Problem:  Leaking Briggs & Stratton Flo-Jet Carbs

Most likely cause of a dripping carb or gas in the oil is the inlet needle and seat. It could have a little dirt under it, particularly if it just started this. If it is original I would probably replace it, check the float to see that it doesn't have gas in it. If it does it is leaking and will not be buoyant enough to shut the fuel off. Many times all that needs to be done is to remove the float and needle and blow out the seat with air. If the needle shows a ring where it has been seating, replace it.

Another thing that can cause it is leaking of the nozzle behind the main jet. This is unlikely unless it has been removed recently. Pressure check the float valve before reinstalling the carb.  Another good move is to install one of the neat little plastic Briggs inline shutoffs.

The problem may be the nozzle above the main jet, if the main jet has been removed recently. There is a flange that looks like the face on an engine valve. This seals to the carb casting. If it leaks the gas runs from the float bowl into the intake of the carb. The float valve will keep letting it in as long as this lets it run out. There is a possible fix if this is the problem. Take an old nozzle and sand [NO BRASS OR ALUMINUM ON A GRINDING WHEEL, PLUGS THEM UP AND RUINS THEM] the threads off the nozzle then using some fine valve lapping compound or aggressive tooth paste, lap the seat using this modified nozzle. Next get a new nozzle and a Briggs kit part # 391413.  This kit is a tank repair kit for a 5 hp with the top of the tank warped so the gasket won't seal and it won't pump fuel.  It has some small Teflon washers that will slip over the nozzle and hopefully seal it. IF this is what is leaking, you have nothing to lose as you will need a new carb casting to fix it otherwise. Just be sure this is the problem first. If your float valve pressure tests OK This is a likely suspect.

Don't use a screwdriver to remove the nozzle unless you hollow grind the blade so the faces where it contacts the slots in the nozzle are parallel, Then grind the sides of the blade so it is the same diameter as the shaft, no flare out. Briggs makes a 4 way Jet wrench for this and they are relatively inexpensive. The taper on the screwdriver and the tend to spread the slots in the nozzle and cause it to bind in the threads and the blade must go to the outside edge of the slot. The taper on the average screwdriver gets in the threads and ruins the carb bowl assembly. Over the years I have probably had 25 carb bowls brought in with the threads jammed up and the nozzle stuck in them due to trying to remove the nozzle with a screwdriver. This is beyond fixing, new pieces only.

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