less than 12 mo old lawn tractor with 17.5 HP briggs/stratton engine. good battery and brand new briggs/stratton starter motor (original starter broke). engine will not turn over if on compression stroke. starts fine if not on compression stroke. tried hooking a second battery up directly to starter and ground - same result. why can't starter overcome engine compression?

Phil, September 2013

Check the valve clearances. If the inlet valve has too much clearance, the compression release won't operate, giving the symptoms you describe.

Phil Saunders, September 2013