Any reason a mikuni carb will puke fuel out of the breather vent and overflow tube besides sedementt in the bowl or blocking the needle?

 

Float issue?

 

Or float needle not shutting off properly? Do you turn the gas tap off when parked? If not try it and see if it changes. If it stops with the tap off the problem is in the carb. A further cause may be the accelerator pump leaking. May be time for a repair kit and strip down! How old is the carb?

 

I cleaned the seat and the needle and replaced my petcock so far so good.

 

if it does it again look with an eye magnifier and see if it has a polished ring around the rubber tip almost always around the center of the rubber tip float valve

if they do that twice and your riding it and its flooding turn the fuel off speed up and run it out of bowl fuel - then turn it back on you may have debris in the tank or the rubber hoses are being affected by the fuel we now have