Tech Matters - Shop Talk

Can't You Hear Me Knocking?

Is there a diesel-powered motorcycle in your future? A few years back I'd have said absolutely not. Now I'm not so sure. What changed my mind? Two things: The first is that fuel prices have shot through the proverbial roof, and the second is that in recent years, as anyone who's witnessed Le Mans' winning 650-hp Audi R10 in action can tell you, high-performance diesel technology has gotten very, very good.

What makes diesels most tempting is their penchant for fuel economy. On average diesel engines are roughly 35 percent more fuel-efficient than their gasoline-powered cousins, and better yet, they aren't particularly sensitive about what you feed them. For the most part biofuels work just fine. In fact Rudolf Diesel's first experimental engines were powered by peanut oil, so the twin attractions of economy and the ability to burn an easily renewable fuel makes the diesel engine an interesting proposition in these days of nosebleed-high fuel costs. I should also point out that diesels require relatively little maintenance and are reliable to a fault, which helps offset their higher initial purchase price and may make them appealing to riders who rack up lots of mileage.

Those of you with a passing familiarity with diesels are probably thinking-mileage and reliability aside-"Aren't diesels heavy, low-horsepower lumps that are loud, smelly and best suited for plowing fields and lifting heavy loads?" Well, yeah, they can be, especially the older ones. However, tightening noise and emissions laws as well as economic factors have forced diesel manufacturers to ramp up efforts to resolve those issues. The results-achieved partly by going to lighter materials, such as aluminum in engine blocks, and partly with enhanced technologies like computer-controlled common-rail injector systems that better manipulate fuel delivery-have paid off handsomely. The latest generation of diesels, particularly those in cars and light trucks, are civilized, relatively clatter-free, and display surprisingly good performance.

As I mentioned, Audi has been in the forefront of racing diesel development, but BMW, Alfa Romeo and Mercedes have also built winning race cars using diesels-and yes, they do compete against gasoline-engine cars, and quite successfully.

While there aren't a whole lot of folks currently building diesel-engine motorcycles, there are enough to get my attention. In the U.S. a company called Hayes Diversified Technologies builds a diesel version of the Kawasaki KLR 650 for military use. The specs are impressive: The bike gets a reported 100 miles per gallon, makes decent if not outstanding power, and has some serious low-end grunt. People who have ridden the bike say it's a little pokey, but not bad when compared with the OEM gasoline-engine version. HDT was working on a civilian version that was expected to retail for around 19 large. The project has reportedly been put on the back burner, 19 grand presumably being a little more than the average dual-sporter wants to spend, even if he'd be getting 100 mpg.

Of greater interest are some of the projects being undertaken in Europe. The feeling there is that in the next five years or so the gasoline engine will have reached the limit as far as reducing its emissions, so the only way to meet expected standards will be by increasing mileage. Because diesels offer so much promise in that area, several manufacturers have been spending serious time and money trying to refine a diesel-powered bike. Among them are rumored to be BMW, which is reportedly testing a boxer version in northern Canada.

Another German firm, AVL, has proposed building a 1330cc, three-cylinder turbo diesel. It claims its engine will outperform all the current Japanese bikes in its class in a 0-60 dragrace and has better roll-on through the midrange. Whether the project is viable or not remains to be seen, although the drawings, available at, are tantalizing.

But of all the diesel manufacturers, the Neander Motorcycle Company, also in Germany (are we seeing a trend here?), seems to be the most serious and is certainly the most advanced. Its bike uses an exceptionally sophisticated 1400cc, turbocharged, DOHC parallel-twin engine with dual counter-rotating crankshafts that pumps out 112 bhp at 4200 rpm, which certainly compares favorably with any of the bikes in its class. While contributor Alan Cathcart, who reviewed the bike last year, had issues with the engine's rhythm (which is obviously unlike that of the typical motorcycle) and the bike's heady price, he was impressed by its performance and handling.

The bottom line here is that while the diesel engine and motorcycles may not be a marriage made in heaven, there certainly seems to be a lot of heavy breathing going on. Although I wouldn't expect to see a showroom full of diesel bikes in the near future, my gut feeling is that sooner rather than later someone is going to build a commercially viable diesel-powered bike-most likely a heavy tourer or cruiser-and when they do, I'll be the first guy in line to try it.