July 18, 2005 Our recent articles on The coming of the electric motorcycle and the Electric superbike brought a flurry of response from our readers pointing out that the diesel motorcycle was a far more viable alternative to the petrol-engined motorcycle than the electric bike at this point in time. indeed, our readers were quick to point to a number of prototype diesel sports motorcycles that look awesomely promising: bikes such as the Neander 1400 turbodiesel, the TrackDiesel One Litre TurbuDiesel, the Dieselfighter, the AVL Boost and the Dutch ThunderStar 1200 TDI diesel motorcycle - all of them motorcycles of immense potential and all of them readying themselves for market. In this the first of a series of articles on diesel motorcycles, we take a close look at the ThunderStar 1200 TDI - a sports motorcycle with a stronger midrange than Triumph's 2.3 litre Rocket III.

Follow those links and you'll see a rich array of large capacity sports motorcycles in various stages of prototype readiness, but all offering incredibly low and mid-range torque - most of them boasting torque figures in excess of the motorcycle world's current heavyweight champ, the Triumph 2.3 litre Rocket III. Bearing in mind that the Rocket III boasts a maximum torque figure twice that of any other production motorcycle, and almost all of the aforementioned bikes have equal or more torque than the Triumph, it's easy to see why the diesel engine is seen as a logical match for a motorcycle. Highly respected consultancy company AVL's simulation tests suggest their deisel motorcycle would outperform a Suzuki GSX1400, Yamaha XJ1300, Kwaka ZRX1200R or Honda CB1300.

Which brings us to by far the most advanced diesel motorcycle on the planet at this point in time - The Star Twin ThunderStar 1200 TDI diesel motorcycle

The Star Twin ThunderStar 1200 diesel motorcycle was introduced to the public a fortnight ago at the MotoRai Motorcycle Show in the Rai (Amsterdam). It is an entirely different type of motorcycle to any diesel-engined motorcycle that has come before it.

Despite its name, the Star Twin ThunderStar 1200 TDI is a three cylinder diesel motorcycle but it has the performance and weight of a normal road bike.

Developed by Star Twin Motors in Loenen, The Netherlands, the project was initiated by the co-owner of Star Twin Motors, Kees van der Starre, who for years had looked at diesel motorcycles being fabricated with underwhelming results, knowing that new developments in automotive diesel engines could produce an engine that was as good, if not better suited for a motorcycle than a normal gasoline engine.

Van der Starre brought in Jeroen Bernart to create this motorcycle. He designed the motorcycle totally in 3D before starting to build it and by judicious use of lightweight parts and a frugal design, the THUNDER STAR 1200 TDI weighs just 205 kg, ready to ride.

“Almost everything you see with the naked eye is designed by us”, Star Twin’s Jeroen Bernart told Gizmag.

“We used different car and motorcycle parts internally. The car parts we made lighter, the motorcycle parts stronger.”

“And now for the number one question we are always asked”, he says smiling, “the diesel technology we used comes from a three cylinder diesel engine from the VW Lupo.”

“The bike uses a turbo charged, direct injection engine, with intercooler. It produces at the moment approximately 70 bhp and 160 Nm (118 ft pound) of torque. We will increase the power and torque later this year to more than 100 bhp and between 200 to 250 Nm of torque. We decided to slowly increase the power output of the machine, so we can easily see what the effects are and because it’s an enormous amount of torque on the drive train of the machine. It has five speed gearbox and a dry slipper clutch.”

Now 200 Nm of torque is indeed an outrageous amount of torque for a motorcycle to produce. If it produces more than 200, which seems likely, it will out-torque the fattest bottom-end in two-wheeled history – cos that’s what Triumph’s Rocket III produces.

The rest of the Star Twin ThunderStar 1200 diesel motorcycle is top class but conventional.

“A lot of the parts are made in Holland,” says Bernart.

“We used a Grand Prix front fork and a mono shock from White Power. Both very light and very good. The inner front fork tubes are made of aluminium for example.

“The front brakes are from the English PFM performance brakes, which gave us a suitable (and very light) brake disks and manufactured a new radial mounted brake caliper suitable for the front fork. The carbon wheels are from Blackstone Technology (BST).

How does the machine ride and what does it sounds like?

“Well, it drives like a normal super sport gasoline bike. The biggest difference, except for the sound, is the amount of torque you have at your disposal at almost every rpm. This results in that you do not notice in which gear you are, since it accelerates so hard in every gear.”

Why did you made a racer and not another model?

“Because racers and super sport motorcycles are the most challenging and difficult machines to develop. That is why we chose to develop a sports bike. It is easier to transform a sports bike into a touring machine or an all road model, than the other way around. And we have racing blood pumping through our veins.”

There are others who have or are constructing diesel engines in motorcycles, what makes this machine different?

“We are the first, at least to our knowledge, who have successfully made a diesel motorcycle which has the same level of performance and weight compared to gasoline versions. Other known diesel motorcycles have or too little power or have a weight above 300 kg.”

Will this model go into production?

“Probably not. This is a real prototype and is constructed like one, so it is not economical to make a large series of this machine in this state. For example, a very new casting method, called CAD/CAST has been used to make the prototypes crankcases.

“Perhaps we will manufacture a small series of machines like this ourselves, but the possibility also exists that the bike will be produced in cooperation with another company or companies."

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.

Technical specifications:

Engine: liquid-cooled 3-cylinder TDI diesel engine Cylinder capacity: 1200 cc Bore * stroke: 76.3 * 87 mm Compression ratio: 1:16 Injection: Direct injection Turbo / Intercooler yes / yes Transmission: 5 Frame: Star Twin racing frame Front suspension: WP GP front fork Rear suspension: WP GP monoshock Brakes front: dual PFM radial mounted 6 piston calipers and 320 mm discs Brakes rear: single Brembo 2 piston caliper with Star Twin wave disk Tires: front 120/70 R17 rear 190/50 R17 Rake: 23 degrees Wheelbase: 1533 mm Weight: 205 kg ready to ride Fuel capacity: 18 liters Fuel economy: 2.5 liters on 100 km

View gallery - 26 images