Engine shuts off

[Gimpy]

Hi guys;
I put a 13 hp greyhound/workhorse/lifan engine on an old Yazoo frame. Did the sandblasting/repainting/weld repair project a few years ago.
The engine has been a champ until this year when I left it in the rain. I drained/flushed the crankcase, fresh oil, gas, etc. Pulled the head to check the cylinder, etc. The cylinder walls looked good and it would hold WD-40 for a good while (hours) before leaking past the rings. Lapped the valves as long as I was in there. They are tight; WD-40 will not leak through at all.
Anyway, checked it out thoroughly and found no problems. Until....
I just finished cleaning the carb. It will fire off right away and run like a champ for about 60 seconds then stops as if you turned off the key. It still has fire, the float bowl is full (and if you pull the bowl drain plug, plenty of fuel flow). No water in the fuel. The strainer in the fuel tank is clean, the shut-off valve is working, the fuel line shows no evidence of dry rot, etc. (though the fact that the fuel bowl is still full when it shuts off negates any of that as an issue anyway.)
I disconnected the low oil shut-off switch because I read in some other forums that folks were having problems with that although that seemed to be limited to go-karts in hard turns.
No change. Let it sit for ten minutes or so and it will give you another 60 seconds of flawless performance.
When it shuts down I can immediately pull the plug wire and put in another plug, hold it to ground and it has good spark.
It is electric start by the way.
Sprinkling fuel in the intake makes no difference once it shuts down. Nor does begging, swearing, throwing things or yelling at the dog.
Valve clearance is set to .006 intake and.008 exhaust.
good compression, full of oil etc.
Help!! I have too many projects in line to spend all this time on this mower.

Thanks guys.

I cleaned the carb as a matter of course, it was spotless. The performance was unchanged, I was just hoping that I would find sludge or something. When I am finished using engine powered equipment I shut off the gas and let it run dry rather than letting gas stay in the fuel bowl and turn to sludge.
Not always, but I try to not forget...

and yes, it has fuel. (wouldn't be the first time I missed an empty fuel tank.)that

[Michael Eddie]

The fact that spraying fuel in the intake will not get it running, but I thought for sure that it would run after yelling at the dog! Leads me to think it is an electrical problem. Though you may have spark after you pull the plug and test it, it could be the intermittent, after the coil warms up, it stops working. I would look more into an ignitor/coil problem. Check for frayed or split wires along the harness as well.

Hi guys;
I put a 13 hp greyhound/workhorse/lifan engine on an old Yazoo frame. Did the sandblasting/repainting/weld repair project a few years ago.
The engine has been a champ until this year when I left it in the rain. I drained/flushed the crankcase, fresh oil, gas, etc. Pulled the head to check the cylinder, etc. The cylinder walls looked good and it would hold WD-40 for a good while (hours) before leaking past the rings. Lapped the valves as long as I was in there. They are tight; WD-40 will not leak through at all.
Anyway, checked it out thoroughly and found no problems. Until....
I just finished cleaning the carb. It will fire off right away and run like a champ for about 60 seconds then stops as if you turned off the key. It still has fire, the float bowl is full (and if you pull the bowl drain plug, plenty of fuel flow). No water in the fuel. The strainer in the fuel tank is clean, the shut-off valve is working, the fuel line shows no evidence of dry rot, etc. (though the fact that the fuel bowl is still full when it shuts off negates any of that as an issue anyway.)
I disconnected the low oil shut-off switch because I read in some other forums that folks were having problems with that although that seemed to be limited to go-karts in hard turns.
No change. Let it sit for ten minutes or so and it will give you another 60 seconds of flawless performance.
When it shuts down I can immediately pull the plug wire and put in another plug, hold it to ground and it has good spark.
It is electric start by the way.
Sprinkling fuel in the intake makes no difference once it shuts down. Nor does begging, swearing, throwing things or yelling at the dog.
Valve clearance is set to .006 intake and.008 exhaust.
good compression, full of oil etc.
Help!! I have too many projects in line to spend all this time on this mower.

Thanks guys.

I cleaned the carb as a matter of course, it was spotless. The performance was unchanged, I was just hoping that I would find sludge or something. When I am finished using engine powered equipment I shut off the gas and let it run dry rather than letting gas stay in the fuel bowl and turn to sludge.
Not always, but I try to not forget...

and yes, it has fuel. (wouldn't be the first time I missed an empty fuel tank.)that

[Gimpy]

Thanks. A friend commented that the electronic ignition module may be bad which fits in with your suggestion. I guess I will be pulling the flywheel next along with inspecting the wiring harness. Any quick test for the module other than replacing it?

[Gimpy]

Have too many chores to do today to pursue, but did find a (new) coil on E-Bay for ~$12.00 + $6.00 shipping. Seems as though most suppliers (like Jackssmallengines) want $45.00 and higher. Probably my best shot once I test the coil at ambient and higher temperatures for resistance or other changes.

Thanks so much for the input

Incidentally the problem I was having on my Cushman Commander with smoking and power loss, (fuel in the oil) was indeed the fuel pump as you guys suggested. I made a new diaphragm from an old inner tube and it has been running like a champ ever since. Interestingly enough, I noticed that my Massey-Ferguson engine was acting 'tight' after warming up. You guessed it; fuel in the oil. You also guessed it; bad diaphragm in the lift pump. It least I now have had experience; one more home made diaphragm and we're 'on the road again'...

You guys are great.

By the way, the dog has recovered.

[Gimpy]

Ok, so it had gas. What it didn't have was a good spark plug.