Norton Commando 850 Interstate MKIII

 

 

 

 

Make Model

Norton Commando 850 MKII

Year

1975

Engine

Four stroke, parallel twin cylinder, push rod 2 valves per cylinder.

Capacity

829 cc / 50.6 cu in
Bore x Stroke 77 x 89 mm
Compression Ratio 8.5:1
Cooling System Air cooled

Induction

2 x Ø30 mm Amal concentric carburetors

Ignition

120W Lucas alternator

Starting

Electric and kick

Max Power

38.8 kW / 52 hp @ 6000 rpm

Clutch

Metal diaphragm clutch

Transmission

4 Speed

Final Drive

Chain

Front Suspension

Telescopic forks

Rear Suspension

Swing arm with Girling coil springs

Front Brakes

Single disc

Rear Brakes

Single disc

Front Tyre

4.10-19

Rear Tyre

4.10-19

Wet Weight

233 kg / 514 lbs

Fuel Capacity 

19 L / 5.0 US gal

Average Fuel Consumption

5.3  L/100 km / 18.7 kn/l / 44 US mpg

Standing ¼ Mile

14.4 sec / 145 km/h / 90 mph

Top Speed

185 km/h / 115 mph

Irony always accompanied the Norton Commando. Introduced in the late 1960s as a smooth and refined version of the traditional big British twin, its essential character was one dear to the heart of the enthusiast fond of the basic values in motor cycles. It was fast, lusty, lithe and light and virtues such as easy starting and quietness didn't fit into the conception.

The early 750 cc models were quick, with top speeds close to 120 mph and a combination of blinding acceleration and flexibility that has rarely been matched. Then the 828 cc models which were introduced in 1973 in an effort to improve reliability proved even better. They were tough, handled well and using Norton's patented rubber mountings for the engine and transmission were very smooth at high speed.

But the tough American noise regulations and a desire to appeal to a wider market spelled the end for the performance image. Three years later, the final form of the Commando, the Mark 3, appeared with electric starting, better comfort, disc brakes on both wheels and barely a whisper from the exhaust.

The irony was that when the Commando finally competed successfully against the Japanese competition in refinement, financial problems at the manufacturers, Norton-Villiers-Triumph, led to the end of its production in favour of the Triumph Trident, which was regarded as a more modern machine. The last Commando Mark 3 eight-fifties were completed in early 1977 while the Marston Road, Wolverhampton, factory was in the hands of the Official Receiver. The penalty that was paid for the civilized nature of those last Nortons was in acceleration. While the early Commandos weighed around 440 lb, the last Mark 3 versions tipped the scales at over 500 lb, enough to add a second to the standing quarter-mile times. With a time of 14.4 sec and a terminal speed of 90 mph it was little better than most 550 cc machines of the day.

The appeal of the Commando lay in its instant engine response. The layout of the engine and transmission with the 828 cc long-stroke parallel twin and separate four-speed gearbox was straight from the 1950s. Major differences were that the triplex chain primary drive had in the final form a tensioner and, as on the original Commandos, an all-metal diaphragm spring clutch.

The engine itself, with a bore and stroke of 77 mm by 89 mm, has a crankshaft with two roller main bearings and with a compression ratio of 8 to 1 was in a very soft state of tune. Developing 52 bhp at 6,000 rpm, it was as unobtrusive as an engine could be yet packed a punch from low revs that made the gearbox almost unnecessary.

The bike was still able to cruise comfortably and smoothly at 90 mph, but much of the old liveliness had been lost. Unlike the older eight-fifties, which would rev safely to over 7,000 rpm, the Mark 3 is at its best between 2,000 and 4,000 rpm. It pulls hard from 1,500 but beyond 6,000 the restrictive air intake and exhaust silencing cuts the power drastically. And there is no point at all in revving to 6,500 rpm.

Normally, such a lazy and relaxing type of power delivery makes a bike easy and undemanding to ride, and this is true up to a point on the Mark 3.

