Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

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TN2620

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• Apr 16, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #1

Hi,

I have a riding tractor with a Briggs & Stratton 12.5 hp engine. When I start the mower it runs great for about 30-40 minutes, after which it begins to stutter and spews an incredible amount of white smoke. I cannot tell exactly where the smoke is coming from because it looks like the entire engine is smoking. Sometimes if I disengage the blade I can keep it from stalling out, but as soon as it's engaged again, it only traves about 10 yards before stuttering and smoking again until it finally stalls. Once it stalls I am able to restart it, but it continues to stutter and stall. I've changed the oil and ensured that I have not over-filled the crankcase. Thanks in advance.

TN-2620

 

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bertsmobile1

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #2

White smoke = oil burning.
Run the mower till it starts to smoke then remove the oil dipstick.
If you get smoke signals from it then head gasket has gone which is very common on Inteks.
Oil leaking from the rocker cover drippng onto the muffler will also make white smoke.

Unfortunately 12,4 Hp Briggs & Stratton is less than meaningless to those who would dearly like to help you.
What would be really nice is themodel number and code from the engine which will be either stamped into the cowel near the spark plug if the engine is as old as I am.
Or on a plate which is eother in the same place or on the top of the engine cowel.

 

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #3

Thanks Bertsmobile.
Model number 285707-0143-01

 

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #4

If head gasket is problem, is that something worth fixing or doest it mean engine is shot?
I am mechanically inclined, just never worked on small engine.

 

primerbulb120

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #5

It's certainly worth fixing, a new head gasket is cheap.

Aftermarket gasket for $6: ebay.com/itm/HEAD-GASKET-FOR-B-S-REPL-OEM-271866-271075-271866S-271707-STENS-465-025-/261974789411?hash=item3cfeea0d23:g:1DIAAOSwBLlVdyV4

Genuine OEM gasket for $8: ebay.com/itm/NEW-BRIGGS-HEAD-CYLINDER-271866S-OEM-/152037677168?hash=item236626d870:g:hPoAAOSwuAVWv9~A

 

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bertsmobile1

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #6

No small engines are not difficult to work on.
Use the search box and search for Briggs & Stratton manuals.
There have been numerous post telling members where they can get fee downloads of Briggs manuals.
Go to the USA Briggs & Stratton web site, navigate to get manuals ( customer support / manuals ).
Plug in those numbers and get the free parts breakdown.
The hardest part of doing your head will be cleaning the silicone off the rocker cover, replace it with a gasket.
The only trick is to make sure the engine is at TDC with both valves closed before you take the head off and don't move it till you replace the head.

 

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TN2620

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• Apr 17, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #7

Thanks primerbulb.
After further inspecting the engine I notice that oil is not only present on the spark plug, but the carburetor is also covered in oil. Oil leaks onto the floor directly under the engine, but I still cannot locate the source.

An Internet search seems to indicate piston rings may be the culprit, among other things.
Thanks.

TN2620

 

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bertsmobile1

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• Apr 18, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #8

What we forgot to mention
What is the level of the oil on the dipstick ?
If it is overfull then the carb has leaked and filled the sump with oil.
Unfortunately this usuall blows the head gasket in any case.

I did ask some question in the first post that you have not answered yet

 

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• Apr 18, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #9

Oil is way over full on dipstick.
And bert, the only question you asked in your first post was answered.

TN2620 said:

Thanks Bertsmobile.
Model number 285707-0143-01

Click to expand...

 

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bertsmobile1

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• Apr 18, 2016 / Briggs & Stratton 12.5 hp, runs for about 30-40 min, then begins to smoke

• #10

Sorry got confused a bit.
The float has not cut off the fuel which has flowed down the carb dribbled into the cylinder thence filled the crankcase.
Thus when the piston comes down and compresses the crankcase the oil spews out everywhere.
Start by puting an inline tap in the fuel line, by prefference between the fuel pump and fuel tank.
Next drain the oil, fill the engine with some cheap oil and dump it again.
Clean all of the oil & gunk out of the carb.
Pay attention to the float valve, which was the original criminal.
Try to start the engine.
There iis a 99% chance you will still have to do a head gasket as cylinders ful of fuel can not compress and blow the gasket.