How to Set Valves in Small Engines

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This valve adjustment procedure is for the Briggs and Stratton single OHV model with overhead valves. Two models of engines were manufactured that came with valve adjusting systems. One was the OHV (overhead valve) engine, and the other was the L Head engine. The OHV model came in the twin-cylinder engine as well, and both are used in bigger equipment like garden tractors, riding lawnmowers, weed whackers and rototillers.

Things You'll Need

  • Tools required:
  • A set of open-end wrenches
  • Screwdriver
  • Spark plug wrench
  • A set of feeler gauges
  • Silicone gasket sealer

Adjusting The Valves

  • Before dismantling your engine, remove the spark plug. Set your piston at top dead center at compression. This can be done by plugging the spark plug hole with your finger. As you slowly click the engine with your ignition key, you will be able to feel compression build up in the cylinder. At this point the piston should be at top dead center. Loosen the brake release spring, usually located on the side of the head close to the valves.

  • Take the valve cover off. By now, both valves should be exposed. When attempting to do a valve adjustment on a small engine you always start with the intake valve first, followed by the exhaust. The intake valve should be in the closed position. The cam lobe and tappet, also known as the rocker arm, should be in the downward position. Loosen the lock nut on the tappet by turning it counterclockwise. Set your feeler gauge at the recommended settings of .002 (0.05 mm) to .004 (0.10 mm). Insert the feeler gauge between the tappet and the cam lobe to start the adjustment. Use a screwdriver to turn the center adjusting screw clockwise in the tappet arm until it sits firmly on the feeler gauge. Hold the screwdriver in place, and then tighten the lock nut. Don't over-tighten it.

  • Use the same procedure to set the exhaust valve. The settings are the same. Both valves are now adjusted. Tighten the brake release spring and reassemble the engine.

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