As other have mentioned, it sounds like a stuck (open) float needle. My concern is a possibly hydro-lock situation if it wouldn't turn over when trying to start it. Here's the theory: float needle is stuck open, fuel flows into the float bowl, but because the float needle is stuck open, fuel doesn't stop when the float bowl is full, so the fuel potentially flows through the intake into the cylinder, the cylinder fills with fuel. In your case, cylinder is full, then it starts flowing out of the vent tubes in the carb. I'd have to look closer as the design to see if it would flow out the vent tubes before flowing into the cylinder - I forget the heights and angles, so it's possible that no fuel flowed into the cylinder, but if it wouldn't turn over, that makes me think it did. You try to start it and it tries to compress the virtually compressible liquid fuel. Luckily, being a single-cylinder bike with probably an not overly-strong starter, it won't have damaged anything. On some other bikes (like a 4 cylinder Kawasaki Concours I owned), one cylinder gets hydrolocked, you hit the starter, and between a slightly stronger starter and one of the other cylinders firing, it 'really' tries to compress that liquid fuel and ends up bending a connecting rod. (I had a hydrolock situation, but luckily never damaged anything.)

I would suggest removing the spark plug and crank it over - keep away from any potential fuel that may spray out of the spark plug hole.

 

I'm going to crash this weekend.... Howl'in @ the Moon-Payson