Ok " the pilot jet takes over from the choke , it feeds the first 1/4 of throttle, as venture gathers , its the needle jet / needle that feeds till w.o.t, . then its main jet, s so I suggest you remove the pilots , and really clean them , is it Mikuni, or Keihin carbs, Check all vacume hoses , are on , no air leaks,,, AND air box is fitted , this is a must,,,