A Cocktail from Kuhn
Customised Commandos make potent machines.
Jerry Clayton, Motor Cycle News, November 15, 1972
It used to be a favourite occupation a few years ago, for pseudo-racers to indulge in hairy blasts on Surrey's Kingston-by-pass. Racing was prematurely curtailed after some spectators at the underpass were seen to be wearing blue uniforms ...
More than a decade has slipped by since the age when rear-sets and clip-ons were "in" - really "in", but the Gus Kuhn Commando brings it all back to life.
The machine starts off as a standard Commando with front disc brake but is passed through the Kuhn tuning mill and given such refinements as a gas flowed head and 10.25:1 pistons.
The 30mm carburettors are changed for 32mm units, and the air cleaners are removed. These mods obviously pep up performance, but to cater for those looking for a good all round performance rather than an out-and-out road-burner that has to be kept on the boil, a standard cam is retained.
This softer cam has the advantage of providing a wider spread of power at low revs, making the bike really flexible so that it can be dropped into corners on the overrun right down to below the 2,000 mark and still be picked up without changing down.
I suppose that by having the standard rather than the Combat cam, one loses out on top end power, but really with a machine capable of over 110 mph in fifth gear, it's debatable whether the extra urge is necessary.
Possibly too, the acceleration would be improved with a Combat cam, but is a question of sorting priorities because the flexibility would be lost. As tested, the engine was a fine medium, and capable of holding its own with all but really hot big capacity road bikes.
The five speed gearbox is another extra. The box itself is faultless, but due to sloppy linkage, it was far too easy to miss gears when changing down, mainly between third and second. On two occasions I was more that grateful to take another squeeze on the front disc brake lever.
With the 20-tooth engine sprocket, the ratios appeared to be lower than standard, with the addition of a "super-cruise" fifth. The intermediate gears allowed one to reach peak revs quite easily before snicking into top, but it must be emphasised that the flexibility of the engine meant that the fifth gear was not simply treated as a form of overdrive.
Starting was simplicity - Commando style! Fitted with Boyer transistorised ignition, the engine would fire up at the least provocation. I found the procedure of flooding both carbs sufficient for all but the coldest mornings and when it was really cold only about half choke was necessary.
The main problem was that one needed a hefty swing on the kick-starter to turn the engine over - and 10.24:1 pistons don't help in this respect! By playing it cagey, however, and moving the kick-start lever round to improve leverage initially, the difficulty was reduced.
Considering the size and beauty of the beast, the horn seemed muted and somehow lost in the throaty roar that announced the approach of the Kuhn Commando. Certainly the very appearance of the machine - so racy and finished in bright red - was enough to draw the attention of other road users and pedestrians.
The only snag with such a machine on today's cluttered roads is other road users. People seem incapable of accepting that motorcycles do occasionally travel quickly. They display a complete disregard for the well-being of the rider, so much that apart from bumpy country lanes, where the riding position proved unsuitable, it took a round trip to an old haunt to assess the bike's potential.
The intriguing thought was: would the Kuhn be as quick as a rapid Triton I had once built? While I hate to admit it, the Commando won hands down.
Incidentally, the speedometer readings at 6,800 rpm were 48 mph, 65 mph, 79 mph, 96 mph and 110 mph at 6,500 rpm in fifth gear.
But not only in speed was the Kuhn machine superior, for returning at night was a far less haphazard affair with 12 volt lighting allowing one to travel in safety right up to the legal limit.
The Kuhn Commando is a newcomer of the old school. Gus Kuhn Motors allow you to take your pick from the speed-inducing goodies they offer to build a Commando based special of your choice. While a 19 tooth gearbox sprocket is standard they are able to fit 20, 21, 22 and 23 tooth sprockets, but more than 21 is not recommended for road use.
Those wishing to travel safely from A to B can mix their own Kuhn cocktail but the one tested would set you back a cool £873.
ENGINE: Parallel twin 745cc. Bore and stroke 73mm x 89mm with a compression ratio of 10:1, fitted with 32mm Amal concentric carburettors.
GEARBOX: Five speed unit by Rod Quaife.
SUSPENSION: Front telescopic fork. Rear swinging arm.
BRAKES: Front 10.7 inch disc. Rear full width 7 inch single leading shoe.
IGNITION: Boyer electronic.
CLUTCH: Diaphragm unit running in oil bath.
TRANSMISSION: Triplex chain primary, single row rear.
KUHN SPECIAL EQUIPMENT: (prices only applicable when buying a new Norton Commando): Glassfibre tank and seat £25, rearset footrests £14, clip-ons and lamp bracket £4, alloy wheel rims £25, close ratio gears 4-speed 4 pinions £24, close ratio gears complete set £40, five speed gearbox £90, GT fairing £19 (as fitted to test bike), full fairing £24. Stage One tuning: high comp pistons 10.15:1 and 32mm carbs £45. Stage Two tuning: As stage one but with special camshaft £80.