Brno: Championship leader Marc Marquez topped the Czech Republic MotoGP free practice on Friday ahead of Sunday`s race, with the afternoon session disrupted by heavy rain that affected times.
The Spanish Honda rider and reigning world champion took 1min 56.803sec to cover the 5.4-kilometre (3.36-mile) circuit in dry conditions on Friday morning.
Fellow Spaniard Jorge Lorenzo on a Yamaha came second 0.037sec behind Marquez and 0.015sec ahead of Marquez`s Honda teammate Dani Pedrosa.
Italian Ducati rider Andrea Iannone dominated the afternoon session with a time five seconds slower than his morning performance, being one of only two riders who had their times measured before the downpour started.
Marquez set the best wet time ahead of Pedrosa and Italy`s Valentino Rossi on a Yamaha.
Forecasters predict more rain for Saturday`s practice and qualifying sessions.
At Brno, the 21-year-old Marquez is eyeing an 11th straight win in as many races this season, which would be a new record.
Italian legend Giacomo Agostini won the opening 10 races of the premier class season in 1968, 1969 and 1970, and Marquez equalled that feat at Indianapolis last Sunday.
At Indy, Marquez also became the first rider since Australian Mick Doohan in 1997 to win 10 races in a row.
However, no one has ever won the first 11 races of a season -- in part because Agostini`s perfect season in 1968 comprised only 10 events.
After 10 of 18 MotoGP races this year, Marquez leads the championship standings with a perfect 250 points, 89 ahead of fellow Catalan Pedrosa and 93 ahead of Rossi.