Valentino Rossi is adamant Yamaha can improve its MotoGP engine performance for 2021, despite the current freeze on most areas of engine design.

To help limit costs in response to the Covid pandemic, MotoGP announced that the usual in-season ban on engine development would be extended.

It means most teams must use the same engine design from the start of the 2020 season until the end of the 2021 campaign.

The only exceptions are Aprilia and KTM, which both began last season eligible for the package of technical Concessions.

Aprilia will now be allowed to develop its engine as normal throughout 2021, while KTM - which lost Concessions during last year - can modify its design until the start of this season, partly to ensure it is ready to meet a reduction in engine changes.

But it is Yamaha that is under the most pressure in terms of its engine, suffering problems with a faulty batch of valves at the start of last season, which in turn revealed the factory had broken the homologation rules by having valves made by two different suppliers (and therefore not perfectly identical).

The eight engines fitted with valves from a different supplier to those in the sample M1 powerplant provided to technical control were parked by Yamaha for most of the season, limiting the scope of their eventual punishment (50 Constructors' points plus Teams' points at Jerez and Red Bull Ring).

But as a result, Yamaha riders spent most of the season rotating between just three of their five available engines, which had to be 'de-tuned' to meet the extended mileage, some of which topped 3,000km.

The good news was that the factory suffered no further failures after Jerez and, assuming enough of the valves present in the sample engine are still available, the full line-up of engine changes will be on hand for its riders in 2021, meaning maximum revs can return to their original levels.

That in itself will provide a performance boost, but with all four M1s already joint slowest through the speed trap during qualifying at the Jerez season-opener (tied on 284.9km/h), they are still likely to be weak on the straights.

As such, Rossi believes extra engine performance must be found by working in the areas not covered by the freeze.

"The engine is frozen but it's not an excuse," Rossi said. "I mean, in MotoGP now you can make a lot of things around the engine to improve the performance.

"From the electronic side, from the way to [cool] the engine to keep the engine with a lower temperature, and the [exhaust] pipes.

"So even if you cannot go inside the engine, you have a lot of different issues that you can improve. So for me if Yamaha work well and in the right direction we can do better."

In terms of his own areas of improvement, Rossi - switching to the satellite Petronas Yamaha team for his 22nd season in the premier-class - is targeting better qualifying.

"I have to work a lot on myself," said Rossi, who finished a career worst 15th in the world championship after missing two races due to the coronavirus. "We have to improve some areas like qualifying, which is so important now.

"Also we will push as always on Yamaha to try to make a good job during the winter to try to improve some areas. Because in the last years and also this year we were strong at the beginning of the season, but we struggled compared to our competitors in the second half because they are able to fix all the new things [on their bikes].

"With Yamaha, the end of the season is not easy. So next year will be a hard challenge and we need to arrive ready from the first race."

As well as the engine-related modifications listed by Rossi, MotoGP teams can continue to change the chassis - The Doctor taking another look at the carbon fibre swingarm in the closing rounds of last season - and also update the aerodynamics package once during 2021.

Yamaha plans to retain the same Factory-Spec (Maverick Vinales, Fabio Quartararo and Rossi) and A-Spec (title runner-up Franco Morbidelli) bike allocation, although the rules allow riders to chose between 'any engine or aero-body specification that the manufacturer homologated in 2020' for the opening round of 2021.