The first day of testing after the winter break is always tough, and often deceptive. Riders spend the day trying to get their heads around mind-warping speed which simply can't be replicated by time on an MX or Supermoto bike. They have to deal with cramp in muscles they had forgotten existed, and which are only taxed by the very specific task of wrangling a 157kg MotoGP around Sepang's serpentine tarmac at speeds of over 320 km/h. They have to do all this in tropical heat, temperatures in the mid 30s °C and humidity of over 70% or more. The fresh-faced youngsters who spoke to us the day before are looking about 20 years older at their debriefs.

So sure, we have a timesheet, with names ranked in order of fastest lap. But that ranking should be regarded with a certain amount of caution. The first day of the test is a day of acclimatizing to riding the fastest racing motorcycles in the world again, and preparing for what is to come before the season starts. "The target today is just ride," Andrea Iannone said on Sunday night. "Ride, recover the feeling and arrive ready for tomorrow to start the plan we have."

Some recover that feeling faster than others, of course, and some aim to put in a fast lap and establish themselves, while others prefer to focus on getting back into a race rhythm, and working on all that entails. But in the end, the results should be taken with a grain or two of salt, at the very least.

You can't always trust the numbers

Sunday's results – it is confusing for a racing journalist to refer to "Sunday", and not have it mean the outcome of a race – are furthered colored by the fact that part of the grid threw in set of softs at the end of the day, and started chasing a fast lap time. The other part had either already stopped, or had their focus elsewhere.

So the final standings were very different from the order which had appeared with a little less than an hour to go. At the 45 minute mark, the top four were all veterans, four of the five oldest riders on the grid: Cal Crutchlow, Valentino Rossi, Dani Pedrosa, and Andrea Dovizioso. By 6:02pm, when the last rider was flagged off after his final lap, the top looked very different. Dani Pedrosa still led, having posted an impressive 1'59.427, and the factory Ducatis of Andrea Dovizioso Jorge Lorenzo were just behind him. But they were being harried by younger men such as Danilo Petrucci, Jack Miller, and Marc Márquez.

Maverick on the pace

Dig deeper into the times and it is a youngster who impresses most. Maverick Viñales spent all day working on race pace, and not worrying about his speed over a single lap. Yamaha need to ensure that the rear tire will still hold up after 20 laps, not drop off after 10, so Viñales put in a Stakhanovite total of 72 laps in conditions which ranged from very wet in the morning, to hot and dry in the afternoon.

His pace in those long runs was impressive, especially between 3pm and 4pm, the time when the race is normally run. In a run of roughly half race distance, Viñales strung together a sequence of seven laps in the 2'00s, and one lap in the very low 2'01s. He did six 2'00s in a row, more than any other rider managed all day. What's more, no one else managed to do more than a couple of 2'00s, nobody else managing to string such a quick set of laps together.

Yamaha had been working on a new engine and a new chassis. The new chassis was an evolution of the one used for the Valencia test, Valentino Rossi said. "The chassis of today is a new chassis, an evolution, but based on the 2016. So when I ride this chassis I feel better. My ride is normal. I feel better in the front and when I push I have good speed."

Yamaha also had two new engines to try, with better acceleration and a bit more top speed. That, too, was a positive for both Rossi and Viñales, though a common theme among all the factories with new engines was that they were a little hard to evaluate, as a new engine (even one with only minor changes) need to be remapped to extract maximum performance from it. Slightly different power delivery means different torque maps are required, and different engine braking settings, and much more. Yamaha, Honda, Ducati, all were wary of delivering an early verdict on their engines, preferring to speak instead of "potential".

The real work of Yamaha was focused on getting the rear tire to last. That was labeled a major success by both Valentino Rossi and Maverick Viñales. "I finished race distance with the tires, if not in [one long run]. And I have a good lap time after 20 laps," Rossi said. Viñales concurred. "There is a real improvement, because from lap zero to lap twenty, I just lost 0.3, 0.4, so that's very positive. I felt great with that, but still I think we can improve a lot."

Mr Confusion

That left the Movistar Yamaha garage feeling very positive, with both riders liking the feeling from the new chassis, the new engine showing promise, and tire wear probably not an issue. But it did leave us wondering about Johann Zarco. The Frenchman had two 2017 Yamaha M1s in his garage – the bike the Movistar Yamaha riders were desperate to get rid of at the end of last year. But Zarco was overwhelmingly positive about the bike.

