Small Engines (Lawn Mowers, etc.): 17.5 hp Briggs & Stratton hard cranking, twin cylinder engine, briggs stratton

Question
I have a 17.5 hp Briggs & Stratton twin cylinder engine on a riding mower. The engine turns over very slowly, similar to having a weak battery or bad starter. The battery is charged and strong. Is it possble to adjust the valves on this engine? If so how can this be done? If not any ideas you may have on fixing the problem would be appreciated. The model is 42A707 and the type is 2653E1. Thanks Stuart

Answer
It is most likely not valve adjustment.  Did you measure the voltage in the battery?  A fully charged 12 volt battery should read 12.6 volts.  If you remove the spark plugs and turn it over is it free?  If it is I think it is the battery or a connection loose or corroded.  If not then it is internal to the engine.  Crankshaft pr rod bearings or something else binding up the engine.