Defending World MotoGP Champion Valentino Rossi will ride a World Superbike-spec Yamaha R1 at a private test at the Misano Circuit in Italy this afternoon, the Italian set to test his fitness level to see when his comeback can begin.Rossi has made a quick recovery since breaking his leg on June 5 during practice for the Italian Grand Prix at Mugello and is opting to do the test today in order to better understand his current physical condition.”Riding a racing motorcycle will help Valentino and his doctors to plan the next stage of his rehabilitation programme in order that he may return to racing as soon as he feels confident to do so,” a press release from Yamaha stated.Rossi will ride an R1 provided by the Sterilgarda Yamaha team to the Fiat Yamaha team.