UPDATE: Yamaha loses Constructors' and Teams' points for 'failing to respect the protocol which requires them to obtain unanimous approval from MSMA for technical changes'

Yamaha's MotoGP title chances could be dealt a heavy blow following reports that the FIM is investigating the engines used during the Jerez season-opener.

According to La Gazzetta dello Sport, the alleged infringement is to do with the possible use of valves that do not exactly match those in the homologated engine design.

MotoGP rules stipulate that non-concession manufacturers cannot change their engine design after the start of the season.

The Covid delay meant that instead of Honda, Ducati, Yamaha and Suzuki providing their 'homologated' engine to technical control on Thursday at the Qatar GP, they were instead given a deadline of March 25 to send "a sample engine to the organisation, which must match those in the machines at the first 2020 event".

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Yamaha went on to suffer much-publicised engine problems at both Jerez rounds.

Maverick Vinales stopped with an engine issue in practice, then factory team-mate Valentino Rossi in the season-opening race. Both engines were subsequently withdrawn from use for the remainder of the season.

The following weekend saw Petronas Yamaha's Franco Morbidelli, using the A-spec M1, also suffer a failure in the race. That engine was also withdrawn.

Yamaha managing director Lin Jarvis later confirmed a request had been made to replace the valves but, when rivals asked for more information which Yamaha and its valve supplier declined to provide, the request was withdrawn.

"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," Jarvis said.

"[But] we were unable to provide the documents that were required and requested.

"At the same time, we discovered much more about the valve issues that we had. So finally we withdrew [the request].

"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."

In light of the apparent investigation, might Yamaha's decision to drop the valve-change request rather than provide documentation have made other teams suspicious?

Either way, Yamaha's management of the valve problem has certainly been successful in the sense that they have suffered no engine failures since Jerez. However, for reasons yet to explained, they've also clearly been avoiding using any of the Jerez 1 engines again, resulting in the rest of their powerplants facing high milage.

Surprisingly, the engines said to be under investigation by the FIM for potential non-compliance of the homologation rule are from Jerez 1, meaning they include the 'faulty' valves for Vinales and Rossi... Or perhaps the reason they were faulty was because something had been altered, knowingly or not.

The FIM is yet to officially comment - so it is not clear if it is only the Factory-spec bikes at risk, or also Morbidelli's A-spec machine - while the riders themselves were silent on the subject at Valencia on Thursday.

"That's a question for Yamaha and nothing from myself," said Quartararo, who won both Jerez races and starts the final three rounds 14 points beind MotoGP title leader Joan Mir.

"I know nothing about the engine situation," added team-mate Morbidelli, 25 points from the top after victory last time in Aragon.

Vinales also skipped the topic of the investigation but did reveal he's having to do fewer practice laps as he swaps between just two of his five engines.

The Spaniard's other three engines were all used during Jerez 1 and the only time any of those engines have been seen since is during practice and qualifying for Austria II.

But Red Bull Ring aside, Vinales has been using the same pair of engines from round two onwards.

"I'm on a really tight line! I'm running out of engines right now," said Vinales, second in the championship and 19 points from Mir.

"In Aragon I did just a few laps in the practices so I could not make many laps and could not set-up the bike in the second race, where the tarmac and the track was feeling very different. And we paid for it. We made a bad race.

"But anyway we are going to try to do it again in Valencia with less laps, trying to set-up the bike very fast. So I will spend a lot of time in the garage for sure, like in Aragon."

Morbidelli also spent some practice time in Austria with an engine from Jerez 1, but Quartararo has not completed a lap on either of his Jerez 1 engines since.

If an infringement is found and the Yamaha riders lose their Jerez 1 results, it would have a major impact on the championship standings.

Ducati's Andrea Dovizioso would take the win and move up to become Mir's nearest rival (-19 points), while Morbidelli would be the top Yamaha in fourth place (-36 points), behind Mir's Suzuki team-mate Alex Rins (-32 points). Quartararo and Vinales would both be 39 points behind, in fifth and sixth.

Since Vinales and Morbidelli then used the Jerez 1 engines again during the second Austrian round that race could also be in jeopardy, but Vinales crashed out with brake failure and Morbidelli took only a single point.