Last fall I rode my 02 650 with no problems... this week I fired it up and it would only run good above 4000 rpms. With the enricher plungers engaged (choke) it runs but not smoothly. It is like it never gets warmed up. it is ridable, but at low throttle speeds it is unpredictable...it stumbles and then when it kicks in you better be holding on. Does it sound like a bad gas issue ( I do not think I used any stabil gas treatment in this bike last fall) or does it sound as if my jetting is messed up....I have had this back rejetted to match the custom open exhaust. Any help helps.