Make sure the piston is at top dead center (TDC) on the compression stroke. To do this, remove the spark plug. While looking inside the spark plug hole, turn the engine over by slowly pulling the recoil starter or turning the crank by hand. As you do this, you will see the piston go up and down. Stop the piston when it is closest to the spark plug hole. Both valves should be closed. This is TDC.

Remove the valve cover. Slide the rocker arms off of the valves and turn them to the side. You do not need to remove the rocker arms. Just turn them to the side. Use a length of rope to stuff into the combustion chamber, through the spark plug hole. Fill the chamber with as much rope as you can push in there. This will prevent the valves from dropping into the chamber.

Push the valve spring and retainer down and position them so you can slide them up, off of the tip of the valve. Now replace the stock valve springs with stiffer valve springs. We use 18lb valve springs with stock cams and 26lb springs with high performance cams. Slide the rocker arms back over the valves. Remove the rope from the chamber.

Now you need to use a feeler gauge to set the valve lash. This is the distance between the rocker arm and the valve. Make sure your engine is still set at TDC before setting the valve lash. We set our valve lash at 0.002" intake and 0.003" exhaust. After the valve lash has been set, turn the engine over a few times and recheck. When everything checks out okay, you can put the valve cover back on, remove the rope and install the spark plug.