Given the number of off-road bikes in use around the world, you'd think two-wheel drive would be the Holy Grail of the motorcycle industry, but no mainstream manufacturer has yet offered such a bike to the public.
The steering geometry of a motorcycle makes it almost impossible to transfer power mechanically to the front wheel and, although both Yamaha and KTM have patented systems using a hydraulic motor in the front wheel-hub (and run them successfully in competition), this creates as many problems as it solves.
The hydraulic motor adds a lot of unsprung mass just where you don't want it, needs two very high-pressure flexible hoses which are vulnerable to damage - and then there's the problem of getting both wheels to cover the ground at the same rate.
The front wheel of an off-road motorcycle is much larger than the rear, so just synchronising their revs (not terribly difficult with today's electronics) won't work. Plus you need a differential of some sort because the rear wheel of a motorcycle travels further (ie faster) than the front in cornering.
Yet there is one motorcycle, designed from the ground up as an all-wheel drive vehicle, that's been in series production since the1960's. It has no hydraulics (or suspension!) and it's insanely complicated, but it works, and has done for nearly 50 years without major changes.
In the late 1950's a California inventor called Charlie Fehn built a prototype "two-wheel drive mototractor" using a chainsaw engine, a tubular-steel frame and two small tractor wheels. It looked silly but it would go up the steep side of a sand dune without hesitation and his wife took photos of him doing just that as proof.
By the late 1960's the Rokon company was mass-producing Fehn's weird little motorcycle and continues to do so today. They're not officially imported into South Africa but a few have come in privately, and I was recently offered the opportunity to ride this one, a 160cc Ranger.
The current Ranger, introduced in 1994, was Rokon's first four-stroke model; it has a single-cylinder Honda industrial engine (complete with pull-the-string recoil starter!) that develops four kilowatts at 3900rpm. It drives a three-speed transmission via a torque converter - and that's where it starts getting complicated.
You shift gears by pushing or pulling a plunger on the side of the bike - and a sticker on the casing warns you not to try doing it "on the fly". So you stop, get off and stand next to it, every time you want to change gears. This is not as big a deal as it sounds since the Rokon will happily pull away in any gear.
Rokon says the Ranger will do 16km/h in first gear, 35km/h in second and 45km/h in top. In the real world, without a speedometer, that translates to very slow, even slower and "I could walk faster than this!"
The gearbox drives a cylindrical transfer case ("mitre box" in Rokonspeak) which has a sprocket at one end, a tiny, cable-operated disc brake at the other and a shaft drive in the middle.
The sprocket drives the rear wheel via a chain while the drive shaft goes up the inside of the frame's large-diameter backbone tube, through an inline coil spring that will allow the front wheel to turn slower than the back but not vice versa, and a universal joint in the steering head, to a similar mitre box directly over the front wheel and from there via a chain to the front wheel.
The only suspension is a spring under the saddle and the fat, low pressure (0.24 bar!) 5.9 x 12" tyres, and the only electrical system an 88-watt transistorised magneto powering the ignition, a headlight and a tail light and no, Cyril, it's not street-legal.
The powertrain is mounted high off the ground in a very robust, welded tubular-steel frame; the only parts protruding below the frame are the footpegs, which swivel out of the way of any obstacle to increase the Ranger's ground clearance to a mind-boggling 375mm.
The air filter intake and the Forestry Service-approved spark-arrestor tailpipe are mounted high in the frame; Rokon says the Ranger will wade through water 600mm deep without missing a beat and, at a claimed 1.4 litres an hour, the thick-walled, 10-litre plastic fuel tank will keep you going all day.
Riding a Rokon is deceptively simple: make sure the transmission is in one of its two neutrals, yank the cord of the recoil starter until the little pushrod engine rattles into life, bang the knob into gear, get on, open the twistgrip and away you go.
It's mechanically noisy (not surprising, given the complexity of the transmission) and quite a lot of vibration comes through the footpegs and handle-bars, although very little reaches the rider through the thickly padded, sprung saddle.
Riding it on the road is a bit nerve-wracking; cyclists and kids on rollerblades yell at you to get out of their way and you realise that, with a seat height of only 760mm, most car drivers can't see you.
But that's not what it's for.
As soon as you hit the dirt the Ranger comes into its own; the ride is much less intense because the hard-working little engine isn't running flat out all the time. It's very stable and the steering is quite stiff, thanks to the driven front wheel, so you can relax and look around you, pick your way around and over obstacles and not worry about accelerating uphill - this thing doesn't even notice hills.
Rokon claims the Ranger will climb a 58-degree slope; that's way steeper than one-in-one and that's how I nearly got into trouble. I parked the bike halfway up the steepest slope I could find and slithered down to take the picture alongside - but then I couldn't climb up to get back on!
Eventually I had to walk the long way round to the top of the ridge and climb down to the bike, which pulled away without fuss - in second! - and rattled away over this and any other obstacle I tackled, at not much more that walking pace, but seemingly unstoppable. You can't even fall off it; when the going gets really rough you just put your feet down and paddle along.
Charlie Fehn had one more trick up his sleeve, way back in 1959.
Our test Ranger had the now-standard welded-steel rims but Fehn's prototype ran on hollow "drum" wheels fabricated from aluminium sheet, which are still available from Rokon as accessories.
Empty, they contain enough air to keep the 93kg Rokon afloat (on its side, true, but afloat) or you can unscrew the filler caps and pour in enough petrol to keep you going for 800km - that's about a week of non-stop riding at Rokon speeds.
A Rokon is not so much a motorcycle as a two-wheeled Unimog, a vehicle that (literally) goes its own way over any terrain, scorning such luxuries as trails or even footpaths.
For thousands of Americans who work - or play - in the Great Outdoors, it's a passport to places not even a horse could take them, and certainly nothing else on wheels.
Engine: 160cc fan-cooled four-stroke single.
Power: 4kW at 3900rpm.
Induction: Horizontal butterfly carburettor.
Ignition: Transistorised magneto.
Clutch: Torque convertor.
Transmission: Three-speed plunger-operated gearbox with shaft and chain drive to both wheels.
Front Suspension: None.
Rear Suspension: None.
Front brake: Cable operated disc brake on mitre box.
Rear brake: Cable operated disc brake on mitre box.
Front tyre: 5.9 x 12 tubeless.
Rear tyre: 5.9 x 12 tubeless.
Seat height: 760mm.
Dry weight: 93kg.
Fuel tank: 10 litres.
Top speed (claimed): 48km/h.
Fuel consumption (claimed): 1.4 litres/hour Price (Used): R25 000.
Bike from: Biketique, Cape Town.