2003 z1k, twice i have been on rides and the engine will pulse/stumble very quickly. It will cut power on and off so fast that the front end dives (kind of scary on the free way at 80mph) shortly after the bike will die. if i stop and cut the key switch off then on some times it will start up and run for a couple mile then the same thing. once i get home and let it sit overnite its fine then randomly starts doing it again. the fuel pump is new, everything else is OEM..........Whats going on???????????????????????????????????????????????