For some reason, my 06 SDI is really fun to ride for about 45 minutes. After that, it loses about 500 RPM all the way through the range when you mash the throttle. This makes it really slow. Is the motor getting heat soaked and loses power? My clutches are cool so I know that is not the problem. It also doesn't hardly burn any oil. My friends SDI burns twice as much. Any ideas?