Most of the generic off the shelf carb rebuild kits are sketchy at best. You get overhang into the internal galleries partially blocking them, overhang into the venturi throats slowing air flow and messing with fuel atomisation and add to that someone who grabs the wrong top gasket and installs it (some kits have 2 or even 3 different gasket configurations). I hand prep every gasket during assembly and it's a PITA but I rarely have issues with a carby that's choking on itself. Said it plenty of times, the Mikuni is not a carb for noobs. Some guys who've rebuilt Rochesters, Holleys and Hitachis pull fails on Mikunis...