Ryuichi Kiyonari says he is 'very sorry' to his team, sponsors and fans for his performance in the 2011 MCE British Superbike Championship after concluding his title defence with another lacklustre round.

The Japanese rider won a third BSB title in 2010, but save for two wins at Oulton Park and Snetterton, he has been a shadow of his former self on the HM Plant Honda this year, with results fluctuating between the top five and well outside the points.

Though he scraped into the title showdown, Kiyonari scored just 18 points over the final seven races, finishing 17th, 16th and 11th at the Brands Hatch season finale.

Handing over his BSB crown to Tommy Hill, Kiyonari has apologised for his 2011 performance, adding that he doesn't know why his pace has been so inconsistent this year.

"It has been a too bad year for me - machine has been good, but not me and my personal problems," he said. "I do not know what is wrong, if I knew the problem then I could try to fix it. I am professional, always trying to improve, trying and thinking.

"Losing the championship title is a very big blow. That hurts me. It is very sad. I don't know why it is like this, I am very disappointed. Very sorry my team, very sorry to the sponsors, the fans, so sorry for everyone. I tried to put on a show and to do my best."