Yamaha and star rider Valentino Rossi closed to within 21 points of the Casey Stoner and Ducati with victory in the recent Dutch TT at Assen, but the Italian still has two main areas of technical weakness compared with his young Australian rival.

Rossi's Michelin tyres haven't performed as well as Stoner's Bridgestones in the wet this season, while the 21-year-old's Ducati still holds the upper hand in terms of acceleration and top speed.

While Michelin works on its rain rubber, Yamaha hope to improve the M1's engine output through the incorporation of pneumatic, rather than spring operated, valves.

"They are working on [the engine] in Japan," Fiat Yamaha Team director Davide Brivio told La Gazzetta dello Sport. "It will arrive once it has been tested.

"We are lucky that in Japan they only have a one week vacation… I don't know if the new engine will be raced at Brno, but we should certainly have it to test on the Monday."

Pneumatic valve systems are already used by Suzuki and Kawasaki in MotoGP and offer advantages over traditional spring systems at ultra-high RPM. Ducati uses its own special desmodromic valve system, which manually opens and closes the valves.

The Czech Republic Grand Prix, the first event after the MotoGP summer break, will take place on August 17-19. Before Brno, MotoGP heads for Germany next weekend and the USA the weekend after.