Briggs & Stratton 35 Classic engine, blue smoke + oil residue out of exhaust + Petrol in oil

[LochlanR]

Just bought and serviced a 35 Classic engine on a push mower, Started it and there was alot of blue smoke, although I did have to replace two back wheels so I had it on its side for about 20 mins. When i got it the oil looked to be over filled quite a bit so made sure to change it to the right amount before starting it. After starting, it took ages to burn off the oil until it eventually cleared. Used it to cut the grass and left it for a couple days. Just went to start it now and it shot out a cloud of blue smoke, its been kept upright and not on its side, checked the oil, its gone very dark gray after one use and smells a bit like petrol has mades its way into it.

What could be the issue? I assume it to be the piston rings or something relating to that.

 

[Rivets]

No, I’ll put money that the float needle is not sealing properly allowing petrol to run straight through the carb into the crankcase. Pull the dipstick and check if it is over full and smells like petrol. If it is time to replace the float needle and seat, plus change the oil.

 

[LochlanR]

The carb looks like this, how would i go about changing the float needle?

 

[Rivets]

Sorry, I guessed on the wrong carb, me bad. Two things now come to mind. One, is it possibly that you put 2-cycle petrol in the tank? Two, could you have over filled the oil?

 

[LochlanR]

Filled the oil to correct level, petrol is just normal E5 99 Octane from the pumps which ive used in all my B&G mowers

 

[Born2Mow]

This is a common issue when any fuel tank is mounted above the carburetor.

Gravity can/will force fuel to flow into the engine. (This may assisted by a tiny piece of trash stuck in the carb's float valve.) From there the fuel bypasses the piston rings and dilutes the engine oil in the sump. Such fuel systems are often fitted with manual or "automatic" fuel shut off valve. The problem is that when the automatic versions fail (go Open all the time), there is no way for the owner to tell... except that the dip stick will show an excess of fluid in the engine's sump.

► The carb's float bowl valve is not infallible. Even with the best of carbs, it is never a perfect seal.

► Running the engine with this diluted mixture can lead to extreme engine damage in a VERY short time.

You should 1) add a manual fuel ON/OFF valve between the carb and fuel tank, and then 2) start using it religiously.

 

[Scrubcadet10]

This is a common issue when any fuel tank is mounted above the carburetor.

Gravity can/will force fuel to flow into the engine. (This may assisted by a tiny piece of trash stuck in the carb's float valve.) From there the fuel bypasses the piston rings and dilutes the engine oil in the sump. Such fuel systems are often fitted with manual or "automatic" fuel shut off valve. The problem is that when the automatic versions fail (go Open all the time), there is no way for the owner to tell... except that the dip stick will show an excess of fluid in the engine's sump.

► The carb's float bowl valve is not infallible. Even with the best of carbs, it is never a perfect seal.

► Running the engine with this diluted mixture can lead to extreme engine damage in a VERY short time.

You should 1) add a manual fuel ON/OFF valve between the carb and fuel tank, and then 2) start using it religiously.

Where's he gonna put that?

 

[Born2Mow]

Where's he gonna put that?

Hopefully in the fuel line between the tank and carb.

 

[Rivets]

Born to Mow, do you realize that he has a tank mounted pulsajet carb. There is NO fuel line. Loch, the only way that this can happen twice is that you have oil which entered your tank somehow when you tipped the mower with the carb down. Run it a couple of times with fresh petrol and it should clear up. If it doesn’t post back and we’ll look for other solutions.

 

[LochlanR]

Hi, I tipped the mower before I serviced it, after I tipped it, I cleaned the carb, the fuel tank, new diaphragm, and new oil by extraction (not tilting the mower).

edit: also has had brand new air filter and filter housing cleaned