Brivio unsure of engine failure cause

Rossi was holding fourth when his engine seized on lap five. His retirement leaves him 85 points behind title rival Casey Stoner with just four rounds remaining.

"It's too early to say if it was a problem with the pneumatic valves or if it is a mechanical failure that could have happened also with a conventional system, because that's likely too," Brivio told Italia1 television.

"It could be a real coincidence the fact that the pneumatic-valves engine broke on its first use in a race. We don't know that yet, but we'll verify it.

"There were some problems of fuel consumption yesterday, which by reviewing the calculations and re-setting the electronics we thought we had solved this morning, so we were more confident from that point of view."

Brivio agreed with Rossi's assessment that Yamaha were right to risk using the engine in their current position.

"Both the fuel consumption problem and the fact we were using a new engine could look like taking a risk, but in this situation where we must try to take Valentino to a competitive level and to make him fight for victory, that is exactly the condition in which you can take a risk," he said.

"If we had been five points from Stoner with a package - bike, tyres, etc - that could fight on an equal footing then we would have certainly have taken fewer risks. This is the situation where you could take a risk, because risking is part of racing after all."

He said the team had been working to improve their straightline speed since Ducati proved to have a large power advantage in the early rounds.

"This new engine is the result of a reaction which sprung after a difficult start to the season. The study of different solutions started, and who has work experience inside a racing team knows you can follow different paths to solve a problem," Brivio said.

"You can't follow five or six different paths simultaneously because then you'd need perhaps double the budget and three times as many people available, so you take some decisions and you focus on some aspects.

"In this case it was the engine with pneumatic valves. We tried to take it to the track as soon as possible. This is a reaction that at the moment hasn't worked, but this is a way to react.

"Obviously we aren't happy about the current situation, we would like to see a quicker Yamaha, so everyone is working. I can see the engineers working hard and putting a lot of effort, but the results aren't there yet."