Have Kohler 17hp engine on lawn tractor. Made knocking noise all last summer and finally died and now won't start. Am new to small engine repair. My son and I are tearing apart together to see how engine is built and hopefully get lucky to fix it without having to pay big $. Have repair manual that tells me how to remove Cam shaft but not where to get at it. Do I get at from top of engine by removing fly wheel? Or do I get at it by removing oil pan on bottom of engine? Or do I remove head and come at it by removing piston first? Anyone help?