Export thread

I have a Craftsman push mower with a Briggs engine. The engine use to be easy to start, always on the first try. Lately it hasn't been so easy and sometimes I can feel it pull back when I pull it. Then the other day when I was using it, it started smoking terribly. White smoke. After I stopped it I noticed motor oil leaking from the exhaust. Any ideas? The mower has not been tilted at any great angle.

Hello & WELCOME to LMF...

Check the OIL Level... It is very likely Over Full... Because (while the engine was NOT running), Gasoline has ran into the carb... then into the cylinder ... and then into the crankcase, over filling the oil and causing your problems.
You will need to drain all the oil, put in fresh and fix the needle seat leak in the float bowel, and or inssstall a fuel shut off (in the fuel line) to prevent this in the future... :smile:KennyV

I agree with Kenny, it sounds like your carburetor is letting too much fuel through and it is seeping into the crankcase which will cause an oil/fuel mixture to get into the combustion chamber and if it can't all be burnt (as it won't be able to at that rate) it'll go through the exhaust valve as liquid and then out the exhaust.

Get it fixed ASAP, as running a mower with fuel in the oil won't be doing the bearings or piston any good, and the oil/fuel coming out of the exhaust is a fire hazard.

Yes to all of the above.:thumbsup: That gas/oil mix is particularly nasty inside an engine.

Today I checked the oil and it was a little high. I don't know what real high would even look like on the dip stick I dont guess but it looked to be about 3/16 past the full mark. Thats what like 4- 5mm.
I drained the oil and put in some more. Then checked the air filter. No oil on it but was very dirty so I changed it. Then I pulled out it spark plug. It was covered with oil, so I changed it too.
I started it and it was still smoking like crazy, so I stopped it. I started it a few more times after that and it seemed like each time it was getting a little better, then the last time there was no noticeable amount. I think it just needs to burn up all the oil that is in there. Is there anything I could pour into the fuel system that would help it?

Cdy291 said:

Today I checked the oil and it was a little high. I don't know what real high would even look like on the dip stick I dont guess but it looked to be about 3/16 past the full mark. Thats what like 4- 5mm.
I drained the oil and put in some more. Then checked the air filter. No oil on it but was very dirty so I changed it. Then I pulled out it spark plug. It was covered with oil, so I changed it too.
I started it and it was still smoking like crazy, so I stopped it. I started it a few more times after that and it seemed like each time it was getting a little better, then the last time there was no noticeable amount. I think it just needs to burn up all the oil that is in there. Is there anything I could pour into the fuel system that would help it?

Click to expand...

You could try some of that fuel system cleaner additive you can buy for vehicles, but I'd suggest just running it on pure gasoline and let it naturally clean itself out.

Hopefully it will stop giving you problems now, but if it persists, just come back here and we'll help you! :thumbsup:

Cdy291 said:

Today I checked the oil and it was a little high. I don't know what real high would even look like on the dip stick I dont guess but it looked to be about 3/16 past the full mark. Thats what like 4- 5mm.
I drained the oil and put in some more. Then checked the air filter. No oil on it but was very dirty so I changed it. Then I pulled out it spark plug. It was covered with oil, so I changed it too.
I started it and it was still smoking like crazy, so I stopped it. I started it a few more times after that and it seemed like each time it was getting a little better, then the last time there was no noticeable amount. I think it just needs to burn up all the oil that is in there. Is there anything I could pour into the fuel system that would help it?

Click to expand...

Maybe a shot of Sea-Foam, per recommended mixing instructions, but otherwise, as you've discovered, it'll take some time to burn off the residue. Keep a close eye on your oil level, your carb may need some attention.

Given that it happened suddenly and the oil isn't too high, I'm thinking that the exhaust valve seal is the issue. Not an easy fix.

Mini Motors said:

Given that it happened suddenly and the oil isn't too high, I'm thinking that the exhaust valve seal is the issue. Not an easy fix.

Click to expand...

This is on a Briggs engine...
Is there any type of valve guide seal on a briggs???
I can't place seeing any... But?? :smile:KennyV

Prior to all this, was it using oil extensively? Had you added any just prior to this happening?
and he's right, exhaust seal......no fun...I'd rather unbolt the blade and engine and replace with a good on off a 25 dollar mower.....but that's me........

Mowerdawg said:

Prior to all this, was it using oil extensively? Had you added any just prior to this happening?
and he's right, exhaust seal......no fun...I'd rather unbolt the blade and engine and replace with a good on off a 25 dollar mower.....but that's me........

Click to expand...

Oh, and seafoam or lucas fuel injector cleaner has been the best fuel stabilizer and all around additive i've used.....

Briggs does use valve seals on some models. You need the model and type of the engine and can look up diagrams on partstree.com

I noticed this very thing when my flathead Briggs & Stratton engine was leaking oil from the muffler. Figured I was working on Chevy engines for so long might as well open up the lawnmower and give it an inspection. Pulled the cylinder head off, and immediately noticed that oil was leaking out of the exhaust valve when I turned the engine by hand. First thing I thought of was the exhaust valve seal might be bad. I removed the exhaust valve and immediately noticed that it didn't even have one, only the intake valve has a seal. So then I thought, hmm, maybe the valve guide is worn out, so I knocked out the old valve guide and reamed in a new valve guide, but when I installed the valve/spring and retainer back in oil was still leaking out of the exhaust valve when turned by hand...

Now, through all of this a great deal of oil was leaking out of the engine which of course needed to be replaced. I buttoned everything back up, stood the engine upright, then checked the dipstick to see how much oil was lost. In shock, the dipstick was still full, in fact, the oil was reading over the necessary requirement. Long story short, just as Kenny said in an earlier post, fuel was leaking into the crankcase, which would also explain why the fuel consumption was so great as I was only able to cut a limited amount of grass on just one tank. So, I drained the oil, replaced it with some fresh oil, and rebuilt the carburetor. Problem solved... :thumbsup:

I have an old MTD push mower with a Briggs 3.5 hp motor that I use at the camp. Hasn't been used in a couple months and noticed today the the could not pull the rope to start. when I turn the blade by hand it goes real hard and oil comes out of the exhaust. I noticed that the oil level is just over full. Any suggestions

WELCOME to LMF...
Drain the oil, it is mostly gasoline anyway...
Remove the spark plug, turn the engine over a few times to blow out the oil, clean up the plug...
Then you will likely need to clean up the carb and check the float & needle seat... that's where the fuel should be turned off when the bowl is full... they can seep past & over time flood into the carb and down into the crankcase with the oil..... causing your problem..
To prevent this from happening in the future.. install an inline fuel shut off valve between the tank & carb... something like this: BRIGGS/DEERE/TORO FUEL SHUTOFF VALVE #494768 / #AM107340 / #54-3150 ~~NEW~~ | eBay
You can find them everywhere... :smile:KennyV

And do not let the plug wire rest in front of the plug hole. Don't tell any one but I have done this and had to put out a fire

Sent from my iPhone using LMF