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GV125C 2012

I don’t want to sound like I’m being daft because i’m sure you’ve already done it but what I would do first is to confirm the correct functioning of the needle and seat.

I would get some clear fuel hose, connect it to the fuel inlet on the carb, fill it with fuel and watch it run into the carb (cableties for the hose on the handlebar to keep the hose above the carbs usually works). at some point it should stop. if it doesn’t that’s a dead giveaway that the needle, seat or float level is bad (because it should stop when the bowls are full enough). That should be part of a carb kit so I would be surprised if it wasn’t working correctly but good to confirm.

I haven’t rebuilt a carb (yet) but there should be someone more qualified than me to help guide you on here.

As for the hydrolock, there’s a possibility as well that the oil is contaminated with fuel, certain bikes have PCV systems and if the oil is full of fuel it could leak into the cylinder through the intake pcv system. (though i’m not sure about the hyosungs, but with anything like this, check everything)

Another possibility is a perished or damaged O-ring somewhere that is seeping fuel somewhere it doesn’t belong. I’m not all that familiar with the Mikuni carbs but it wouldn’t surprise me if theres an ancient o-ring that is now a black piece of goo and causing your leak.

I’m sorry i couldn’t be much more help but I thought i’d send this just in case it’s useful.