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North UK

Are you able to get access / ride to a garage  (even a car one)   and tell them this….

1. Allow motorcycle to be least 20 minutes hot , from ice cold.
2. Remove both spark plugs   (just lift the tank for the rear nicely
3.  Put a compression tester in the front cylinder plug hole.
4.  Leave rear cylinder alone  (make sure it has no spark plug in it  (as per Korea’s instructions)

Press Start.
Hold bike on full throttle for 5 seconds.
See what the compression gauge says.

Then repeat the rear engine cylinder.

Come back to this forum and let us know the psi of each cylinder as it is crucial we get the engine out the way first.

===== If plugs are out, run to halfords and fit only the normal “CR8E”  and see if the bike behaves better ?

Don’t buy IX and don’t listen to the mechanics suggesting it.  Hyosung GT125’s don’t like “IX” plugs  (Blue Box) .   So i’d suggest only CR8E  (stock yellow box)  or  “LASER” type   (ones you see at this shop)

Also read this topic below, it has a lot of insight for you.     DEFINITELY MAKE SURE THE FLOAT HEIGHT is 7mm

GT125 2003 Performance Issues

Unsure?  Just replace the floats with new ones and get carb rebuild kits  (that contain new float seats and new needles)   = That will make sure the float assembly is working properly  (bad floats close early , bike starts to drop back speed rapidly and cuts off, because the jets don’t reach all the way to the bottom and carb is upside down too!)   (Sometimes O-Rings on the “gold float seats” can brittle away, and actually leak droplets of fuel through even after the floats have shut off the valves so to speak,  this called an internal leak,  too much fuel incarbs will bog it down too)

Mixtures = 2.5 turns out  (full circle) each pot and leave it alone forever  (yes forever) , if the bike has other issues,  still leave the mixtures alone forever 😉 ….way less stressful this way.

Let us know your progress,  excuse any grammatical errors in my replies, if i haven’t made sense,  just quote me to explain again in different way 🙂

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