Sommer Diesel 516 516 cm³ (93,0 * 76,0), single cylinder, 20,5 : 1, ohv, rocker arms, direct injection, blower cooling, 27,5 Nm 2000/min, 8,5 kW (12 HP) 3500/min, 47 g/km, 4-speed, shifting right, single loop frame, steel pipe, closed joists, disk/drum, hydraulic, no ABS, telescopic fork, 2 rear spring struts, wire spokes, 3.25 - 19/3.50 H 19, 13,5 l, wheelbase 1,41 m, Seat height 760 mm, Payload 185 kg, kerb weight 165 kg, 105 km/h, 9.950 €, from 2017

It has been more decades than years since I once again discussed the advantages of a petrol engine in class. Turbos had not yet arrived in series production and would not have done so well either to the statement that with appropriate design one can speed such a gasoline engine wonderfully high. And my lecture ended with the conclusion that such an engine fits very well in principle to a motorcycle and I can't imagine ever finding a Diesel engine in such a vehicle.

A student came forward and said he had heard that there were such motorcycles in India. At that time, research was much more difficult than it is today, but ultimately led to the result that there was actually at least one Royal Enfield with a diesel engine. That was the day I decided never again to claim that there was anything not to be found in the field of automotive engineering. There would have been many combinations you can think of, e.g. SUVs as coupes or convertibles, but luckily I remained true to this premise and saved myself such embarrassments from now on.

If one were to equip such a vehicle with a 25 litre tank, a range of 1,000 km would be within the realm of possibility, as long as one could withstand it. No, such a machine is not suitable for long distances, much too slow. That's why you don't need such large tanks. It is much heavier than a motorcycle with a petrol engine of the same power. The consumption can but also below 2.5 litres/100km, which might be more difficult with a petrol engine.

Apart from the frame, the motorcycle is a Royal Enfield with a separate gearbox, into which a stationary small engine of the company Hatz from Ruhstorf in northern Bavaria is installed, which originates from the B-series. It is upgraded and converted a little for duty in a motorcycle. At the company of Jochen Sommer in Franconia, actually busy with the refinement of normal motorcycles, the whole thing is assembled. After all the origin of the engine owes the effort to the future owner to set it in motion by kick starter. It has an electric starter, but this doesn't change the somewhat rustic noise after the start.

We've chosen one of the smallest here. In the net such engines circulate with 50 kW and still much more, under it engines of cars like e.g. three-cylinder from the VW Lupo, more than twice as fast as our 516. These are almost all self-constructions, in the tip even with hydraulic all-wheel drive. We have discovered only one in a Honda chassis that is similar to the sound of a petrol engine. The rest, especially the single cylinders, encouraged to count the number of working cycles.

Once in motion, there may be, perhaps even the vibration behavior. It takes a little getting used to the behaviour of the former industrial engine. The cosy driving across the country road takes place almost exclusively in fourth gear, shifting down for an extra portion of acceleration seems rather pointless. In principle, a stationary engine is always optimized to operate close to its its nomonal speed. Another special feature is that Diesel engines usually require a longer running-in period than petrol engines. By the way, they also clearly reflect their treatment, can become uncomfortably loud or surprisingly quiet.

At low temperatures, however, they do not spread a sense of well-being. The electrical system can also be overwhelmed to start. Then the preheating is missing. By the way this testifies to how difficult it is to get a diesel engine running with a kick starter, even and probably especially if it only has only one cylinder. Decompression seems to be absolutely necessary here, which is either switched on manually as long as you kick, or left to an automatic which does so during the precisely calculated piston travel when kicking.

Also the exhaust detoxification is not exactly best possible. Since nobody seems to have heard anything about particle filters here before, the non-electric start in particular is clearly connected by a soot cloud. After all, our 516 avoids such a connection when accelerating. In general, the well-known Euro emission standards for motorcycles of this size apply only to a very limited extent, because parts 2 and 3 of these standards are not to be done with honest scarcely 100 km/h. So tested the 512 comes to Euro 4.

All that remains is to enjoy the 47 g/km CO₂ and to practice the way to the petrol station, as has long happened with owners of pure electric cars, in order to to say goodbye to the tenant of the the petrol station at some point.