Fresh from his first MotoGP podium, Cal Crutchlow returned to the Brno circuit on Monday to set the fastest time during an official test.
All the Yamaha and Honda teams were present for the one-day outing, but Ducati has chosen to test at Misano on Tuesday and Wednesday instead, while some of the privateer CRTs were also absent.
Crutchlow led a Tech 3 Yamaha one-two by edging 0.117s ahead of team-mate Andrea Dovizioso
on the 43rd of his 47 test laps. Dovizioso only rode for 31 laps and was ahead when he called it a day at lunchtime.
Crutchlow's best lap time of 1m 56.461s was 0.187s behind the best of Sunday's race laps, set by Factory Yamaha world championship leader Jorge Lorenzo.
Lorenzo was third fastest at the test (+0.238s) having spent some of his 54 laps trying out an early version of the 2013 YZR-M1.
The Spaniard, beaten at the final turn by Dani Pedrosa
in Sunday's grand prix, set his best time on the 2012 machine and did not feel that the black-liveried prototype - which was fitted with the current engine - offered any improvements over his current package.
However Yamaha team manager Wilco Zeelenberg stated that there will be more upgrades to test next week in Aragon.
Repsol Honda rider Pedrosa, now just 13 points from Lorenzo in the championship, was the top non-Yamaha in fourth place at the test, a mere 0.004s from Lorenzo after 45 laps.
Much of the Monday attention was focused on Pedrosa's new team-mate, World Superbike star Jonathan Rea, who is set to stand-in for the injured Casey Stoner
at the next two rounds.
25-year-old Ulsterman Rea, whose previous MotoGP experience was limited to a private test on an 800cc Honda at Sepang in 2010, completed 61 laps of the Czech Republic circuit.