Jeremy McWilliams had a bad weekend at Donington

Jeremy McWilliams retired after 15 laps of Sunday's British Grand Prix at Donington Park.

The Glengormley rider fell back to 18th after a promising start on the Proton KR three cylinder, two-stroke machine.

McWilliams opted to ride his old 500cc machine after encountering numerous problems with his four-stroke bike while his team-mate Nobuatsu Aoki finished 15th.

Valentino Rossi was first across the line but he was late demoted to third after being adjudged to have passed a rider during a yellow flag situation.

Max Biaggi was declared the winner ahead of Sete Gibernau with Rossi third and Loris Capirossi fourth.

The Ulsterman was disappointed with his weekend.

"I was on the two-stroke and it was just not backshifting very well," said McWilliams.

I wasn't going to risk getting injured racing for 18th place Jeremy McWilliams

"It was just one of those weekends where nothing went right for us.

"I had trouble finding the gears in the race so wondered what I was doing out there.

"The bike just felt like it was on the verge of seizing and I wasn't going to risk getting injured racing for 18th place," he told the BBC.

Meanwhile, John Donnan won the feature race at the Walderstown Road Races in Athlone on Sunday.

Donnan won the Grand Final ahead of Ryan Farquhar although the Dungannon rider did have the consolation of claiming victory in the 600cc race where he edged out Davy Morgan and Victor Gilmore.

Robert Dunlop claimed the 125cc victory ahead of Nigel Moore and Darran Lindsay.

Darren Burns took the 250cc class ahead of Farquhar and Morgan.

Meanwhile, Hilton Hincks, Marty Nutt, Richard Britton, Marshall Neill and Michael Swann will be among the main contenders at Monday's rounds of the Irish Superbike Championship at Nutts Corner.

The Nutts Corner meeting will feature two championship rounds in addition to the other usual classes.