Engine spins but won't start

Hello. New to forum. Hoping to get some help.

John Deere
Model - D100
HP - 17.5
Year - 2011

Used mower several times this year already and ran fine. Filled tank several times through the spring with same fuel (though fuel was from tank that sat over winter). After cutting earlier this week for 25 minutes (8th cut of the year), engine went into a very low power and crawled across the yard until it shut down. Tried to restart but when I turned key, the engine would take about 3 seconds and do a slow (1/2 to one full) turn and then stop.

Fearing it may be bad fuel, I drained tank of all gas, added a new fuel filter, changed out the spark plug, added some new gas, and added a bit of fuel treatment. The air filter was fine. When I try to start it now, the engine spins very rapidly but never kicks over. Tried spraying starter fluid but no luck either. Any guidance will be greatly appreciated. Thanks.

In case anyone else experiences this, I'm posting the solution to the problem I posted. Turns out the push rod became unseated on the back side. There is a bolt behind both valves that secure the valves to a plate. The bolt on the Intake valve had worked its way out an 1/8 inch. I think this loosened the valve enough that the rod became unseated. I tightened the bolt, re-seated the push rod and tightened valves according to specs using a feeler gauge.

stwax said:

In case anyone else experiences this, I'm posting the solution to the problem I posted. Turns out the push rod became unseated on the back side. There is a bolt behind both valves that secure the valves to a plate. The bolt on the Intake valve had worked its way out an 1/8 inch. I think this loosened the valve enough that the rod became unseated. I tightened the bolt, re-seated the push rod and tightened valves according to specs using a feeler gauge.

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Good to hear.
Valves should be checked every 200 hours ( around 4 years ).
When ever the engine seems to turn over lumpy on the starter , suspect the valve lash.
Check that stud again at the end of the season, if it is loose again you may have over heated the alloy head so this will be an ongoing problem.
Use a gasket under the rocker cover, coat it with axel grease and it will strip clean making the job a lot faster.