LCR Honda's Stefan Bradl joined Repsol Honda riders Dani Pedrosa and Marc Marquez, plus the Factory Yamaha team, for the start of a private MotoGP test at Austin on Tuesday.

Bradl - whose attendance looks to have been possible due to his new HRC Factory status - rode for 51 laps, setting a best time good enough for fourth on the timesheets, 1.434s from pace setter Marquez.

"It's a very nice circuit with an interesting layout and everything is well organised," said Bradl of the COTA facility, which made its F1 debut late last year and will hold its first MotoGP race in April.

"You can see it's a bit more for car races - especially in the first part - so it took me some time to find the ideal line but after some laps I started to enjoy it.

"After we have analysed the track, we started to work on the bike set-up because there are many hard-braking points and a lot of fast changing direction here. Overall it was a quite good first run out for us and I was positively impressed by this new circuit which is very technical."

Testing continues for the next two days.