Starting fluid will dissolve the oil and any goo but will return to being goo as soon as the either evaporates because you are not removing any of the goo from the crankcase

If the lower end is full of fuel.   turn off the fuel, turn the ignition switch OFF and kick it over a few time to discharge the charged capacitor in the CDI box!!!.   Remove the spark plug, put it in 1st gear, hold the throttle wide open and push the bike until fuel vapor stop coming out of the spark plug hole.  The vapors will usually stop coming out of the spark plug hole after pushing it 30 to 50 feet.  This will clear out anything that will keep the engine from running. 


Air gap of .020" is fine if the crank is true, the bearing are tight and the bearing pockets are tight.  Some times if the gap is more than .040" it may not send a triggering pulse unless you kick the engine real rapidly.