G4TR used a 19mm mikuni, vm, but made for the kaw...some differences on the intake side, to bolt to the rotary valve intake.
needle jet was 2.5
I would suspect first the pilot jet, but i dont have any info on what the stock pilot jet was. Sometimes, they are hard to clean, but it can be done. You can get the numbers off the jets, needles, etc and get them from sudco. so even if you have to piece together your own "rebuild kit", you could.