Generac GT-990 — Adjusting GT-990 Valve Clearance
Adjustments · Valve train
For the Generac GT-990, from the Generac owner's manual.
Applies to: Generac GT-990 engine
Procedure
- Make sure engine is at room temperature between 60 and 80 F.
- Make sure the spark plug(s) are removed.
- Remove the four valve cover screws with a #2 or #3 Phillips screwdriver.
- Rotate the engine by hand to bring the piston to Top Dead Center of its compression stroke.
- Loosen the rocker jam nut.
- Turn the pivot ball stud with a 10 mm allen wrench while checking clearance with a feeler gauge.
- Hold the pivot ball stud and tighten the rocker arm jam nut; recheck clearance.
- Install new valve cover gasket and re-attach valve cover.
- Re-attach the spark plug wire.
- Repeat the process for the other cylinder.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Correct valve clearance 0.002-0.004 inch (0.05-0.1 mm)
- Tighten the jam nut to 174 in.lbs. torque
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.