Reply To: Bigger main jets upgrade size for gt125r 2015 Dec 16, 2019 at 10:47 PM #3602 ♠️ M77👑 Admin Topics: 40Replies: 2,986Country: UKBike Model: GT Moved to Technical. Yes you are correct for the 125 it is 90 front and 92.5 rear as an upgrade.👍 More about that here [Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250