The four-speed gearbox complements the engine well and the drive is delightfully smooth, the rubber vane dampers in the rear wheel, added to ease the load on the gearbox, giving a snatch-free ride at no more than a walking pace in bottom gear. But the overall gearing is very high with a top gear ratio of 418 to 1. This, the optimum gearing for the engine, giving 6,000 rpm when the rider is flat on the tank at the top speed of 115 mph. At 70 mph, the unit is ticking over at a modest 3,800 rpm. The motor never feels that it is working hard, and there is never anything that could be called vibration at motorway cruising speeds.

However, the characteristics of the rubber engine mounting system made slow riding a chore. While the rubber units absorb the vibration at normal engine revs, an inescapable feature of the system is that it resonates at certain rev bands. On the Commando this is at 2,000 rpm. With the high gearing this occurs at 40 mph in top gear (a perfectly feasible speed for the torquey engine). The rider has to keep changing gear just to avoid the resonant vibrations. Fortunately the gear change is very good. None could be more creamy or positive in action, even though the lever has been transferred to the left-hand side of the bike.

Another poor aspect of town riding was a result of weak carburation, most obvious in throttle response where it showed as an occasional spit back through the two 30-mm choke Amal Concentric carburettors. The idling mixture control was near perfect, giving an excellent 500 rpm idling speed even after a brisk run; a period of slow running in town heated up the carbs enough to cause stalling. This was not the headache in traffic that it used to be just a touch of the green twistgrip-mouthed button and the electric starter spins the engine back into life.

It is not always like that - from cold, the Amal carbs still need messy flooding and the starter motor occasionally baulks at turning the engine over against compression without momentum from the crank's massive flywheel. And although we are assured of its normality, the crunching of the backfire-overload device when the engine stops sounds horrible. Such things are easily forgotten once you take the Commando for a cross-country spin. For like the Triumph Trident, the Norton Commando's handling is just great. The steering is neutral throughout the speed range and flicking into a bend needs no more than a nudge. Moreover, the bike feels absolutely secure when cranked over with the footrests lightly skimming the tarmac.

The other side of the coin is the poor ride quality of the stiff suspension. Small ripples are transmitted undiminished to the rider's hands and once caused the front wheel to step out in a bend. Only the bigger bumps are absorbed.

In this the Commando is no better and no worse than most contemporary bikes, although the deeper seat Norton use to absorb the bumps in fact spoils the comfort of the machine.

Without moving back the footrests to suit the long tank of the Interstate version (the test model), too much weight is placed on the rider's behind at speed and he wallows around on the padding. The seat cover is too thin, too, and under full acceleration the seat pan slipped and ripped through the material at the front.

Commando braking can be very good, especially now with the disc rear brake. The front brake lever is neatly curved to fit the hand and the power is immense. The rear unit was spoilt by an out-of-true disc and a leaking master cylinder.

Likewise the electrics of the bike are good with an exceptionally powerful 60-watt H4 quartz halogen headlamp offering a sharp pencil main beam and a well cut-off dip. The switchgear and controls are equal to anything on a Japanese machine. The clutch lever pull is light and smooth while all the necessary switches are in easy reach.

Maintenance has been eased on the latest 850, too, the most significant modification being the use of easily adjustable rubber engine/transmission mountings. Since the rear-wheel fork was mounted to the rear of the gearbox plates, excessive side play affected the handling adversely. This used to be adjusted for side clearance with steel shims - a very time-consuming job that brought criticism for the amount of attention it needed to keep the handling in trim. The final models used a much more sensible screw adjustment that requires the use of a small tool in the kit. It takes barely half an hour to set it up to taste, balancing vibrations from the transmission against handling quality.

The primary chain is adjusted automatically instead of moving the gearbox to tension the chain, and the rear wheel really is quickly detachable.

Overall fuel consumption averaged 44 mpg, but a tune-up and tappet adjustment (just like the old days) before the MIRA test session improved this to 51 mpg for the final tankful. Oil used improved to 700 mpp at 1,800 miles from new.

In its Manx Norton-type finish of silver with red and black lining, the Commando is as handsome as ever with plenty of polished alloy and chrome.

It is sad that production of the Commando was stopped so soon with such a loyal following of riders.

Road Test 1976