"From that, I was working and I think we have a bike that is very constant," Zarco said of the 2017 M1. "We don’t feel too much the tire dropping." Zarco was consistently on the pace with Rossi and Viñales, though both he and Rossi could not quite match the pace of Viñales' long run. Zarco seems to be able to ride the bike the Movistar men struggled with last year, citing a different problem altogether. He couldn't put in the kind of fast lap he might need in qualifying, Zarco said. "The only thing that is weak at the moment is I am not fast enough. When I want to be fast and go in the 1'59s or low 2'00s, I’m not able to do it so that’s the work that we’re looking for."

Sorting motors

At Honda, they were focused on the new engine, and like Yamaha, the factory Repsol Honda riders had a choice of two to choose from. One was the engine Honda had brought to Valencia, and which both riders had immediately liked. The other was an evolution of that engine, a refinement of the development direction chosen with the Valencia motor.

Marc Márquez did not feel that there was an obvious winner, but he did feel that the newest version had the most potential. "We concentrate more on the last version, but also the second version has potential, but I think the feeling is like the last version has more potential in other circuits," he told us.

The most important thing was that Honda were already pretty much up to speed, and though there is still lots of work before the season begins, it didn't feel to either Márquez or Pedrosa that they were already stuck playing catch up."The thing is that we started, and we are at the same level as last year, more or less, but we have many new things to try and to adjust," Márquez said. "So this gives good motivation to a rider, and it's a good way to keep riding."

"It's important for the feeling to start in the right way and with a good base," the world champion said. "We started this time with a good base, we started to ride the bike and from the beginning, we were already on the same lap time as the other bike. So the engine was there, the electronics – of course we need to adjust the parameters, but the base was there. And this is important. I remember two years ago, it was completely out. It was losing power in the middle of the straight, in the corners it was doing something strange, but now it looks like they found a good to bring us something that is working from the beginning."

Changing chassis

The Ducati probably had the most visible changes, at least to an inexpert eye such as my own. All three GP18 riders – Andrea Dovizioso and Jorge Lorenzo in the factory team, and Danilo Petrucci in the Pramac squad – had one GP17 and one GP18 in their garages, and all were pleased with the new bike.

What has changed? The GP18 has a new chassis, a largish step which is only halfway to the new chassis design. The new chassis featured a raised swingarm pivot, and more material in the section below the pivot. The fuel tank has also been redesigned, with fuel moved down and forward, closer to the bike's center of mass.

The bike also had a new engine, though that was not immediately obvious from an external inspection. The engine was given a mixed reception, Danilo Petrucci already very happy with the motor, saying it was less aggressive and smoother, more fluid. "This means you can have more feeling and follow your instinct better, so this is good," he said.

Andrea Dovizioso was much more noncommittal. For Dovizioso, the improvement at the first touch of the throttle, which Ducati boss Gigi Dall'Igna had promised, wasn't immediately obvious. "I didn't really feel any difference," he said, "but they are still working on that." Jorge Lorenzo was evasive. Was it improved off the first touch of the throttle? "It depends on the corners," Lorenzo said. "But in some areas it's better."

Turning better, but not fixed

The factory riders were much more positive about the new chassis. "This bike looks much closer to my natural style," Lorenzo told us. "I can open the throttle quicker, I can enter the corner with more confidence, I can lean a little bit more, so I'm very happy, very satisfied." He was much happier overall with the results of the test, especially compared with last year. "I have a year of experience, and I understand more the bike. And the bike is more 'Lorenzo's bike'," he said.

Andrea Dovizioso echoed those sentiments. "I'm happy because already we found some better parts. Especially in the last part of the entry, the front is better, I'm able to enter a bit faster, and this is really good and I'm surprised about that." The new chassis didn't fix the turning problem the bike had altogether, but it was still a considerable step forward. "The good feeling I felt today is really good, I didn't expect it, so I'm really happy about that," Dovizioso said. "So the entry was better, the last part with braking and when I release the brake it affects the turning a little bit. So the difference is not in the turning point, but it affects also that turning point."

At Aprilia, they had a completely new bike – "95% new parts" an Aprilia spokesperson told us – which was an immediate improvement for Aleix Espargaro, and on which he set his best time. "The new bike lets me go into corners better and it reflects what I asked the Aprilia engineers for," he said.

KTM has a bucketload of parts, as you might expect, but the Austrian factory is moving more from revolution to evolution, from radical development to refining what they have. Pol Espargaro was happy, finishing the day in the top ten. "It's good to start where we left off in Valencia, which is the top ten," the Spaniard said. "I feel really good with the bike, and maybe the bike is not so different from the last bike in Valencia."

Testing continues on Monday, from which point the times should be taken a little more seriously. Riders are mostly back up to speed, and working on new parts, and engineers will have had an evening to evaluate and integrate the data found the previous day. Testing gets ever more serious from here on in.

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