New 2009 yamaha xt 250 idle changes at random. The dealer tried a different sized pilot jet and adjusted the mixture, but the problem is still there. And now I get 50 m.p.g. when 73 m.p.g. is advertised. The idle still randomly goes up and down when in neutral or while riding at steady throttle. They can´t figure it out.. Does any one know the fix for this problem?