Yamaha suffered two embarrassing engine failures at Mugello with one of them costing their luminous superstar Valentino Rossi a chance of racing for a home race victory.

In the space of four hours at Sunday’s Italian Grand Prix the usually reliable YZR-M1 in-line, four cylinder engines came to a smoky end – one each in the bikes of Rossi and Jorge Lorenzo.

Yamaha’s red faces were eased when Lorenzo claimed a dramatic race win using a freshly installed motor in his M1 after a blow-up in the morning warm-up.

Rossi’s engine failure forced him out of the Italian GP on lap nine when he was second, just 0.135s behind Lorenzo in what was shaping as titanic all-Yamaha fight for victory.

“We don’t know yet what caused the problem, but we know what it is. It’s in the top end and something pretty irregular for us; the last time we can recall an engine failure in a race is Ben Spies at Indianapolis in 2012,” said Yamaha MotoGP boss Lin Jarvis.

“It’s extremely unusual to have two in a day. It’s something we need to look into in great detail.

“The materials will be sent back to Japan and analysed and for sure before the next race in Barcelona we will have the analysis and feedback, and we will have taken the relevant countermeasures.”

Under MotoGP rules Yamaha, Honda and Ducati are each allowed seven engines for the season which were sealed before the first race. Internal engine upgrades are not allowed.

The penalty for using eight or more engines include pit lane starts for riders.

“We have enough engines left in our allocation to manage the rest of the season comfortably, and we’re not worried about the quantity left,” Jarvis said.

“We’re more worried about losing points as we did at Mugello – losing the golden opportunity to come away with a one-two and only coming away with a victory (Lorenzo).

“Bad luck and good luck goes the same for that though, because we could have had two engines go in a race! Fortunately, Jorge’s was in the warm-up.

“It was a very unusual day, and we’re very sorry to Valentino that his potential race win wasn’t to be because of a mechanical failure.”

Both Lorenzo and Rossi have four fresh engines available for the remaining 12 races.