Marc Marquez spent much of the opening day at the Valencia test as the quickest non-Yamaha rider, despite a 'very strange' lunchtime fall that left a 2020 Honda prototypes in pieces.

Fortunately escaping unhurt, there was little Marquez could do but pick up some of the debris as he trudged through the gravel trap at the fast Turn 13.

"The bike was destroyed. When I saw some pieces, I just picked them up and put with the fuel tank!" Marquez said of his impromptu parts harvest.

"But yeah, it was a very strange crash, I was going out of the box, slow, but when I shifted up the gear, I just flew. It was with the prototype bike, but it was not any mechanical problem.

"Sometimes when you try new things you don’t expect that kind of reaction and it was a very strange crash. Lucky for us it was not a big issue on the body side and will not change the plan for tomorrow."

The reigning six-time MotoGP champion, who signed off the 2019 season with a twelfth victory at the same Valencia circuit on Sunday, said his main focus was to try a revised engine.

"Today we tried, not a complete 2020 bike, but some steps and those steps were some modifications in the engine," explained Marquez, who finished the day in fifth place, 0.535s from Fabio Quartararo (Yamaha).

"I just compared engines with the same chassis. Everything else was the same.

"Still the [new] engine character is more-or-less similar to this year and we are trying to work on different areas. But the first contact was not bad."

Marquez confirmed that he had tried a new frame during practice for the Valencia grand prix weekend "which he liked", but had gone back to the standard version for the race.

Wednesday's final day of testing will see the #93 try another frame as he and Cal Crutchlow share the load.

"We are the two riders that are testing new things," Marquez confirmed. "Me and Cal are working, not together, but in a different [areas] to understand more things for Honda because here in Valencia and Jerez are important tests because then they have all the winter time to keep improving."

Marc wasn't the only Marquez on track on Tuesday. Or indeed the only Marquez in the gravel, with younger brother and 2020 Repsol Honda team-mate Alex falling on the eighth lap of his full-time MotoGP debut.

"He started too early [this morning]," Marc said, referring to the cold conditions. "He was maybe the third or fourth rider on track and I said 'he doesn't know these Michelins!' And a MotoGP bike on a very cold track.

"Because when you don’t have experience, you feel like you can go out. Michelin is working very well because they bring very soft tyres but when it's very cold, it's very difficult.

"This morning was extremely cold and I already said, 'Turns 4 and 10 will be dangerous...' and he lost the front there. Unlucky for him. because when you get on the bike for the first time and crash you lose a lot of confidence and then he worked only with one bike all day.

"But then the progression was step-by-step, I don’t follow a lot because I was concentrating in my box, but Alberto [Puig] and Emilio [Alzamora] were trying to help him.

"But like everybody knows, MotoGP is difficult. Understanding the Honda is also difficult and, step-by-step, he needs to find his way to be faster and faster."

Alex, who was based in the LCR garage, returned to the track to complete 53 laps. He was 23rd and last but only 0.040s from HRC test rider Stefan Bradl, who also fell on Tuesday.

Might Alex be in the same Repsol pits as Marc for next week's Jerez test?

"I don’t know. This is something that Honda and HRC will decide. I'm just focussed on my pre-season because these are important tests, I have many items to do and at the moment I haven't even spoken with my brother yet today."

Alex later confirmed that he will be in the Repsol Honda pits at Jerez.

LCR's Cal Crutchlow was eleventh fastest on Tuesday.