Ok I know most cases is caused by running to rich... But my bike did good. Would 4 stroke for maybe mile them once warmed up would run perfect up to 40mph/8750rpm. Last week it started 4 stoking for a good 4-5miles before it would actually run right... Yesterday and today it won't stop at all... Top speed of about 25mph now. I don't know where to start. The main jet can't just all of a sudden be to big now... Or can it? Someone please give me some advise on what I should be checking please