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Motor ran great, put it away after a cut.

Next time I tried to start it, it fired right up but then immediately died. I took the airbox off and tried again.

Again it fired right up but then started spitting a gas and oil mix out of the airbox and died.


What's going on here? I'm confused how this could occur especially after it ran fine before it was parked.

TheRealHenry said:

Motor ran great, put it away after a cut.

Next time I tried to start it, it fired right up but then immediately died. I took the airbox off and tried again.

Again it fired right up but then started spitting a gas and oil mix out of the airbox and died.


What's going on here? I'm confused how this could occur especially after it ran fine before it was parked.

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If its oil in the air filter then it sounds like your head gasket has blown between the cylinder and the valve chamber.
Supply the model, type and code of engine to check its that first.

Didn't check the oil level before starting did you? Float needle probably leaked filling the crankcase with gas

Walt Conner

Tinkerer200 said:

Didn't check the oil level before starting did you? Float needle probably leaked filling the crankcase with gas

Walt Conner

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I believe this is exactly what has happened. I worked on the mower a little more yesterday and found the oil is full of gas.

Do I need to rebuild the carb? I'm very unfamiliar with the 12.5. Mower was bought second hand.

Yes you will need to change the oil twice to gte rid of the gas
You will need to rectify the leaking carb by fixing the float needle.
how you do this will depend upon what motor & what carb you have.
Thus Plugs request for numbers.
You might also like to fit an in line fuel tap between the gas tank & the fuel pump or fuel filter depenfing upon the model.
Belts and braces approach but $ 5.00 says a lot of stuffing around.
Note you will still have to clean the carb or the engine will flood while you are driving but at least in future you will not need to do a double oil change.
When you get it running , check the dip stick tube and the crankcase breather in the air cleaner.
You might need to run it for 1/2 hour or so to clean the crud out.
If it blows a lot of oily fume into the air filter or smoke signals from the breather tube then the head gasket is gone.

As Berts said, yes it is a carb leaking problem but the fix may be simple.
These carbs on 12.5's i have come across that clean and replacing the float needle does not rectify the problem and i have resorted to adding a shutoff valve as a result.
If i were you, change the oil then take it for a spin and cut grass to see if it does indeed flood while running thus need rebuild\clean carb or else KIS and add a shutoff to prevent this again.
For myself,clean\replace never solved my problem so valve it is.

pugaltitude said:

If its oil in the air filter then it sounds like your head gasket has blown between the cylinder and the valve chamber.
Supply the model, type and code of engine to check its that first.

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Model: 28U707
Type: 1113-E2
Code: 030516Z0

Can someone explain what exactly the shutoff valve would do that will rectify the problem?

Fuel shut off valve or fuel tap will stop fuel flow when not in use.
The needle in the carb dont always seal which then
allows fuel to leak past and fill engine up with fuel where the oil is supposed to be.

pugaltitude said:

Fuel shut off valve or fuel tap will stop fuel flow when not in use.
The needle in the carb dont always seal which then
allows fuel to leak past and fill engine up with fuel where the oil is supposed to be.

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So simply by installing the valve and keeping it off when the mower is not in use, I can fix the problem?

I will not fix your current problem but it will prevent it hapening again.
You might be lucky and have not done any engine damage.
You won't know this till you have cleaned out your engine and tried it .

Changed oil, ran mower for 5 minutes. Changed oil again. Put a set of clamps on the fuel line.

We'll see what happens tomorrow when I go to crank it again.

When you run it check for signs of running rich.
8 stoking. blowing black smoke etc.
A lot of time it is just a bit of crud or water that holds the float open.
Tomorrow put some sort of a catch jar under the carb and slip off the float bowl and see what is in there.
Over time you get a build up of crud in the fuel tank which eventually finds it way into the carb.
One reason what the sprint motor is so reliable is it has that overflow type of fuel bowl and the tank is lower than the carb.

bertsmobile1 said:

When you run it check for signs of running rich.
8 stoking. blowing black smoke etc.
A lot of time it is just a bit of crud or water that holds the float open.
Tomorrow put some sort of a catch jar under the carb and slip off the float bowl and see what is in there.
Over time you get a build up of crud in the fuel tank which eventually finds it way into the carb.
One reason what the sprint motor is so reliable is it has that overflow type of fuel bowl and the tank is lower than the carb.

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I sure will.

I think I'll also change the fuel filter when I install the shutoff valve.

I'll change to ethanol free gas and start running some seafoam in it as well.

And put the shut off between the fuel tank and the filter ( I put them upstream of the fuel pump ) which will make changine the filter a lot earier in future.
Clamping off old fuel lines should be avoided if possible.
Ethanol should not affect the engine during the season when it is passing through the engine quickly.
Problems arise with it sitting long term.

bertsmobile1 said:

And put the shut off between the fuel tank and the filter ( I put them upstream of the fuel pump ) which will make changine the filter a lot earier in future.
Clamping off old fuel lines should be avoided if possible.
Ethanol should not affect the engine during the season when it is passing through the engine quickly.
Problems arise with it sitting long term.

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Good advice above.

Walt Conner

bertsmobile1 said:

And put the shut off between the fuel tank and the filter ( I put them upstream of the fuel pump ) which will make changine the filter a lot earier in future.
Clamping off old fuel lines should be avoided if possible.
Ethanol should not affect the engine during the season when it is passing through the engine quickly.
Problems arise with it sitting long term.

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I have my own theory of putting the shutoff valve after the fuel filter, so filtered gas goes through it instead of unfiltered gas which could crud up the valve over time. Is this a valid point, or is the amount of crud in the fuel not enough to hurt the valve over time? I agree that having the valve before the filter makes changing the filter a whole lot easier...

Pull one apart and have a good look how they work.
next to no chance of debris blocking a fuel ap and at $ 5.00, not a problem to rplace.
Only important thing to remember is to buy them from a mower shop, not of evilbay or craigs.
I can buy them for 5c from China howeve they are for water and will swell up and go to jelly if put in a fuel line.
Capitalist idiots with no consence flog these off endlessly on the web

bertsmobile1 said:

Pull one apart and have a good look how they work.
next to no chance of debris blocking a fuel ap and at $ 5.00, not a problem to rplace.
Only important thing to remember is to buy them from a mower shop, not of evilbay or craigs.
I can buy them for 5c from China howeve they are for water and will swell up and go to jelly if put in a fuel line.
Capitalist idiots with no consence flog these off endlessly on the web

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Thanks!

I am not an expert but I've been there, check your PCV valve. It may look like a rectangle apx. 2 x 4 cover with line going into it. If it sticks, your compression will blow oil out the carb and everywhere else it might be weak at. Just a suggestion. I have had it happen to me. Wash it good in gasoline or buy a new one for about $5.00 bucks. Good luck

MILITARIA said:

I am not an expert but I've been there, check your PCV valve. It may look like a rectangle apx. 2 x 4 cover with line going into it. If it sticks, your compression will blow oil out the carb and everywhere else it might be weak at. Just a suggestion. I have had it happen to me. Wash it good in gasoline or buy a new one for about $5.00 bucks. Good luck

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"Didn't check the oil level before starting did you? Float needle probably leaked filling the crankcase with gas"

"I believe this is exactly what has happened. I worked on the mower a little more yesterday and found the oil is full of gas."

??

Walt Conner