94 zzr250. all of a sudden - won't start with fuel set to on, only when set to reserve. won't run without choke on to at least 3000rpm. (assuming this is what is making it run hotter than usual). idle mixture twisty thing down on the left isn't doing diddly squat. every 10 minutes or so throttle decides it doesn't want to happen, revs drop. you can catch them if you give throttle a rather violent flick and hope it holds above 10 grand. it's running like it has f*** all fuel, but it's got plenty. any ideas???