Generac 8.1 GN — Valve Lash Adjustment
Adjustments · Valve clearance
For the Generac 8.1 GN, from the Generac owner's manual.
Applies to: Generac 8.1 GN, Generac GH-410 engine, Generac GT-530 engine, Generac GT-990 engine, Generac GT-999 engine
Before you start
- Make sure the engine is at 60 to 80 F (16 to 27 C).
- Hold the rocker arm jam nut in place as the pivot ball stud is turned.
- Start all four screws before tightening.
Procedure
- Ensure engine is cool before checking; if 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.
- Ensure piston is at Top Dead Center of its compression stroke (both valves closed).
- Remove the four screws attaching the valve cover.
- Loosen the rocker jam nut; turn the pivot ball stud while checking clearance with a feeler gauge.
- Hold the pivot ball stud in place with the Allen wrench and tighten the rocker arm jam nut to 174 in-lb (19.68 N-m).
- Recheck valve clearance to make sure it did not change.
- Install new valve cover gasket and re-attach the valve cover.
- 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.
Tools required
- 10 mm Allen wrench (530 cc engine) Amazon
- 13 mm Allen wrench (410, 990 and 999 cc engines) Amazon
- feeler gauge Amazon
- socket wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Correct clearance is 0.002-0.004 in (0.05-0.1 mm)
- Jam nut torque 174 in-lb (19.68 N-m)
- Valve cover fasteners 6-9 ft/lb (8-12 Nm)
- Spark plugs 15-18 ft/lb (20-25 FridayParts $42.95 Nm)
Full service-parts list: Generac 8.1 GN →
Source: Generac owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.