Valve Lash Adjustment - Generac Power Systems Automatic Standby Generator Owner's Manual

4.6 — Valve Lash Adjustment
After the first 25 hours of operation and then after every 400 hours of operation, check the valve clearance. Adjust if necessary.
Important: Please contact the Dealer for service assistance. This is a very important step to ensure longest life for the engine.
To check valve clearance:
• The engine should be cool before checking. If valve clearance is 0.002 - 0.004 in (0.05 - 0.1 mm), adjustment is not needed.
• Remove spark plug wires and position wires away from plugs.
• Remove spark plugs.
• Make sure the piston is at Top Dead Center (TDC) of its compression stroke (both valves closed). To get the piston at TDC, remove the intake
screen at the front of the engine to gain access to the flywheel nut. Use a large socket and socket wrench to rotate the nut and hence the
engine in a clockwise direction. While watching the piston through the spark plug hole. The piston should move up and down. The piston is at
TDC when it is at its highest point of travel.
To adjust valve clearance (see Figure 4-4):
• Make sure the engine is at 60 ° to 80 °F (16 ° to 27 °C).
• Make sure that the spark plug wire is removed from the spark plug and out of the way.
• Remove the four screws attaching the valve cover.
• Loosen the rocker jam nut. Using a 10 mm Allen wrench (530 cc engine) or a 13 mm Allen wrench (410 cc, 990 cc and 999 cc engines), turn
the pivot ball stud while checking clearance between the rocker arm and the valve stem with a feeler gauge. Correct clearance is 0.002-0.004
in (0.05-0.1 mm).
NOTE: Hold the rocker arm jam nut in place as the pivot ball stud is turned.
• When valve clearance is correct, hold the pivot ball stud in place with the Allen wrench and tighten the rocker arm jam nut. Tighten the jam nut
to 174 in-lb (19.68 N-m) torque. After tightening the jam nut, recheck valve clearance to make sure it did not change.
• Install new valve cover gasket.
• Re-attach the valve cover.
NOTE: Start all four screws before tightening or it will not be possible to get all the screws in place. Make sure the valve cover gasket
is in place.
• Torque fasteners to 6-9 ft/lb (8-12 Nm)
• Install spark plugs. Torque to 15-18 ft/lb (20-25 Nm).
• Re-attach the spark plug wire to the spark plug.
• Repeat the process for the other cylinder, if necessary.
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