Reply To: Gv125s skipping second gear and vibrating more than usual
If the bike is older than 4,000 miles old, you could take a look at the clutch basket.
If you squeeze the lever in while idling , if it gets quieter = time for a clutch overhaul , sometimes could add to the gear slipping ?
Drain the oil and use Motul 7100 forever (it is possible the dealer used rubbish trade oil from a barrel in workshop, they don’t really play nice for gearboxes long term) – It just an idea.
Then go for a gentle ride , be slower , and see if gears shift through nicely.
Believe it or not, too much chain slack can mess up smooth gear changes and also remove the sprocket cover , see if the sprocket NUT (front engine) is loose or the washer is loose at all ?
If we can do these things first, come back and let us know if it helps.
Idling issue = Go to halfords and get “WYNNS XTREME FORMULA GOLD PETROL” (ignore redex, and ignore everyone else! They are trash)
Put half a tank of fuel inside and put 1/2 bottle of that formula inside that tank ===> Ride until it is 1 bar of fuel left. See if the idling improves (We are “soft cleaning” everything to do with fuel parts , so WYNNS will run through pump, injectors, fuel lines, then gets burnt away inside pistons and O2 sensors pick up last = This should possibly see if fuel clogging was an issue or not.
Idling at 1600-1800 all day is normal and it cannot be adjusted by you. It is ECU control to keep the engine idling
It would be a good idea to get fresh CR8E plugs and stay with them or get LASER ones (good plugs) = DO NOT use “Iridium IX” plugs as Hyosungs hate them.
IX = Blue Box (Avoid)
LASER = Rainbow box (CR8E LASER)
CR8E = Stock plug (yellow box)
Now as you finish riding until 1 bar of fuel left ===> Remove the plugs and show us the pictures here, so we can see if the threads have changed colour and how much. Also pictures of the “inside of the plugs” so we can see a trail of what’s going on (too much air, too much fuel, poor sparking (ie. failing coils or NGK caps which the ECU cannot sense) = The ECU will not tell if the coils are failing or the plug caps have issues , you will find out the hard way when the engine stops altogether or starts firing irregular or shaking (power loss when riding too as running on 1 cylinder etc)
Take your time, I said a lot, but i expect some kind of indepth report back from you so we know every step you took and if it is doing better or not.
If it is something stupid like a loose plug or dodgy clutch bearing or 1 snapped clutch plate (happens but rare) , you will tell us and likely someone else will read this thread to avoid ££££££s of labour at garages who don’t understand Hyosungs at all.