I've posted this same reply in another thread. However, for tyonek's sake, I'll do it again.
I think it's flooded. It happened to me so many, many times without me knowing the cause. It happened always when I let the bike tilt on its stand. The carburetor overflows and floods the engine. When I let the bike stand by the wall and is almost upright, it does not happen. What I did was I adjusted the float and it never happened again even if I let the bike stand on its own and the tilt is great. To make sure that it doesn't really happen again, I installed a new fuel switch and I switch off the fuel line when I let the bike stand.