Generac — Adjusting GT-990 Valve Clearance

For these Generac models: 04916-0, Air-cooled 11 kW Generators.

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Procedure

1. Make sure the engine is at room temperature (between 60° and 80° F).
2. Make sure that the spark plug(s) are removed.
3. Remove the four screws attaching the valve cover with a #2 or #3 phillips screwdriver.
4. Make sure the piston is at Top Dead Center (TDC) of its compression stroke (both valves closed).
5. Loosen the rocker jam nut and use an 10mm allen wrench to turn the pivot ball stud.
6. Check clearance between the rocker arm and the valve stem with a feeler gauge.
7. When valve clearance is correct, hold the pivot ball stud in place and tighten the rocker arm jam nut to 174 in.lbs. torque.
8. Recheck valve clearance to make sure it did not change.
9. Install new valve cover gasket and re-attach the valve cover.
10. Re-attach the spark plug wire to the spark plug.
11. Repeat the process for the other cylinder.

Source: manual:GeneracPowerSystems0049160UsersManual559844.1133830900.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.