Outdoor Power Equipment and Small Engines - Gas in oil pan

I have an old (1980) Craftmans rider mower with a Techumseh carb. The mower started running rough. After adjusting the carb screws, it helped a little, not totally but still used it. Went to start it another time and it looked like gas (maybe oil) coming out of the muffler. Then I saw gas in the oil pan. Ended up buying a new carb (broke old one taking it apart), cleaned oil filter (the foam type), changed oil, checked fuel ine for clog and put in a new plug. I asked Sears if the new carb came pre-adjusted and they said yes. So started it up with new carb and it still ran rough and I found gas in oil pan again. The only difference is no fluid spirting out of the muffler.

Any thought on what to check next? Thanks.

Not sure what you mean by the oil pan??? Post the model of either the engine or the rider to help diagnose.
Did you replace the entire carb including bowl and float, needle valve and seat? or just the carb body?

Mower model # is 502256124 Carb # I bought and replaced is 632183. By oil pan I mean the reserve that holds the oil - where the dip stick goes into. Also, the foam oil filter that was throughly cleaned, now smells of gas after the new carb was installed.

Ok well the only way I know of for fuel to get the air filter and engine oil is for the needle valve to not be working properly. It could be the float or the seat for the needle valve. Depending on any storage issues, it could be debris or build up from corrosion or stuck from similar.