Tom Sykes has accepted fault for his bizarre failure to finish the second World Superbike Championship race at Portimao after crashing on the sighting lap on the run up to the grid.

The pole sitter had begun the day well by battling for victory in the opening race before fading behind Marco Melandri and Sylvain Guintoli on the way to third position, but his hopes of building on a run of eight consecutive podiums in race two was scuppered before he had even reached the grid.

Exiting the pit lane, Sykes explains he clipped the inside kerb of turn one, which was higher than he expected, causing him to flip over the front of the Kawasaki ZX-10R, hurt his leg and damage the bike.

Though he was able to get it back to the garage for swift repairs, Sykes - having started from the pit lane - managed just two exploratory laps before peeling back in again to effectively retire.

Going on to re-join the race and break the lap record whilst circulating seven laps down, a disappointed Sykes admits he feels he has 'let a few people down' with his costly mistake.

"I expected the first race to be just as close as it was, and obviously the guys who finished first and second were riding really strongly, but I was struggling a little bit with race performance. But we made a good podium and scored good points," he said.

"Portimao is not one of my strongest circuits and still we could fight for the win. In race two the fall was my fault because in turn one on my out lap I ran over the kerbstone on the inside. The piece of kerbstone looked quite flat but in the last moment I realised it was a big high kerb and it chucked me over the front of the bike.

"The bike flipped, landed on me and it was a big crash. It hurt my right leg and gave me a headache. We had made improvements on the bike for race two and we proved that was the case because we went on to break the lap record.

"I was just riding to the limits of the bike in each race. This is my worst circuit but in both races we raced to the limit of the package and it felt easier to do this record lap time in race two. I feel I have let a few people down but I do not want to be too hard on myself as it is the first mistake I have made for a long time."

Sykes remains second in the overall standings, but he is now 28 points adrift of Sylvain Guintoli.