If your lawn mower is running bad or hard to start, adjusting the valves can make a
world of difference in how it starts and runs. The steps below will show you how to do
this on small engines with Overhead Valves (OHV)
Things you'll need:
- Set Of Allen Wrenches
- Set Of Feeler Gauges
- Spark Plug Socket & Ratchet
- The Valve Specs For Your Engine
1 This article pertains to a four stroke engine with Overhead Valves. First you
need to remove the valve cover and take the spark plug out of the engine. You
will need to be able to turn the flywheel either by hand, by the starter pull rope,
or use the starter. Put your thumb in the spark plug hole and turn the flywheel
until you feel pressure push your thumb out and this is the compression stroke.
Both valves should be closed. Now find top dead center on the piston.(TDC)
Stick a screwdriver in the spark plug hole until you feel the piston and slowly turn the
flywheel until the piston reaches the top and go about 1/4" past top dead
center.
2 Now you can check the valve clearances on both the intake valve and the
exhaust valve. You will need the valve clearance specs for your particular
engine. To adjust you must loosen the valve adjuster locks and then turn the
adjusting nut while you have the right feeler gauge in between the rocker arm
and the valve stem. You should feel a slight drag on the feeler gauge for the
proper set.
3 Most Briggs engines normally set at 003 to 005 on the intake and 005 to 007 on
the exhaust. The engine must be cold when setting the valves. You must hold the
adjuster while tightening the locking nut back down. Then check with the feeler
gauge again. Once you have them set properly then replace the valve cover
and spark plug and you should be good to go.
Tips To Remember:
Set the valve clearances when the engine is cold.
