The Bulgarian city of Pleven staged the third round in the FIM Supermoto S1 World Championship.
Wet weather made for difficult riding conditions in the first of three S1 races, each spanning 12 laps.
Mauno Hermunen of Finland was fastest at the start, with Briton Matthew Winstanley, the French championship leader Thomas Chareyre and his brother, Adrien, chasing hard.
But Hermunen held it together and took the victory from Italy's Ivan Lazzarini on his Honda.
Thomas Chareyre was third, with Slovenian Uros Nastran fourth and Winstanley claiming fifth.
Adrien Chareyre, meanwhile, dropped to a disappointing tenth.
He fared a lot better in race two, securing second place.
Again, though, Hermunen was the victor, completing his race in just under 17 minutes and 17 seconds.
Thomas Chareyre, Lazzarini, Nastran and Max Verderosa rounded out the top six.
The chequered flag in race three waved for Thomas Chareyre.
That was enough for second position in the Grand Prix of Bulgaria as Chareyre left Pleven with 65 points.
But it was Hermunen who won the GP after rounding off his day with a third-place finish.
For the second race in a row Adrien Chareyre was the runner-up, while Nastran was fourth just ahead of home rider Angel Karanyotov.
Thomas Chareyre now has 197 points in the championship standings, with Hermunen second on 175 and Lazzarini next on 171.
Round four will take place in Rijeka, Croatia.
SNTV