Reply To: Bike will start & idle on choke but won’t when moved to no choke – GT125R
If they are IX plugs , they won’t be good for it. You want either the basic CR8E or LASER platinum plugs (but beware of fake NGK plugs now , it’s so bad there is even a post about it on NGK’s own website.)
If in doubt, get basic CR8E from halfords.
After that, verify that both coils are actually sparking the same colour.
If not, go here below:
Rectifier – How to Test Stator , Battery , Regulator – GT125R Carby
Report back to this topic with readings of the stator, coils (without caps) and caps (on their own)
Ensure the airbox is fully secure, sometimes the front carb exposes some of its lip on the front airbox hole, so air leaks mean poor running, it is very very very picky when it comes to making sure the bike idles with a sealed air system.
Get carb cleaner , turn off choke, increase the idle ==> spray the engine rubber inlets. If the revs change for whatever reason, you may have cooked / caked up old o-rings, a fresh set would help restore its vacuum loss
Intake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
Whatever you do, make sure not to stress the rubber pipes as Hyosung isn’t making new ones anymore (they moved on to Gv125-S EFi now)
Double check the jet sizes and tell us ? eg. Front and Rear Pilots should be size 15 (forever) and rear mains should 87.5 & 90 as a baseline but can go up to 90 & 92.5 if you have an upgraded filter.
Like here:
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
if the bike has cone-filters , it will never run right until it gets its airbox. Hyosung made sure of it. everyone tried and failed, so airbox is a must. If the air filter is dirty, replace it as there is less air going in to the engine to mix the fuel properly , hence boggy running.
I may have said a lot , but take your time. 1 thing at a time. if you do a lot at once, you won’t know if its making progress or regressing (getting worse).
Wise but last war is crucially to check cylinder compression when it has warmed up but… let’s deal with that LAST.