Ryuichi Kiyonari admits it will be 'very difficult' to retain his MCE British Superbike Championship crown after a lacklustre weekend at Donington Park.

Having squeezed into the top six shootout, despite a run of inconsistent form, three-time BSB champion, Kiyonari had hoped to take advantage of the equalised points' system and start afresh.

However, the HM Plant Honda rider was off the pace in both races, retiring from the first due to mechanical difficulties before ending up sixth in race two.

As such, he is already 50 points off John Hopkins at the head of the standings, Kiyonari admitting he faces an uphill task to claw back the ground over the remaining five races.

"In the first race we had an engine problem which was disappointing for us. In the second race we had more problems. After five laps I had chatter at the front and we still do not know how to solve that. It is very difficult now to win the championship, but we will never give up."