Sounds like an L-head Briggs and Stratton. Simply take a wrench and check cylinder head bolts for tightness, and tighten evenly. Just because it is blowing some white smoke while only cutting high grass does not necessarily mean head gasket needs to be replaced. So no smoke while cutting under normal conditions? How much does it smoke when it does smoke? Did it just start smoking?Just blowing some white smoke when cutting some high grass otherwise none. May be the head gasket since in the process of removing the top to fix some things, like recoil, may have loosened the head bolts. Did tighten but no torque. Well maintained. Replace head gasket?