Honda has revealed that a broken radiator cap spilt hot water onto Dani Pedrosa's hands, forcing him to pull off and park his factory RCV at the end of Friday practice for the San Marino Grand Prix.

Pedrosa, who set the third fastest lap time behind Fiat Yamaha riders Valentino Rossi and Jorge Lorenzo, pulled off track on his final lap with vapour and debris emitting from his machine - in what looked like being a major engine failure.

But it seems the debris was from the broken radiator cap, while the vapour was caused by boiling hot fluid coming out of the top of the radiator. The Spaniard was seen shaking his hand vigorously as he stopped the bike.

"On my last run out we had a small problem with the radiator cap which broke and spilt some water on my hands, so I lost the final run and wasn't able to improve my lap time at the end of the session," said Pedrosa. "Still, this means we should be able to close the gap to the front tomorrow because my feeling from the machine was good today."

New rules restrict each rider to a maximum of five engine changes for the final seven rounds of this season. It is assumed that Pedrosa will not, as had looked likely, need to make an engine change.