The Spaniard dominated the second half of the first race, heading long time race leader Max Biaggi (Aprilia Alitalia) by 0.9 seconds. Despite slowing on the final lap, Marco Melandri (Yamaha World Superbike) took a clear third place.
Behind, Tom Sykes (Kawasaki Racing Team Superbike) took his best finish of the year in fourth, after a last corner move with fifth place rider Eugene Laverty (Yamaha World Superbike).
Checa repeated his efforts in the second race, to extend his championship lead over second place race finisher Biaggi.
The first running of the race was nullified when Melandri crashed and his machine lay in a dangerous position on the racetrack, leading to a 14-lap race, which determined all the places and full points.
Third place was fought over to the last possible moment, with Noriyuki Haga (Pata Aprilia) and Ayrton Badovini (BMW Motorrad Italia Superbike) third and fourth respectively. Melandri again crashed out, but Leon Haslam (BMW Motorrad Motorsport) kept it upright to take fifth.
In the championship, Checa has 245-points, Biaggi 173, Melandri 150, Laverty 123 and Haslam 106.