Jorge Lorenzo's world championship hopes enjoyed a huge boost as he claimed victory at today's San Marino Grand Prix at Misano while nearest challenger Dani Pedrosa crashed out.

Yamaha rider Lorenzo enjoyed an unflustered run to the flag after the Repsol Honda of Pedrosa was involved in a collision with Hector Barbera on the opening lap.

Lorenzo now leads the way in the championship by 38 points from Pedrosa with five races remaining.

Pedrosa qualified fastest yesterday, but was unable to line up on pole after he suffered a locked wheel on the grid before the start, which had already been delayed by five minutes after Karel Abraham stalled his Ducati.

As the rest of the field streamed away for the formation lap Pedrosa was left behind, and although his problem was eventually fixed, he was forced to start from the back.

And Pedrosa's afternoon was over just a few corners later, the Pramac Ducati of Barbera clipping his rear wheel on entry to a left-hander and ending the race of both.

Barbera took full responsibility for the crash and apologised to his fellow Spaniard.

"I tried to slow the bike down, but I lost grip on the front," said Barbera.

"I'm very disappointed, even more so because I took out Dani in the process and that was the last thing that I wanted to happen.

"It was my fault that he crashed out and I apologise profusely to him for that."

Pedrosa's catalogue of woe cleared the way for Lorenzo to cruise to a commanding victory by five seconds from Ducati's Valentino Rossi, enjoying his best ever result for the Italian team at his home race.

Lorenzo admitted he would have had a much harder afternoon but for Pedrosa's misfortune.

"To be honest we have been really lucky today, because without the problem with the lights at the start Dani wouldn't crash," Lorenzo said.

"It was bad luck for him but an important win for us in championship."

Third place went to Gresini Honda's Alvaro Bautista by just 0.003 seconds from Tech 3 Yamaha's Andrea Dovizioso after the Spaniard got better drive out of the final turn.

Bautista's first ever podium came on the weekend that MotoGP remembered Marco Simoncelli at a circuit renamed in the Italian's honour following his death in an accident at Sepang at the end of last season.

Simoncelli had been due to ride Bautista's bike in the 2012 season.

"I am emotional for sure," said Bautista. "My first ever podium finish is very special. I am so happy. This is in memory of Marco.

"This is a very special weekend for me and the team because our memories of Marco are so strong coming here to the circuit named in his honour."

Ben Spies was fifth for Yamaha, ahead of Stefan Bradl (LCR Honda) and Nicky Hayden (Ducati).

MotoGP debutant Jonathan Rea came home eighth in his first race as replacement for the injured Casey Stoner at Honda, while fellow Briton Cal Crutchlow crashed out of fifth place on lap three.