Yamaha has withdrawn its request to replace valves on its 2020 MotoGP engines, saying it was unable to provide the documents requested and now knows how to manage the situation for the remainder of the season.

The factory permanently withdrew three of its engines - one each for Maverick Vinales, Valentino Rossi and Franco Morbidelli - during the pair of season-opening events at a scorching hot Jerez.

All of the other engines used during the first Jerez weekend had also been temporarily parked and replaced by two new powerplants each for round two, meaning Vinales and Morbidelli have now opened all five engines from their allocation allowed for this season, with Rossi and championship leader Quartararo on four out of five.

While speculation initially centred around a faulty exhaust sensor, it has now been confirmed that it is an issue with the valves.

The design of MotoGP engines cannot be changed during the season, but it is possible to replace faulty parts – on the grounds of safety - if there is unanimous agreement from the other manufacturers.

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"One week ago we, Yamaha, made a request – not directly to the MSMA [manufacturers association], but to the MotoGP Technical Director, because that's the protocol if you want to open the engines in order to replace some part for a safety issue," Yamaha Racing managing director Lin Jarvis told the official MotoGP website.

"We made a request to replace some valves in the engines that we had stopped using since the two failures we had in the Grand Prix 1. We were then requested to provide more specific evidence, both from the manufacture of the valves and also the specific properties of the valves.

"During the one week since, we investigated deeply inside the factory and also we are in contact with our vendor and finally we were unable to provide the documents that were required and requested. And also at the same time, we discovered much more about the valve issues that we had.

"So finally we withdrew. It was a very short [second] meeting yesterday in that sense because we formally withdrew our request. What we will do to manage the situation is in the meantime we've been able to discover more deeply about the valves themselves, but also about the probable cause of the failures.

"So we will manage the situation. We are completely confident that we can manage without any safety issues on the track. We will do that by a combination of changing engine settings and also managing the rotation of engines throughout the season.

"The conclusion is; we have withdrawn our request, are confident going forward and will start to use some of those original engines from this weekend."

With Quartararo and Vinales first and third in the world championship, there had been speculation that Yamaha's rivals might drag their feet before agreeing to the replacement of parts, or at least want to see extensive evidence of the problem which could, in turn, reveal some secrets of the M1's engine.

Already one of the slowest bikes in a straight line, Valentino Rossi confirmed last weekend that the rev limit had been lowered 'a bit' in response to the Yamaha engine issues. However, Quartararo and Vinales claimed everything was 'the same as Jerez'.

Quartararo starts this weekend's fifth round with an 11 point lead over Ducati's Andrea Dovizioso. Vinales is 19 points behind in third, Rossi fifth (-29 points) and Morbidelli eighth (-36 points).