Fuel overflowing out of carb

Hi everyone.

I built my first motorized bike a few weeks ago. I'm about 80 miles into the break in period. It ran great for the first 75 miles or so.

A few days ago, the engine started stuttering, then it died. I stopped and looked down at the engine and saw fuel gushing out of the carb - specifically out the back through the air filter. I don't have a fuel filter yet and I thought that a shard of metal from the fuel tank got stuck in the carb somewhere. I also checked the spark plug. It was black and oily.

I read Norman's carb disassembly thread. I took the carb apart, washed it and reassembled it. I'm pretty sure that the carb is clean and all the part move freely. I installed a new plug too. The motor runs fine for one or two minutes, then the carb overflows again. When I turn off the stopcock to the carb and give it a minute to dry, I can get another minute or two until - I assume - the float chamber empties.

Any ideas? Do I need a new carb?

I agree. I'm off to try it now.

Argh! I bent it down to about 45 degrees, reinstalled it, and turned on the fuel. It's still overflowing.

Maybe I still have some metal still up in the needle's seat? It's puzzling because the needle moves up and down very easily.

It's probably 80% full. No idea what fluid is inside it. I didn't think much of it because I assumed that it was watertight.

What should I do to it?

That's it. I'll order one today.

Thanks everybody! I'll keep you posted on the progress.