A crack in the head. or Bad rocker arms.
replace valve cover gaskets & spark plug tube seals
Spark plug wire not connected to spark plug? Spark plug wire connected to Wrong spark plug? Vacuum line disconnected? Bad spark plug or wire?
Your valve cover gasket is likely leaking, there are o-ring gasket around the spark plug holes that will cause oil to leak into the spark plug hole.
Wrong gap, wrong plug, poor groound when you are looking at the spark,
You may do serious damage to the lawnmower if the wrong spark plug is installed.
No there should not be any oil where you plug your spark plugs into
Could be that the threads are stripped on the plug or the head where the plug is screwed in. Or maybe it's the wrong plug..
Not definite, but possibly wrong timing when reinstalling cams and chain and heads, etc. other option is wrong spark plug wiring. spark plug wires on the wrong plug!
The wrong spark plug wire(s) can cause engine problems including not running but won't drain the battery.
To change the spark plugs in a Chevy Celebrity: 1. Give the spark plug boot a twist to free it up from the spark plug, then pull on the boot to remove the spark plug wire from the spark plug. 2. Use a 5/8" spark plug socket with an extension and ratchet or breaker bar to loosen then remove the spark plug. 3. Set the gap on the new plug to .045" then screw it back into the spark plug hole in the head. Tighten the spark plug and replace the spark plug wire. I change the spark plugs one at a time to keep from getting the spark plug wires on the wrong spark plug.
They are easy to find. Follow the spark plug wires down and pull of the spark plug boot. The plugs are right there.
somtimes usually not