Craftsman ride on lawn mower #917.270532

I have a 4 cyc 14hp brigg. & straton engin won't start.
Battery ok, i even jumped with my car
Solonoid ok, i jumped the terminals
Engine turns a partial rev. and stops
If i remove the spark plug, engine turns satisfactorily
I suspect the starter.
However, it seem that out of adjustement valves may be the problem?
What do you think? If valves, how differcult to adjust?