Carb flooding issue on ’02 Suzuki GS500 rebuilt carbs twice and still dumping fuel
I’ve been fighting a flooding issue on my ‘02 GS500 for about three months now and I’m completely stumped. The bike ran fine when I bought it last year but after sitting over winter it started flooding badly from both carbs. I pulled the carbs and did a complete rebuild with new OEM float needles, seats, jets, and gaskets. Put everything back together, synced the carbs, adjusted the float heights to spec at 24mm, and it ran okay for maybe two days then started flooding again. The left side carb was pouring fuel out of the overflow tubes.
So I pulled them again, checked everything, replaced the float needle and seat on the left side thinking maybe I got a defective part, and reinstalled. Same problem. Fuel just keeps dumping out.
I’ve checked the floats themselves and they’re not cracked or waterlogged. I’ve blown compressed air through all the passages. The petcock is functioning properly and not stuck open. I even tried setting the float height slightly higher at 25mm thinking maybe the spec was off but that made it worse. The weirdest part is sometimes it’ll start and run fine for 10-15 minutes then suddenly start flooding while it’s running. I’ll see fuel dripping from the overflow and then the engine starts running rich and eventually dies.
I checked the intake boots for cracks or leaks and they look fine. No air leaks that I can find. Fuel pressure from the tank seems normal when I test it with a clear line.
My buddy who used to work on bikes suggested maybe the float pivot pins are worn and causing the floats to hang up but they look fine to me and move freely. He also mentioned he saw someone discussing carb parts quality on alibaba and apparently there’s a lot of counterfeit OEM parts floating around which made me paranoid about whether I actually got genuine Suzuki parts.
Another friend rides a korean bike and said he had similar issues that turned out to be a kinked fuel line causing pressure spikes but I’ve checked my lines and they’re clear.
At this point I don’t know what else to check. Has anyone experienced flooding issues that persist even after multiple rebuilds? What am I missing here?