Valentino Rossi took another small step down what he has warned could be a long road to restoring Yamaha to the top of MotoGP, during Monday's post-race test at Jerez.

While there were no major updates for factory M1 riders Rossi and Maverick Vinales, revised electronics were available to try and improve acceleration and rear grip.

"We didn't find something that changed our life, but some small details that we will use in the next races," said Rossi, who finished sixth in Sunday's Spanish Grand Prix, a decent damage limitation from 13th on the grid.

Team director Massimo Meregalli suggested the minor Monday tweaks were somewhat underwhelming.

"We have found some small improvements that can be used for the next GP in Le Mans. In all honesty, we expected something more significant but, in any case, another step was taken," he said.

"We will try new updates at the next test in Barcelona.”

Rossi was only 17th fastest (+1.677s) after 74 test laps, but the position didn’t mean much as he had shunned a time attack: "I didn't put a soft tyre. We concentrated on other stuff."

That included two new Michelin tyres.

"One was for Austria and Thailand. And it was good, because usually with that [stiffer] tyre, with the Yamaha, we suffer very much. The other tyre was also good."

As well as the long-running acceleration and grip issues, Rossi feels Yamaha needs better wheelie reduction through its wings, having spotted that Ducati and Honda were more effective in the race.

Vinales and Rossi have already homologated their two fairing designs for the season, but so far the Italian has opted to race the older version due to less drag.

"For me, now we suffer with the Yamaha for the wheelie, because our wings - like Quartararo also used in the race - are quite old and the downforce is not a lot.

"Also during the race I stayed with the Ducati and Honda and we suffered about the wheelie, so we have to do something.

"We tried the [newer] wings and they are not so bad, we can use in the next races. After that [at faster tracks] it’s difficult for the top speed, because already our top speed is not fantastic."

Rossi's subdued form at the Spanish Grand Prix, after back-to-back second places, underlined that while the weaknesses of previous seasons have been reduced, they are by no means eradicated.

While awaiting "all the small details, all the small steps" needed, Rossi reiterated his faith in Yamaha and knows that the bike can be strong at favourable tracks.

"The biggest difference compared to the last two years is that we work well and we go in the right direction," said Rossi, fourth in the world championship but only nine points from the Marc Marquez.

"The challenge is very difficult, the level of the top bikes is very high, so we need time. But we hope we can be more competitive in other tracks that are better suited to the M1."

Vinales set the fifth fastest lap time, 0.847s behind satellite Yamaha rider and test leader Fabio Quartararo, who set a record pace on a soft tyre.

The French Grand Prix at Le Mans takes place on May 17-19.