With the Cobra-Gold 2011 military exercise in full swing we can see some U.S. Marines riding around on interesting motorcycles. The thing is when the U.S. Marines get on the gas, it's not actually gas they're on. The modified Kawasaki KLR650 they use are running on the J8, the jet fuel used in everything from Huey Cobra helicopter gunships to battle tanks.
For years, the U.S. Military has tried to convert all its combustion engines vehicles and machinery to one dieselesque fuel to save cost, time and confusion. Hayes Diversified Technologies, a small company in Los Angeles. Started 30-years ago, by Fred Hayes and his sons have been converting Kawasaki KLR250s and, now-a-day, KLR650s. And they've been busy developing their own proprietary 'motorcycle' diesel engine.
The Hayes developed diesel engine uses some stock Kawasaki KLR parts, including the four-valve, DOHC valvetrain, clutch and transmission. But the major components – cases, cylinder, crankshaft, connecting rod, piston and cylinder head – are all Hayes design and production. Diesels require a narrow bore, a long stroke, a small combustion chamber and a huge flywheel. The Hayes diesel engine displaces 611cc and makes a claimed 30 horsepower at 5,700rpm and 44.74 Nm of torque at 4,200rpm. In comparison. Hayes claims its gas-powered 651cc version makes 58 horsepower.
Once astride the camouflaged saddle, the M103M1 JP8 feels like a very green Kawasaki KLR650 – until you hit the starter, that is. As in most diesels, there is an electric glow plug in the head to raise combustion temperature for cold starting. But once the engine is even slightly warm, it quickly rumbles into a slow, loping, slightly clattery idle.
Throttle response is very slow, according to one of the marines we interviewed. Which makes sense, because it has no throttle. As with other diesels, the wide-open intake tract always takes a full charge of air, to maintain the high compression needed to set off the fuel and air sans spark. Power is regulated, via traditional twistgrip, by the amount of fuel delivered into the combustion chamber, metered out by a conventional (for a diesel) mechanical fuel pump.
So a twist on the throttle grip results in … well, not much. It takes two to three seconds for the engine to respond at low rpm.
The big and heavy flywheel on the modified Kawasaki KLR has another notable effect: Once the engine gets spinning, you are going to move out, right now, when you let out the clutch. So for the first few kilometers, a new rider will lurch away from stops.
The current modified Kawasaki KLR650 is built without a counterbalancer to save weight and complexity, but latest M1030M2 versions has both counter-balanced and electronically fuel-injected. As a result, the current (M103M1) U.S military modified Kawasaki KLR650 shakes a bit more than a gas-powered KLR650 model.