Kalex, winner of the last five Moto2 titles, joined its chassis rivals in making a debut with a 'race spec' version of next year's Triumph engine in testing at Aragon this week.

And the big news was that one of the riders aboard the Kalex was none other than Jonas Folger!

Folger - second as a rookie in last year's German MotoGP race - quit the Monster Yamaha Tech3 MotoGP team at the start of this season, due to the severe fatigue issues that had sidelined the young German since September's Aragon Grand Prix.

At Mugello, Folger's former boss Herve Poncharal said he was unable to contact Folger and ruled out considering him for the team's remaining 2019 KTM MotoGP seat, which was duly confirmed as going to Hafizh Syahrin.

"He has never been in contact with me, and also I don’t think he ever showed any desire [to return] - through any media or any friends," Poncharal explained, adding:

"If he [Folger] ever wants to come back here I'd be happy to talk to him..."

Things then appear to have moved quite quickly, with rumours at last weekend's Catalunya round suggesting some Moto2 teams (including Tech3) had now managed to contact Folger via his friends and that he was responding to text messages.

Intriguingly, there was also talk that Alpinestars had received a request for leathers to be made, (even though Folger previously raced with Ixon).

The reason soon became clear: Kalex had invited Folger to try its current and future Moto2 machines at this week's Aragon test.

It now remains to be seen if Folger feels fit enough to return to the class where he won three races during the 2014 and 2015 seasons.

"First a big thank you to Alex and Klaus [Hirsekorn], as well as to all employees in Kalex for giving me this opportunity and helping me lot during the last two days. The support from everyone was really great," Folger said.

"After the long absence from racing, it was a great liberation for me to return aboard a real race machine and it was also important for me to know how my current constitution is up to.

"I’m really grateful to Kalex for giving me this awesome opportunity, and for doing so, because everything was very spontaneous and easy too.

"Once back on the Kalex, I immediately felt comfortable with and I enjoyed riding a lot. Although, as said everything was very short-time, Alex and Klaus organized my ride perfectly.

"The first day with the old bike equipped with the Honda engine was good to settle in and get back the rhythm, it was an enormous help for me.

"But then, Thursday became even more interesting, riding the Triumph Kalex, however.

"Of course, I was curious about the differences in terms of engine characters and the new electronics used in this project.

"This package will definitely come a good deal closer to a real race engine. I was able to implement many experiences immediately and we made good progress throughout the day."

While Kalex had already been on track with a standard Triumph 765cc engine, as previously reported this week's test was the first chance to try an upgraded race version of the engine, plus the new Magneti-Marelli ECU.

Joining Folger on the Kalex were former grand prix rider Jesko Raffin and current Moto2 star Alex Marquez. No lap times were released.

"Things went very promising during our first test with the Triumph engine in race spec with the electronics coming from Magneti-Marelli for next year," said Kalex CEO Alexander Baumgärtel.

"Our riders for this test, Jesko Raffin, Alex Marquez and Jonas Folger, have done a great job over the duration of the last three days at Aragón.

"On Tuesday, Jesko started with the first rollout of this completely new engine package. Obviously, there appeared minor issues though that could be expected for what was the start of this still new project. But with the great support and efforts by the engineers of Magneti-Marelli, they could be solved immediately.

"Jesko did also still further functional tests. So, the first day as well as the second with Alex were completely dominated by electronic matters. It was necessary to provide as much information as possible to the three partners Magneti-Marelli, Triumph and ExternPro and we think, that we have completed this part successfully because of the abundant experiences of Jesko and Alex.

"In addition, we have been able to work out a different mapping with Alex during his last exit on Wednesday afternoon. This mapping with an improved rideability was a massive help for Jonas the day after."

"Jonas ride with the Triumph bike was then also very enlightening, as well as all three riders gave us very similar inputs and statements. This, of course, is very positive and useful to support Magneti-Marelli with further information regarding the fine-tuning in terms of engine brake, engine management and throttle control required for the Moto2 class.

"For the engine itself, there didn’t appear absolutely no problems whilst with the clutch, there is still some work to do for the race starts. This is probably due to the particular torque for this three-cylinder engine. Otherwise, the functionality is guaranteed, as well as the riders felt comfortable with the adapted power delivery.

"Apart from that, there came also praise for the gearbox which is working flawlessly so far though it is to say that this part as a whole was far from being stressed to the maximum. But also, from our side everything went smoothly with regard to the technology and mechanics parts.

"Therefore, we can continue working on the setup now and waiting for the next updates coming from Magneti-Marelli. In addition, we got positive comments from each of the three riders regarding the chassis handling.

"Of course, there is still a lot of work to do until the start of the 2019 season but we’re looking forward to this new challenge for us. But first, a huge thanks to Jesko, Alex and Jonas for their great job done and all efforts in these extreme conditions."

The official 2019 Triumph race engine is due to debut at November's Jerez test.

Meanwhile, Tech3 is yet to announce any riders for its new KTM Moto2 line-up...