Almost from their beginning, motorcycles have been pressed into military duty, thanks to their all-terrain capabilities. However, this means supply chain problems—you have to keep them running, and since modern wars are won by logistics, a gasoline-powered motorcycle in a diesel/kerosene/jet fuel-powered military can be a source of frustration. About 20 years ago, one American company addressed this problem for the US military by building what has become a legend in the years since: The “Diesel KLR.”
Not your standard KLR650 engine! While the bottom end was basically the same, the top end was converted to run diesel, jet fuel or kerosene. Later prototypes also had the capability to run on gasoline, reportedly, but I’ve never seen one. Photo: Mecum Auctions
Family history
When this project kicked off, it was arguably the peak of the KLR650’s reign as a practical, affordable all-rounder, and Kawasaki already had a long history of providing bikes to NATO militaries. Specifically, Kawi had been selling the KLR250 to Canadian, American and other militaries and paramilitaries for over a decade, and those bikes had a good reputation. The US decided to use Team Green for its new project, but with a twist: The engines went to Hayes Diversified Technologies for conversion to diesel fuel.
The design work behind this project took a while, and it was highly publicized at the time—I recall at least two stories about it in Cycle World, maybe more. It wasn’t an easy job; Hayes Diversified Technologies re-used most of the standard KLR650 bottom end (same cases and five-speed gearbox), but replaced the top end with a liquid-cooled single cylinder that could burn diesel, biodiesel, kerosene or jet fuel, as per NATO’s requirements at that time—in wartime, support staff could simply re-fuel the bikes from the same jerry cans that they used for Hummers or deuce-and-a-halfs or whatever else was on-base.
The initial production run was made for the Marine Corps (or so I’ve read), but I’ve seen online mention of bikes that were supposedly built for European militaries.
Hayes mashed up Kawasaki parts, aftermarket bits and their own in-house components for this machine. Photo: Mecum Auctions
Mission accomplished
After months of tinkering, the diesel-powered KLR did indeed make it into production, with about 200 built, supposedly. The timing was perfect, as the War on Terror was just around the corner, and the American military had lots of opportunity to put these machines to test in The Sandbox.
Here on the home front, I think most of the motojournos who wrote early stories about the project had their enthusiasm dampened when they actually rode the diesel bikes. They were not fire-breathing, high-horsepower monsters. The converted KLRs made about 30 horsepower, even less than the already-underwhelming Japanese gasoline engine. However, the revised bikes had excellent fuel economy, and they had unbelievable torque for their small engines—every review I’ve ever read on these bikes has been absolutely in love with the massive pulling power.
- Photo: Mecum Auctons
- Photo: Mecum Auctons
- Photo: Mecum Auctons
Despite their low-hp performance, the Hayes bikes reportedly raced at Bonneville’s salt flats, where their unique powerplant would have probably qualified them for some silverware (not many bikes in the diesel single-cylinder category!). As for the fuel economy, the diesel KLR ran in Craig Vetter’s fuel economy challenges for years, in both streamlined and non-streamlined categories. The streamlined version was incredibly fuel-efficient. Fred Hayes (the guy behind Hayes Diversified, as you’d expect by the name… ) actually won a couple of the events in 2011 (results here, here) and again in 2012 (here, here, here). He won again in 2013 and in Vetter’s first challenge of 2014. Finally, at AMA Vintage Days in 2014, a gasoline bike took the top spot in the challenge, although Hayes wasn’t far behind in second.
All that competition was just for fun, and the real test of the bikes was their military service. However, with Hayes reaching an almost-unthinkable 162 mpg in his streamliner one year, it showed the practicality of diesel fuel in a motorcycle if you need a combination of torque and fuel economy—in his write-ups after the challenges, Vetter always praised Hayes’ creations for their real-world usability. They certainly had a lot more torque than the gasoline-powered Ninja 250s they competed against!
At one point, Hayes talked about civilian versions of this bike, but I’ve never seen one of those for sale either. Photo: Mecum Auctions
The Hayes Diversified Technologies bikes today
Over the past 5ish years, we’ve seen a few of these diesel KLRs come up for sale online, as the military gets rid of surplus vehicles. I don’t know if any remain in USMC usage or not. The bike in these photos is sold by Mecum as “is the last and known lowest mileage KLR decommissioned according to issuing SF-97 agency,” for whatever that’s worth.
Back before COVID, you could pick one of these machines up for about $5,000 USD on the surplus market. This bike goes for auction in Houston in April, and I wouldn’t care to place a bet on the selling price. These are extremely rare, and I suspect if the collector motorcycle market holds its value, the Hayes-modified machines will be worth quite a bit at some point. But that point could be many, many years down the road, and whoever buys this machine may get much more value out of just riding it, and enjoying it for what it is.
