I was given a neglected zero turn mower that had been used regularly for the past several years. After charging the battery I started it up and let it idle for a few minutes before trying to move. I did notice that it seemed to be smoking a bit and once I increased the speed, the engine blows a lot of oil and white smoke out of the exhaust. It then quit running. I can get it to start with difficulty after this but it only runs for 5-6 seconds and then quits again. There seems to be fuel (and maybe some oil) leaking from the carb area.

Is this a major problem and should I look for another mower/engine?

Has fuel with oil accidentally been mixed and added to the mower? I only ask because I have a typical lawn mower and a 2 stage snow blower that I have pre mixed oil/gas mix for it set aside, well by accident my son added it to my lawn mower and it smoked like hell. Oil was coming out the muffler and white smoke was everywhere. I had to drain the tank and literally take everything apart and clean it. I flushed the carb, changed the oil and it still puffs a little white smoke on start up. So unless you are certain nobody mistakenly added oil mixed fuel I would drain and clean.
But the quitting thing mine did the same thing, it would idle and as soon as I would try to give it gas it would die, the spark plug was bad believe it or not it would idle for only a few seconds every time and then die. I had replaced the spark plug with the new advanced plug the year before so it was the last thing I suspected after tearing it apart, so I don't know if the oil mix somehow damaged the plug at the same time but it did. MY neighbor had the same problem with his snow blower would run for a few seconds and die. Told him get a new plug, he argued saying why would it run at all, I said I don't know mine did the same thing. 30 Min later it was running in his driveway... spark plug was the answer to that problem at least...
Otherwise you are getting blow by and the rings are worn and it letting oil get by the cylinder as the scraper ring is not cleaning the cylinder off and the excess is burning with combustion thus the white smoke. You could do a compression check on it when the engine is cold if you know the specs to give you an idea of how bad the cylinder is. A Wet oiled spark plug is also a indication of bad rings.
Good luck...
Bill

I really bet the "oil breather" needs to be replaced. Sign is the oil in the carb.

You'll notice a hose that goes nowhere from an assembly that screws into the block. This has a filter and a hose on it. Replace it from the outside.

Then concentrate on getting the oil out of where it doesn't belong. Use spray carb cleaner in the plug hole and with a rag over the hole crank the engine to get rid of the muck.

Do the standard other stuff.t

I inherited a Toro Zero Turn rider and it was blowing a lot of smoke, running poorly, and stalling. My local dealer told me it was a bad carberator. Had to guarantee I'ld pay for it, then send it in to Briggs and Stratton even though the Toro was less than 2 years old. Briggs finally agreed it was bad and replaced it. You can tell if you have this problem if your oil level grows higher than when you filled it indicating that gas is leaking into the oil chamber. My engine was a B&S 17HP. Still cost me the pickup and delivery charge even though the mower has a cover everything warranty. Everything but the engine. The engine was not included. We also had gas on the frame when we were running the mower. And gas under the mower when we stored it. At the time my dealer told me he had tried to repair many of these carberators without any success. They all needed to be replaced.

Now its running poorly again, this time the oil level is low and it might be that the breather hole is clogged?

Hope this helps. The zero turn riders are great at cutting grass.

Well I checked the breather assembly and it looked OK. Did see some oil in the breather tube where it enters the carb. Also cleaned the device on the gas intake to the carb where there is a hose going to the oil filler tube. Then the engine ran fine for about 2 min, then died as if it ran out of gas. Would not restart.

Next day I had gas all over. It was coming out of the carb everywhere all onto the garage floor. It was in the crank case over 1 inch above the dipstick fill mark. This was hard to see as the gas and oil did not mix together. Smelled like gas. Gas was in the air intake to the carb. I think the carb failed again even though the mower is less than five years old and the carb was replaced once. Probably explains why the gas tank was empty when I started this whitch hunt.

Other symptoms include the engine will not turn over completely even with a full battery charge. I assume its because there is too much fluid in the crank case.

Toro Zero Turn Riding Mower with Briggs & Stratton 18 HP OVP Engine.
Leaking gas. Blowing Smoke. Blowing Oil. Fire Hazard.

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Next day I had gas all over. It was coming out of the carb everywhere all onto the garage floor. It was in the crank case over 1 inch above the dipstick fill mark. This was hard to see as the gas and oil did not mix together. Smelled like gas

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Now its getting narrowed down. It either a stuck float or the needle seat is bad.

Sincee you found gas in the oil, change the oil. Get a carb kit and get a Needle Valve and Seat kit. (Kohler's, Honda's, and Kawasaki's will have the Needle Valve and Seat come in an entire Carburetor Kit [gaskets, o-rings, washers, etc]. Unfortunately, that is the only way you can get a Needle Valve and Seat.)

1. Temp plug gas flow to the carburetor. Remove fuel line. NOTE: **MAKE A NOTE OR DIAGRAM OF HOW THE GOVERNOR LINKAGE IS CONNECTED TO THE THROTTLE ON THE CARBURETOR.** Remove the carburetor.

2. Over a gas friendly pan 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. look at the new needle and seat valve. There will be grooves 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 recommend you take the carburetor 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.

Carb settings.

This is for float style carburetors only.

Screw in the adjustment screw until finger tight. Now back it out 1 1/2 turns. This should be sufficient enough for the engine to run properly. This adjustment if for all Briggs float style carburetors and all Tecumseh float style carburetors. If the engine does not run correctly, let engine warm up for about 5 minutes. Screw the screw in until the engine runs erratic (lean). Then back it out until the engine runs erratic again (rich). Now turn the screw half way between and this should be good enough

I'm on my third carburetor. Additives in the gas erode the coatings on the carb causing the bowl to overflow. Then gas works its way up the air intake onto the top of the engine block, through the breather hole into the crank case. You should see that your oil level is overfilled. With gas.

We've spilled gallons of gas onto the floor of the shed and the floor of our garage. Now we store the mower with the gas valve shut off so it can't overflow. We're blowing a lot of smoke but it still runs. We do have an issue with the electronic float control making poor contact and possibly getting wet with gas causing the needle valve to stay shut and the motor to stall. Wiggling that wire makes it run again for a while. We'll never buy a Toro mower or Briggs and Stratton engine again. EVER.