Gas in base?

[meanpolaris]

Hello, I just recently stripped down my engine. I cleaned out the base. I'm not a mechanic but am trying to do this myself. I'm putting a new top end in my RMK mod. After I left for a few hours, and came back, gas has filled my crankcase. How did it get there? and why didn't it happen as soon as I hauled my cylinders & pistons off? Any help would be greatly appreciated.

 

[99summitx]

I would say either the floats are sticking or a better bet is the needle and seat is sticking open and with pistons out there is no positive pressure at all in the crankcase allowing the fuel to flow. i had similar happen and was the needle and seat, looked clean to naked eye but replace and no prob since.