Forums 🚥 PIT STOP 🔧 Hyosung Technical Help [Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250 Reply To: [Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250

  • Topics: 38
  • Replies: 511
Nov 30, 2017
North UK

Hi Guys I’m looking to upgrade my main jets and do a carb rebuild at the same time. My GV125 had been stood around for sometime before i bought it, in saying that i got lucky getting it going but i know it needs attention very soon. I’m looking for the correct jet size and a rebuild kit for the carb’s. As well as this I’m after some tutorial on how best to remove the carb’s as it was a nightmare the last time i done this and don’t want to struggle unnecessarily. Its fitted with straight through ss exhaust also, thanks in advance Shane

If your local dealer doesn’t have genuine Mikuni jets / EBC ones ,   you may send me a message as I for sure keep a stock of older genuine (on ebay) & some new jets.
I usually send jets with air filters on some custom orders.

I have dealt with the GV bikes a few times, one thing is for sure:
– Pilot Jets do not need upgrading at all.
– Stock main jets are identical  (87.5 front / 87.5 rear)

So a good upgrade commonly is the “90 Main Jet (Front)” and “92.5” (Rear)
Ofcourse the rear is bigger as its the hottest engine, so a bit extra fuel at the back has a cooling effect & slight torque boost in 5th gear.

If you head to Halfords or EuroCarParts – My fav cleaner for carbs is  WYNNS FUEL SYSTEM CLEANER – It’s a green can  , ofcourse any good carb cleaner will blast every hole clean.

Also , i must stress a little here – The “STARTER JET”  (which can’t be removed) has a very very tiny hole , ensure you have a good carb cleaner.

After the STARTER JET  (that big metal tube that you can’t remove) is cleaned up, your bike will start a LOT faster.

Starting / Cranking  = Starter JET
Slow Ride / Idle  = Pilot Jet/Main Jet
Normal / fast Riding = Main jet.

1 more thing.   Head over to poundland & get 3 cans of AIR DUSTER –  When the jets are dry , use the air duster to blow the holes clean.

Use the air duster to blow everything inside the carb, after it has dried up from a carb cleaner liquid.

A full clean will really do wonders to the bike. Good luck!

// Meditation doesn't mean you have to sit still....

Skip to toolbar