Adjusting Tappet Clearances & Overhead Valves
How to Adjust Tappet Clearances
Since lapping valves removes a small amount of material from the surfaces of the valve face and valve seat, you may need to adjust the tappet clearances - the spacing between the valve stem and the tappet - after lapping and reinstalling the valves. Ask your Briggs & Stratton Authorized Dealer near you for the correct tappet clearance for your engine.
Step 1: With each valve installed in its proper guides in the cylinder, turn the crankshaft (clockwise as viewed from the flywheel end of the crankshaft) to top dead center. Both valves should be closed. Then, turn the crankshaft past top dead center until the piston is 1/4" down from the top of the cylinder.
Note: This procedure should be repeated for each cylinder on Opposed Twin and V-Twin engines.
Step 2: Check the clearance between each valve and its tappet, using a feeler gauge
Step 3: If clearance is insufficient, remove the valve and grind or file the end of the valve stem square to increase the clearance. Check the length frequently as it is easy to remove too much metal.
Step 4: Once the individual valve parts have been thoroughly cleaned, lubricate the valve stems and guides, using valve guide lubricant. Then, make certain there is NO lubricant on the ends of the valve stems or tappets.