Technology: Ducati's “Desmo” valve system
This week we got to see the Ducati crosser for the first time. The Desmo450 MX from Bologna will be used in the Italian Motocross Pro Prestige MX1 championship from March. The Ducati technology used is well known in motocross except for one item: The valve control in the cylinder head.
Modern four-stroke motocross bikes have conventional valve control with valve springs. The opening is forced by a cam that pushes the valve open at the right time. Closing is done by means of a valve spring that pushes the valve back against the seat.
A disadvantage of this system is that valves tend to float at high speeds, creating the risk of the valves hitting the piston and causing damage. This means that engine developers must take into account a maximum speed at which no damage occurs. It is one of the reasons why a dirt bike has a rev limiter.
Desmo
Ducati uses the name Desmo for the machines equipped with the “Desmodromic Valve System”. The brand is currently the only manufacturer that uses this method of valve control. In the past, Mercedes briefly applied it to their F1 racing cars of the 50s. Unlike a conventional system, the valves of the Ducati crosser are forcibly closed. It makes higher speeds possible with this system.
Benefits
Ducati has the Superquadro Mono on its shelves, recently launched as the most powerful single-cylinder in the world. This engine is also equipped with the valve system of Ducati engineer Fabio Taglioni. It is a brand new 659 cc short-stroke single-cylinder engine with desmodromic valve control. It inherits the racing character of the Superquadro and the desmodromic valve system that allows it to rev higher than any other engine and express itself in sensational acceleration.
It seems that this fact convinced the engineers in Bologna to also use the “Desmo system” on the motocross bike.
Every advantage has a disadvantage
The system has more parts and is more complicated. Because there are more moving parts (then with three camshafts, now with one), more mass has to be driven and that consumes a bit of power. At the time, shorter maintenance intervals applied to the system, but since its introduction in 1956, Ducati has continuously worked on the system, which has eliminated this disadvantage.
It seems that Ducati accepts the extra weight and associated small power loss, given that there is plenty of power available with a 450cc four-stroke engine. We currently have no idea, but there is a real chance that Ducati will also use the Desmo system on their 250F machines. They have proven in the past that they have the technology to also make light engines run like poison with this type of valve drive. By the way, it was a 125cc engine in 1956 that was first assigned this system.
The 125 GP Desmo turned an insane 13.000 revolutions per minute for that time. He made his debut in 1956, before Gianni Degli Antoni rode him to victory in the Swedish GP at Hedemora later that same year. In the following years, Ducati came close to the world title by winning three races, with Alberto Gandossi in Belgium and Sweden and with Bruno Spaggiari in Italy. In 1959, a young Mike Hailwood dominated the Ulster GP and finished the 125 World Championship in third place.
From 2025, the Ducati Desmo450 MX will be featured in the MXGP. By the way, nine-time world champion Antonio Cairoli and Alessandro Lupino will help with the further development of the machine. A few years ago, another Italian brand (Beta) took the step towards the MX. Last year Triumph announced the same and now Ducati also wants to claim a share of the pie. Motocross will gain three more manufacturers in just a few years. KTM, Suzuki, Honda, Yamaha, Kawasaki, GasGas, Husqvarna and TM have been warned.
Photos: Ducati Media House en Mercedes-Benz
Tekst: Danny Hermans
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