Could be too much oil in the engine. Check the oil level. If this problem just occurred and the oil level is too high have you changed the oil lately? Fuel leaking into the engine while the tractor is just sitting can increase the oil level.

Could be a problem with the engine crankcase breather system.

if fuel tank is located above engine carb (gravity feed - no fuel pump) would certainly check for raw fuel in crankcase oil by pulling dipstick and smelling residual oil on dipstick for the presence of gasoline.
If you do smell fuel, change oil & oil filter right away. Install and use an inline fuel shutoff valve before running engine again. Crankcase oil diluted by raw fuel loses it's lubricating properties - engine can go bang and lock up for good.

Thanks to the 1st and second followup suggestions. But the oil level or fuel in the oil is not the problem. Oil level is always checked and full or a litle under. The oil is coming out the black tubing inside the air filter housing. any other suggestions?

Problem with the crankcase breather system or failing piston rings.

You can check the condition of the piston rings by doing a cylinder leakdown test.

You can remove the air cleaner, pull the tubing out and get to it, wipe it off, place you lips against it and alternately suck and blow. Sucking should be pretty much unrestricted, it should quickly switch over to restricted when blowing. It will leak some. IF it does not do this, the crankcase breather is not working properly. The breather from practically any B&S will work on it by switching the hose. Clearance between the fiber disc and its' seat. Do not press on this disc.

Walt Conner

The GT235 w/ the Kawasaki had a bulletin for this.Briggs, my guess is maybe a head gasket starting. It would be nice if it were the breather. Watch over items such as dipstick seals that may be leaking externally. Vangard I think tho. Model and spec?

Thanks guys, I checked the air breather today and it looked fine and blew and sucked through it. How would i tell if its the head gasket? And if it is how hard is it to replace? I think i will get a dipstick gasket tomorrow and replace, low cost and easy fix just to try. The engine is Briggs Model 350777 Type 1137-E1 Code 98080411 Doe anyone know the year by the code? My guess is 98. 18 Hp v twin.

Code is
YYMMDDzz
Your engine was built August 4, 1998

The 11 is Briggs code for the plant, assembly line, shift etc.

A couple ways to check for head gasket-
IF it's REAL Bad, one cylinder may run noticeably cooler.

Usually however, if you remove the valve covers, you'll see a "mist" blowing out toward the push rod side.
The head gasket is very narrow next to the push rod galley and is the most common place for failure.

Your engine is a Vanguard which is supposed to be their better engine.

Download the IPL from the Briggs site and it'll have an exploded view + your necessary part#'s.
You'll see the "narrow" area I'm talking about.