UPDATE 1-Motorcycling-Dominant Stoner takes second win in a week

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AMSTERDAM, June 28 (Reuters) - Australian MotoGP world champion Casey Stoner romped to his second win in a week at the Dutch Grand Prix on Saturday while Spain's Dani Pedrosa seized the overall lead from Valentino Rossi.

Ducati's Stoner, runaway winner at Donington Park in Britain last Sunday, was again in a race of his own at the Assen circuit as he powered from pole position to his third victory of the season.

Pedrosa was second on a Honda, 11.310 seconds behind, to leapfrog Rossi in the overall standings after the Italian fell on the opening lap.

After nine of the 18 races, Pedrosa has 171 points, Rossi 167 and Stoner 142.

"I really didn't want to make any mistakes today. I didn't want to have the weather in the mix, maybe throwing a few spits and spots here and there," the Australian told a news conference.

"But it managed to stay clear for the race so I'm pretty happy about that.

"As for Valentino crashing, it's very unfortunate. I don't want to catch up in points that way but I've had my run of bad luck as well from the beginning of the season. So it's time that we started to have some decent results."

Rossi, winner at Assen last year, fell and took out Frenchman Randy de Puniet's Honda on the first lap as the machine slid away from underneath him.