Ducati MotoGP rider Marc Marquez led the way in the post-Spanish Grand Prix premier-class Monday test at Jerez.
The grip level at the track was - unsurprisingly after three full days of action - described as being "super-super-super high, unbelievable", which was suboptimal for the purpose of evaluating new components (as was the reasonably high wind level).
Marquez sets the pace
Marquez shrugged off the disappointment of his crash from the Spanish GP to go fastest in both of the test's official sessions - before and after the midday break for practice starts.
His eventual benchmark of 1m35.876s - Marquez being the sole rider to dip into the 1m35s range on the day - was just under three tenths of a second off Fabio Quartararo's pole time from the weekend for Yamaha.
On a day KTM was known to have focused on aero work, its Spanish GP standout Maverick Vinales was second for Tech3 after pushing late on.
In doing so he moved ahead of the factory Yamaha duo of Quartararo and Alex Rins, who put a new engine through its paces and who both called it a day early.
Top 10 in the Monday test
1. Marc Marquez (Ducati)
2. Maverick Vinales (Tech3 KTM)
3. Fabio Quartararo (Yamaha)
4. Alex Rins (Yamaha)
5. Pedro Acosta (KTM)
6. Johann Zarco (LCR Honda)
7. Marco Bezzecchi (Aprilia)
8. Fermin Aldeguer (Gresini Ducati)
9. Raul Fernandez (Trackhouse Aprilia)
10. Fabio Di Giannantonio (VR46 Ducati)
The verdict on Yamaha's new engine
That engine is still an inline-four. Yamaha's in-development V4 is a way away from being ready to run in public - but the new inline-four spec brought here was deemed a success by Rins, who believes it offered an extra 2km/h of top speed.
Quartararo cautioned against reading too much into the peak figures, arguing that the level of grip and the track layout meant comparisons were deceptive - but his review was positive, too.
"That first touch was a bit too aggressive and then we adjusted the electronics to make it a little bit more smooth," he explained.
"The feeling was pretty good. We still need a little more time to really get the benefit of this engine but there are some positives."
It is notable if the engine does represent a step forward, as Yamaha has had an issue with peak power rather than usable power - having had to to cut back on top-end performance last year because the upgraded engines were making the bike too aggressive
What about Honda's new engine?
Yamaha and Honda are currently the only two manufacturers permitted in-season engine upgrades - as per 'Rank D' concession status - and Honda's newest version was in use during the weekend already, in the hands of wildcard rider Aleix Espargaro.
Espargaro - who stood down for the test, with fellow Honda tester Takaaki Nakagami riding instead - indicated during the weekend that the engine wasn't performing as expected, but here the verdict from Joan Mir was a more positive one.
Mir said it was "not a revolution but a small step in all the ways", specifically in granting more top-end power and making the power delivery more linear. But he also cautioned, like Quartararo did, that this wasn't the best track to evaluate top speed - and said Honda's current level was now strong enough to where it had to be "super sure" about any new components it introduces.
There was also a new swingarm - which Luca Marini hinted at being a small step forward.
Work at Aprilia
Aprilia ended the day in the top seven with Marco Bezzecchi, whose focus was aero work (with new seat aero in use during the weekend already) and work on a new carbon swingarm.
The component is aimed at improving stability, which Bezzecchi reiterated is "the area that we’re working on since the beginning of the year" - and which was also a focus for the work being carried out by tester Lorenzo Savadori.
In addition to Savadori and Nakagami, KTM had test rider Dani Pedrosa present and logging nearly 80 laps.
Michelin front tyre
An in-development new Michelin front was available here again - having been trialled already last year.
Spanish GP winner Alex Marquez said that the feedback was still generally positive - but that it wasn't as positive as in some of the previous tests, which he put down to Jerez being a more compact layout.
Marquez also acknowledged the big question was still whether the new tyre will see competition, given that Michelin will be replaced by Pirelli as MotoGP's tyre supplier in 2027. Michelin is "professional", Marquez stressed, but he acknowledged it may not make financial sense for the company to bring a new product that will be obsolete after a season.
The absentee
While LCR Honda's Somkiat Chantra ran for half the day despite his Sunday retirement due to arm pump, and Rins tested fairly extensively despite nursing several injuries from the weekend, VR46 Ducati rider Franco Morbidelli was kept out of action - his recovery for Le Mans from what the team is now describing as a cervical contusion an obvious priority over any extra mileage with a Ducati GP24 that won't change for the rest of the season.
VR46 team manager Pablo Nieto said "there shouldn't be any problem" for Morbidelli to race at Le Mans.
