Ducati Marlboro's Valentino Rossi testing the Desmosedici GP12 (Photo: Ducati Corse)

The only aspect of the Ducati GP12 that makes it ineligible for the current class is the displacement. If the engine is over 800cc, it is not eligible for the current MotoGP class.

Let’s try and keep this simple. The key difference between the structure of the GP11 and the GP 12 is that the rear suspension of the GP12 is attached differently to the engine. In order to adapt the suspension of the GP12, much preferred by Rossi, to the GP11, the engine needed to be modified so that, externally, it had the same mounting points for the rear suspension as the GP12. With the Ducati the engine is a major, stressed component and part of what we refer to as 'the chassis,' so adapting the 800cc crankcases to accept the GP12 rear suspension is not just a matter of welding on some new lugs and bracket plates. Rossi’s bike now has a new inverted swingarm that has been tested on Ducati’s new 2012 1000cc GP12 machine.

MotoGP Technical Director Mike Webb has explained that FIM observers have attended the GP12 tests and have measured the engines used and found no rules violation.

According to the Technical Director and to Ducati, all team testing prior to the Dutch TT of the GP11.1 (the modified 800 engines fitted to a bike with the rear suspension of the GP12) was done by the official Ducati testers, Vittoriano Guareschi (who doubles as team manager) and Franco Battaini.

So when Rossi leaves his garage today on the GP11.1, he will be riding the bike for the very first time, trusting his own impressions from riding the GP12 with the larger engine, trusting the theories of Ducati Chief Engineer Filipo Preziosi, and relying on the testing impressions of Guareschi and Battaini. If Ducati have been able to duplicate the rigidity of the GP12 engine in this modified version of the GP11, then Rossi will be riding a package virtually identical to the previous GP12 in everything but displacement and performance. This would be a step into the dark if it were the other way around -- riding a known package but with a bigger and more powerful engine.