The engines of the 500th Moto Cross World Championship

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technology & future

The engines of the 500th Moto Cross World Championship

The engines of the 500th Moto Cross World Championship
To each his own

Two-stroke versus four-stroke, David versus Goliath – almost anyone can win a race in the 500cc Moto Cross World Championship. Seven different technical concepts compete for success.

Lothar Kutschera


What the street Grand Prix scene is still hotly debating has long been a reality in the Moto Cross World Championship: an open 500cc class, in which it is lively two- and four-stroke and in which machines with the most varied of cubic capacities compete for victory. Only the number of cylinders there is absolutely nothing to shake, because more than one pot in cross-sport simply makes no sense.
The size of the single cylinder – two-stroke engines up to 500 and four-stroke engines up to 650 cm³ are allowed – varies considerably. Seven different concepts compete against each other. The two-stroke faction consists of Honda, Kawasaki and KTM. While KTM With a modest 368 cm³, the Japanese competitors use half a liter of displacement to the full. For the sake of completeness is still the 360 Yamaha should be mentioned, which, however, does not play a role in the World Cup.
For this, Yamaha has a hot iron in the fire with the four-stroke shooters, even though the engine measures only 426 cm³ and the competition comes up with significantly larger guns. Vertemati goes into the race with 503 cm³, the Husaberg single of the reigning world champion Joel Smets draws its strength from 595 cm³. Husqvarna is actually two-pronged. Some of the works drivers – including the current World Championship runner-up Yves Demaria – start with a 577 cc engine. The other part – including the German top crosser Bernd Eckenbach – is sent into battle with the largest, but also the heaviest single-cylinder: 633 cm³ and 32 kilograms of engine weight cannot be topped. When it comes to performance, too, Husqvarna is unmatched, as the factory safely stacks down with the officially stated 62 hp. Insiders assume that Eckenbach and Co actually have well over 70 little horses.
Naturally, every concept has its strengths and weaknesses, but the advantages and disadvantages outweigh each other in the individual sections of the route. So theoretically everyone can win, and the range of race winners is actually very large. The smallest two-stroke engine is just as much a part of this this year as the smallest four-stroke engine. Husaberg, Husqvarna and the new KTM four-stroke also achieved success.
Despite the balance of the field, two trends can be clearly seen. The dull rumble of the four-stroke engine is becoming more and more dominant – also because almost all top people have meanwhile said goodbye to the two-stroke engine. And within the four-stroke leger, Yamaha is currently the boss. Andrea Bartolini, top man in the Italian Rinaldi team, clearly leads the championship table after the sixth Grand Prix of the season with a 35 point lead.
The fact that the smallest four-stroke engine is currently making the biggest jumps can easily be explained. Bartolini’s driving class is just as well known as the fact that the 30-year-old, lightweight Italian works in an absolutely top team and gets a motorcycle that perfectly matches his driving style and stature: the Yamaha YZ 400 F impresses with its handiness, low weight and a very easy-revving, more than 57 hp engine. The engine, the only one in the field with a five-valve head and two overhead camshafts, can withstand up to 12,000 revs, which is significantly more than the competition. This enables Bartolini to circle faster through the corners and has a similar advantage as the V2 drivers over the V4 machines in the 500 road World Championships.
But he also has to accept the same handicap as his street colleagues: At the start, the large-volume competitors are usually first before him. “And in deep sand or mud,” adds Bartolini’s team principal Carlo Rinaldi, “we also have a hard time with the Yamaha. A little more displacement would help. “
The Rinaldi team uses Production Racers, which have been significantly optimized in all areas and trimmed for lightweight construction with the support of Yamaha Japan. In this way, the Italian team could achieve what the now disbanded factory team had not been able to do in the previous two years despite spending millions and hand-carved factory machines: the world championship.
Sure, the reigning champion has something against it. Joel Smets, tall and strong as a traditional 500cc driver, would probably not be able to cope with the lively Yamaha to be driven like a 250cc. The Belgian likes large-volume engines with a lot of steam from below – just like his Husaberg. But it also caused him some grief that year. The digital ignition of the new engine does not tolerate heat and has therefore stopped working several times. After three retirements in four races, it was enough for Smets. “Now we have installed the engine from last year again,” reported the world champion before the German Grand Prix in Teutschenthal in mid-June, where he promptly won a race.
A double victory would have been possible for Joel Smets. But Peter Johansson knew how to prevent this on the new four-stroke KTM in the first run. The Swede celebrated the second race win of the season in Teutschenthal, and thanks to another triumph for team-mate Shayne King in Italy, KTM can look forward to a successful premiere for the new engine. As with Yamaha, the Austrian single cylinder also hangs in a 250 frame, which ensures a low overall weight and good handling of the motorcycle.
In terms of engine size, KTM and Vertemati could definitely be trendsetters for the future. With just over 500 cm³ they have reached a level that should also be desirable for the competition. Yamaha will certainly add a little more displacement to eliminate the disadvantages mentioned. at Husaberg and Husqvarna can be expected to reduce the cylinder capacity in favor of better drivability.
In any event, it is desirable that technicians continue to have as much freedom as possible in order to maintain the appeal of this class. The plans of the world federation FIM, soon to only allow four-stroke engines up to 500 cm³ and to eliminate the two-stroke engines entirely, should better go to the wastebasket. Or are the federation strategists afraid that thanks to its technical diversity, the 500 World Championship will again become the premier class and overtake the 250 as the current top category?

The different models

Honda CR 500 R engine: single-cylinder two-stroke, membrane control bore x stroke: 89 x 79 mm displacement: 491 cm3 power: 65 HP at 6000 rpm gearbox: 5-speed engine weight: 29.5 kg? Dry motorcycle weight: 103 kg Husaberg 600 engine: single-cylinder four-stroke, an overhead, chain-driven camshaft, four valves, wet sump lubricationBore x stroke: 95 x 84 mmCapacity: XXX cm3Power: 65 HP at 7500 / minGearbox: 3-speedMotor weight: 28 kgMotorcycle dry weight: 109 kgHusqvarna 575/630Engine: single-cylinder four-stroke, one overhead, Chain-driven camshaft, four valves, wet sump lubricationBore x stroke: 98 x 76.5 mm / 98 x 84 mmCapacity: 575/630 cm3Power: maximum 62 HP at 8000 / minGearbox: 4-speedMotor weight: 32 kgMotorcycle dry weight: 113 kgKTM 380Single-cylinder two-stroke, Membrane controlBore x stroke: 78 x 77 mmCapacity: 368 cm3Power: 64 HP at 7200 / minGearbox: 5-speedMotor weight: XX kgMotorcycle dry weight: 98.5 kgKTM 520Motor: single-cylinder four-stroke, one overhead, chain-driven cam shaft, four valves, wet sump lubricationBore x stroke: 95 x 72 mmCapacity: 510 cm3Power: 56 HP at 7500 / minGearbox: 4-speedMotor weight: 28.5 kgMotorcycle dry weight: 105 kgVertemati 495Motor: single-cylinder four-stroke, one overhead, gear-driven camshaft, wet bore x stroke: 95 x 71 mm displacement: 503 cm3 power: 56 HP at 8300 rpm gearbox: 3-speed engine weight: 27.5 kg motorcycle dry weight: 116 kg? Yamaha YZ 400 F engine: single-cylinder four-stroke, two overhead, chain-driven? Camshafts, wet sump lubricationBore x stroke: 95 x 60.1 mm Displacement: 425 cm3 Power: over 57 HP at XXXX / min Gear: 5-speed engine weight: 29.5 kg Empty motorcycle weight: 105 kg ?

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