MotoGP: Ben Spies to leave Yamaha at end of the season

Former World Superbike champion Ben Spies says he will leave the factory Yamaha MotoGP team at the end of the season.

He said on Twitter: "I have chosen to leave Yamaha after this season for a litany of reasons. I will explain more when it is appropriate."

The tweets were later removed.

Spies, 28, has struggled this season and sits 10th in the standings without a podium finish, while team-mate Jorge Lorenzo leads the championship.

The American, who won the World Superbike championship in 2009, finished sixth in his debut season last year.

Spies had also tweeted: "I won't make any further comments until the official announcement comes out.

"I'm extremely happy to push for the rest of the season. To my fans, and myself, next year starts a new chapter. And yes I'm pumped."