GAS IS FOUND IN THE CRANKCASE OIL
When and if you find gas in the oil, change the oil and prepare to pull the carburetor off. Go to your local authorized small engine shop and get a Needle Valve and Seat kit. (Kohlers, Hondas, and Kawasakis will have the Needle Valve and Seat come in an entire Carburetor Kit [gaskets, o-rings, washers, etc]. Unfortunally, that is the only way you can get a Needle Valve and Seat.)
1. Stop the fuel flow to the carburetor. Remove fuel line. NOTE: **MAKE A NOTE OR DIAGRAM OF HOW THE GOVENOR LINKAGE IS CONNECTED TO THE THROTTLE ON THE CARBURETOR.** Remove the carburetor.
2. Over a pan suitable for containing gasoline, remove the fuel bowl nut and remove the fuel bowl.
3. Invert the carburetor and remove the float and needle valve by pulling out the float pin.
4. Remove the needle valve from the float.
5. Remove the needle seat by pulling it out with a piece of coat hanger wire or blow the seat out with compressed air from an air compressor. DANGER!: **IF YOU BLOW THE SEAT OUT WITH AN AIR HOSE, POINT THE BOTTOM OF THE CARBURETOR AWAY FROM YOURSELF, OTHER PEOPLE/PETS AND THE WALL.** Blow the seat out by blowing air through the fuel fitting. Keep blowing until you hear a pop.
6. Open the package the needle valve and seat came in and get the seat out. There will be gooves on one side of the seat. When you install the seat, spray some WD-40 on it and install the seat so the grooves face down in the carburetor, (you should see the smooth part of the seat facing you). Press the seat in with a flat punch until the seat bottoms out.
Remove the needle valve from the float and replace it with the new one in the kit. (Assemble the wire clip to the needle valve) On Tecumseh engines, the long end of the clip must face the Choke or air cleaner side of the carburetor. If you fail to do this, the needle valve will not seat. With Briggs and Stratton, Kohler, Kawasaki and Honda, it does not matter which way the end of the clip goes.
On Briggs engines 8-22 HP, the seat is brass and pressed into the carburetor. It can only be removed with a Tap and a bolt. I highly reccomend you take the carburetor in to a local shop and have them pull the seat out for you and reinstall the new needle valve and seat kit.
7. Assemble the float and needle valve to the carburetor. Check the float level. Make sure the float is parallel to the carburetor body. If you have a pressure tester, connected it to the fuel fitting. This will tell you if the seat will hold gas or not. If the seat can hold 5 PSI, then it is ok. Install the fuel bowl and nut.
Diaphram in the fuel pump going bad will direct the fuel from the pump into the vacumm line, into the head, and down into the crankcase. I just had a gallon of gas drain out of my crankcase. The carb has a solenoid shutoff that was functional. Wasted a lot of time chasing this; removing the carb, cleaning and testing. Fuel pump, easily accesible, right on the side of the engine.
What to do if someone changed the oil instead of them putting the oil in they end up putting gas in it