When the Marines requested a motorcycle that would run on JP-8, other military contractors proposed outlandish turbine-powered machines. But the Marines wanted a bike that would actually work, and soon, at a reasonable cost. Hayes won the contract.

The resulting HDT M103M1 uses the chassis, a few engine components and all the internal transmission parts of the Kawasaki KLR650, a workhorse capable of anything from daily commuting to Sahara exploring. But the Marine machine’s major engine components are all new, built for diesel service.

The difference was apparent the instant I thumbed the starter button. In place of the gasoline-powered KLR’s anxious idle, the Marine machine came to life with the low clatter of a London taxi.

In contrast to a gasoline engine, which responds instantly to the throttle, a blip of the twist grip resulted in  well, not much. It took a good three seconds for anything significant to happen.

On a half-hour test ride, the M103M1, though sluggish at first, gathered speed with dogged insistence. The footpegs and handlebars buzz as the engine revs  the counterbalancer that controls vibration in the stock KLR has been omitted to save weight and reduce complexity. Shifting through the five-speed gearbox gets the M103M1 past 90 miles an hour, a speed it will hold, apparently, until the end of time.