Take the cover off the top of the engine. remove the nut that holds the flywheel on. take a wheel puller and take the flywheel off the sheer key is in the gap on the crankshaft. put the flywheel back on align the slots up and insert new shear pin put nut back on and covers. be sure the blades were not damaged. some people use a crow bar to pop off the flywheel and hit the crankshaft with a hammer. i don't advise it because you can damage the threads on the crankshaft. good luck