Gas in crankcase of rider

You could have a hairline crack somewhere,possibly the carburator, or a bad gasket seal.
You will need to change the oil.

The float valve is stuck open. Pull and clean the carb. Replace the needle and seat.
Drain the crankcase thoroughly, add oil to proper level. Remove the spark plug and drain the gas from the combustion chamber carefully. Make sure the spark plug wire is away from the gas .

Then clean the ENTIRE fuel system replacing the filter, and you may want to install an inline fuel shutoff.