Yamaha engineers say that a software malfunction caused Lorenzo and Rossi’s engines to overrev and be destroyed. The team says that there were no changes made in the usual setup, and the entire blame lies with the spec software that didn’t behave as expected.
Valentino‘s failure was caused by an accidental over rev in acceleration that occurred jumping over a crest with full throttle at the end of the straight. This failure was not in any way related to the mistake made by Valentino at the San Donato corner on the lap before. There were no special mapping settings used for Mugello; we used the same precise mapping as always. We have now withdrawn both engines from the allocation for the season. We have learnt from this incident and already modified the rev limiter setting, so it will be OK in Catalunya. As a precautionary measure, the other engines used by both Valentino and Jorge in Mugello will be used only for practice sessions, until their life cycles are completed…We have already devised a countermeasure, so we are confident that the failures in Mugello will not recur.