Why is there Fuel getting in to my oil

I bought a sportser, and when I checked the oil it was very thin like water, and smelled like gasoline

So I did an oil change, and while trying to start it I looked down an there was oil every where,, the oil resavoir was overflowing from the cap and smelled badly of gasoline again, gas is getting in my oil some how ,has anyone ever had this problem and if so, can you please let Me know