Small Engines (Lawn Mowers, etc.): 18 hp B&S engine, starter solenoid, compression release

Question
Engine turns slow with spark plugs in. If out turns fine. I have cleaned all electrical connectors and am using a car battery.  Still turns slow and won't start.

Answer
Different conditions will cause this, one is hydro-lock, thats when you try to start a engine for so long it floods itself so badly that the cylinder is full of fuel, and it can't compress it. Remove the spark plug and turn it over severals times to expel the fuel from the cylinder. Second is the compression release system. This is a cam driven release in the crankcase that allows some compression ti release from the cylinder as it tries to start, then closes itself off once it does......Although a weak starter can be to blame, or a bad solenoid. For sometime I was under the impression a starter solenoid was either good, or bad, that wasn't the case a few months back, I had one that was letting some power by the switch, but not enough for it to turn over fast enough.....Tom