The Oddball Norton 750 Commando
Strange turns in the evolution of the Commando line
The R, S and SS model Norton Commandos (from left to right).
Photo by Robert Smith
Engine: 745cc overhead valve, two valves per cylinder, air cooled parallel twin/56hp @ 6,500rpm (R model; 60hp @ 6,800rpm)
Bore and stroke: 73mm x 89mm
Compression ratio: 8.9:1
Carburetion: Two 30mm Amal Concentric
Electrics: 12v, coil and breaker points
Frame: Twin downtube cradle with Isolastic engine mounts
Front suspension: Telescopic fork
Rear suspension: Twin shock absorbers, adjustable preload
Front brake: 203mm (8in) twin-leading-shoe drum
Rear brake: 178mm (7in) single-leading-shoe drum
Front tire: 3 x 19in
Rear tire: 3.5 x 19in
Wheelbase: 1,441mm (56.75in)
Weight (dry): 181.5kg (400lb) (approx.)
Seat height: 787.5mm (31in) (SS; 800mm/31.5in)
Fuel capacity: 9.5ltr (2.5gal) (SS; 8.7ltr/2.3gal)
Top speed: 115mph (est.)
If market demand is today’s mother of invention, then opportunity is its midwife. Such was the case with the “R,” “S” and “SS” models of the 750 Commandos.
The late Sixties were a tough time for the British motorcycle industry. Buyouts and mergers were happening left and right, yet despite being the illegitimate child of a shotgun marriage between Associated Motor Cycles and Villiers, the Norton Commando became one of the most successful motorcycles ever produced in Britain.
Best known are the Roadster and Interstate models, built starting in 1971 until production ceased in 1975. But between the first Fastback Commando of 1968 and the final electric-start bikes of 1975, the factory built a number of short-run variants that are now highly collectible.
The R and the S
The earliest Commandos were made at the old Matchless factory in Plumstead, South London. When the Plumstead site was slated for redevelopment, assembly was moved in 1969 to a new facility in Andover, Hampshire (on the famous Thruxton circuit), while engine manufacture went to the Villiers factory in Wolverhampton, West Midlands.
Along with the change in location came an opportunity to tidy up the Commando engine. Principally, the ignition points were moved from a chain-driven jackshaft behind the cylinders (where the magneto had been on the 750cc Atlas) to the end of the camshaft to simplify the design and make the points easier to service. The tachometer drive, previously taken off the end of the camshaft, moved inboard, with the tach cable now coming off the front of the engine instead of the right side. The new Wolverhampton engine became know as the 20M3S, while production of the old 20M3 “jackshaft” engine stayed temporarily at Plumstead pending the plant’s closure. (The numbering scheme works like this: the 750 twin engine was Norton’s Model 20, and the Commando engine the Mark III version; hence 20M3.)
Page: 1 | 2
| Next >>