard Hooper and John Favill from the original Villiers company. Tony Dennis, formerly the Woolwich drawing office manager, joined the design team.

In the interim, several new engine designs had been considered, none of which could realistically be adopted given the cost and time required in designing and developing a replacement for the Atlas twin. An ohc twin motor, designated the P10, showed little promise, so it was decided to continue with the Atlas engine.

Dr Bauer joined the company with no motorcycling background, but with his sound grasp of engineering he very quickly concluded that, despite its incredible racing pedigree and worldwide popularity with the motorcycling fraternity, the successful ‘featherbed’ chassis had to go, much to the surprise and chagrin of the old school. Believing the heavy tubular construction failed to lend itself to his task of smoothing out the inherent vibration produced from the big 360-degree twin, he came up with a radical new design, bearing little resemblance to its forerunners. A single 2¼in (57mm) main spine – in its original form, with gussets to stiffen the connection to the steering tube – formed a kind of inverted keel, containing any torsional or twisting tendencies. Suspended from this large tube via rubber bobbins and within a lightweight 1in tubular structure, the old motor was bolted to a cradle that included the primary transmission and gearbox. To isolate the rider from the expected vibration, it was decided to mount the engine and gearbox cradle on rubber bushes, located in a tube at the rear of the cradle and suspended on a ½in-diameter stud, which was supported in two lugs either side of the mainframe. At the front of the engine was bolted a further tubular construction also containing rubber bushes, this time suspended on a ½in bolt and supported on two more frame lugs. Abutments and shims were used to prevent lateral movement, and to maintain constant or near constant chain tension to the rear wheel, the rear fork, or swinging arm, was pivoted from the cradle as close as was practical to the gearbox output shaft and drive sprocket.

The rather radical new bodywork styling, complete with a large green blob mounted on the fibreglass fuel tank, and a similar green disc on the facia of each of the fork yoke-mounted instruments, was dreamed up by the established marketing wizards Wolfe Olins. The blob was intended as a brand mark from which the Norton could readily be identified, and green discs appeared on much of the advertising literature that followed.

The prototype Norton Commando, later christened the Fastback, made its public debut at the 1967 Earls Court Motorcycle Show, amazing the big crowds with its unorthodox styling. Two machines were assembled at the Norton Villiers factory at Marston Road, Wolverhampton by Woolwich development department personnel Eric Goodfellow, John Mclaren and Jim Boughen. The bikes were presented in silver livery, with a bright orange seat. Not everyone was impressed, but there was nevertheless something rather special about the new Norton. Making the most of the engine they had inherited, the team had cleverly tilted the motor forward, giving the impression of speed, almost as if the bike was in motion before it was even rocked off its centre stand.

Public response was overall fairly positive, and by March 1968 production was well underway, with the chassis fabricated at the Reynolds factory in Birmingham and engine and transmission components manufactured at the old AMC factory at Plumstead Road, Woolwich, where the machines were also assembled after the chassis were delivered from Reynolds. Each machine was road tested, and after any required rectification, the completed bikes were distributed to the growing number of UK dealers and – more importantly – the eagerly waiting North American market.

The New York-based Berliner Motor Corporation was initially chosen as the main US distributor, having previously handled the trickle of AJS, Matchless and Norton imports. Later, Norton Villiers set up their own west coast establishment, Norton Villiers Corporation, at 6768 Paramount Boulevard, North Long Beach, California. Sales began to increase dramatically, especially after the introduction of the Roadster and S type, the latter clearly intended to meet US approval.

In 1968, reports began reaching the UK of some machines with bent or cracked frame tubes. Woolwich development department engineer John Mclaren was despatched to Berliner to investigate. He soon discovered the problem was occurring before any of the bikes were removed from their crates. It was the practice of the packing department back at Plumstead Road to remove the front wheels and clamp the front end of the bike to the floor of the crate via its front wheel spindle. The wheel itself was packed separately in the crate. However, some handlers, when delivering the crates to their destinations without a fork lift, would shove the crates off the delivery lorry end first. The machines that crashed to the floor rear wheel first survived intact, but for some of those that fell front first, the shock was enough to bend the frame’s 1in-diameter front down tubes out of true. In some instances a small crack would form. A team was sent to replace the damaged frames but it was soon decided to return the remaining faulty bikes to the UK for remedy.

In late summer 1969, Norton Villiers relocated, with government assistance, to Andover in Hampshire, where a new factory was built. Conveniently, 5 miles (8km) west down the A303 was the Thruxton racetrack, which offered valuable testing facilities, and in due course the Norton Villiers development department was established adjacent to the recently remodelled race circuit. Named the Norton AJS Competition and Development Department, and run by Peter Inchley, who with John Favill developed the AJS Stormer motocross machine at the Villiers factory in Wolverhampton, the premises were shared with the AJS Stormer motocross facility.

One of the two prototypes assembled at Wolverhampton and pictured on display in Stockholm, Sweden in 1967.
ANDERS ‘NORTON’ LARSSON

The engine and transmission assembly moved to the Villiers factory in Wolverhampton. Delivered by lorry, the assembled engine and transmission units joined the assembly line in Andover. The completed machines were once again transported by lorry to Thruxton, where a newly formed Test and Rectification department just a stone’s throw from the Norton AJS unit was established. Here the bikes were oiled and fuelled up and fitted with dummy exhaust systems to avoid blemishing the chrome finish. Similar to the Woolwich procedure, each machine was run up, the ignition adjusted by stroboscope followed by the carburettors, then the bike was given a 10-mile (16km) road test and any faults remedied. The bikes were then loaded back onto the lorry and returned to Andover, where they would await despatch to the waiting dealerships. You might wonder how on earth they made a profit!

Officially named Fastback in March 1969,the bike was followed by numerous model variations including the R, which was basically a Fastback with conventional seat, mudguard and fuel tank; the S, with high-level exhaust exiting from the left-hand side; the SS, a street scrambler-styled machine; the Interpol police version; the Fastback Mk 2 and 3 with upswept exhaust and reversed cone silencers; the High Rider, which was a rather diluted attempt to attract the Harley-Davidson ‘Easy Rider’ fraternity, with high handlebars and a short seat with high tail. The Roadster, a production racer, the much maligned Combat, the Interstate with large 5-gallon (22ltr) fuel tank, a short run of club racing ...