July 18, 2005 The concept of a diesel motorcycle is not one that has occurred to a lot of people – at least not many have thought about it for long because despite a rich century of innovation in motorcycling, only a handful of diesel motorcycles have existed and until very recently, they have all been utility vehicles – bikes designed to get great economy on fuel of questionable quality in rugged and remote regions and said diesel two-wheelers had no performance pretensions. As we all know, diesel technology has come a long way in recent times and now the sans-sparkplug engine promises a renaissance thanks to its low emissions, good power output and low consumption ... and like so many aspects of technology, it was the muscle of the military dollar that brought the world's first modern production diesel motorcycle into being.

In the utility area of diesel motorcycles, one marque seems to have been synonymous with diesel motorcycles –Royal Enfield– the marque manufactured diesel motorcycles both before and after its move from Britain to India, and as can be seen from this web page, people just seem to like the idea of shoehorning diesel engines into Enfield frames.

On top of that, one of the most utilitarian motorcycles of all time, the Russian Dnepr, is still offered with a HATZ-Diesel engine, and there is a small but enthusiastic group of diesel motorcycle enthusiasts who manufacture their own motorcycles using diesel engines of all types.

There’s also a strong following for the diesel motorcycle in Germany, some of which are producing impressive prototype motorcycles such as this Peugeot-engined Kawasaki. If you're interested in diesel motorcycles and developments in the area of diesel on two wheels, check out the DieselMotorcycles web site - a compendium of the very latest in the area.

Hayes Diversified Technologies (HDT) Kawasaki

But despite this strong groundswell of interest, there is currently only one modern production diesel motorcycle - a Kawasaki KLR650-based machine which is remanufactured with a diesel engine for military purposes in response to the new NATO requirements of "One battlefield fuel" with that one fuel being diesel. An initial order for 522 diesel motorcycles has already been placed by the US Marines and keen interest is being shown by the US Army, the UK Ministry of Defence and other NATO forces.

A unique technology partnership between Cranfield University and California-based Hayes Diversified Technologies (HDT) created the bike – the first bike of any kind with a purpose-designed diesel power unit.

John Crocker worked alongside project leader Dr Stuart McGuigan of the Engineering Systems Department, Cranfield University at Shrivenham, Oxfordshire to design the diesel power unit.

The challenge was to come up with a low technical risk design that was sufficiently light and powerful, and with an engine speed (RPM) range wide enough to give the level of performance required for use as a tactical vehicle.

John said: “The motorcycle also had to meet strict NATO requirements for all armed forces to operate their entire inventory of vehicles and powered equipment on either diesel fuel or aviation grade kerosene.

“This capability has major logistic advantages in obviating the need to carry other fuels to battle. And their lower flammability, in comparison with petrol, also greatly reduces fire hazards.”

The engine configuration is a liquid cooled, normally aspirated, 584cc (36 cu in) double overhead cam single with four valves per cylinder. Diesel fuel supply is through a special Fuel Injection unit and single injector developed specifically for the task and the Kawasaki-based combat bike produces a respectable 28 bhp at 5500 rpm with meaty flat power delivery from 1500 and 7000 rpm.

Unlike its gas-guzzling counterpart, the engine has multi-fuel compatibility and can use commercial diesel (inc low sulfer fuel), NATO Military Spec Diesel Fuel, Bio-Diesel (B20 or B100), Aviation Kerosene including JP4, JP5, JP8, and AVTR and plain old Kerosene.

And it’s a real 28 horses too – the bike recently set the world’s first land speed record for a diesel fuelled motorcycle.

Fred Hayes, founder of HDT, who was in the saddle at the world famous Bonneville Salt Flats , Utah, said: “The event was marred by rain the previous week and by poor track conditions, which limited the top speeds due to soft, wet salt. The bike was officially timed by the AMA at 85.466mph, against our calculated top speed of 86mph with production gearing. The calculated speed was at sea level (4350ft) on hard pavement. We’re delighted with the result. If we’d had an option for gearing and more track time, we may have broken the 90mph barrier.”

Fred does not rule out that the motorcycle may be made available for the consumer market. “Although the motorcycle is about 20-30% more expensive than a comparative conventional motorcycle, there would be cost savings for riders and environmental benefits in that the diesel motorcycle can do 110 miles per gallon - a little over twice the range of a conventional motorcycle,” said Fred.

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