Briggs and Stratton 18.5 intek model 31p707 ,type 0123 E1. Changed head gasket last spring -set valves- and used all summer. started turning over harder but started. This spring not starting-too much compression to turn over fast enough-adjust valves multiple times - then replace cam shaft which has a auto compression release on it, valves are set correct and turns easy without spark plug in- still to much compression -oh yes new battery and starter and jumping directly to starter it still boggs down on compression stroke. Any ideas out there ??