You'd better hope that, given what you describe, the fuel does NOT go into the cylinder. 2-strokes don't like liquid substances under the piston....
But, I take your question to mean your bike is peeing gas out one of the vent hoses when the gas is turned on?
Not an uncommon kdx issue, if it happening while it's on the side stand is what you're experiencing.
Maybe there is a bit of crud keeping the float needle from seating. A good chance your float level is off, too.
To check float level, remove the fuel bowl and make sure the mold lines on the floats are parallel to the body of the carb when the floats are raised just to the point the actuating tang on the float seats the needle. It presses against a sprung pin, so make sure you aren't depressing THAT spring during your check.
It's eaiser done with the carb off the bike. In that case, turn the carb upside down and lightly lift the float til it clears the pin, then very lightly let the float down until (again) the tang JUST touches the sprung metal pin that is integral to the float needle.
Adjustment to the setting is done by slightly bending the tab that presses against the pin. Don't bend the floats!
Be careful with the hinge pin of the float. Nothing is retaining it with the bowl off. It easily falls out. If you aren't careful, it might come out when you aren't looking....and it ain't running without it!
I run my floats a tad low (like 1mm) to ensure I don't have a peeing problem. I don't want to have to get off my bike in a hurry to give someone a hand and come back five minutes later to see a drip (or stream) that means I get to push my bike back to my rig.