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20 Generac
®
Power Systems, Inc.
4.8 ADJUSTING VALVE CLEARANCE
After the first 50 hours of operation, adjust the valve
clearance in the engine.
Important: If feeling uncomfortable about doing this
procedure or the proper tools are not available, contact
the nearest Generac Authorized dealer for service assis-
tance. This is a very important step to insure longest life
for the engine.
To adjust valve clearance:
• Make sure the engine is at room temperature.
• 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 with
a #2 or #3 phillips screwdriver.
• 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. While watching the piston
through the spark plug hole. The piston should move
up and down. The piston is at TDC when it is up as
high as it can go.
• Loosen the rocker jam nut. Use an 10mm allen
wrench to 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
inch (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/lbs. torque.
After tightening the jam nut, recheck valve clearance to
make sure it did not change.
Figure 4.10 - Valve Clearance Adjustment
• 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.
• Re-attach the spark plug wire to the spark plug.
• Repeat the process for the other cylinder.
4.9 COOLING SYSTEM
Air inlet and outlet openings in the generator compart-
ment must be open and unobstructed for continued
proper operation. This includes such obstructions as
high grass, weeds, brush, leaves and snow.
Without sufficient cooling and ventilating air flow, the
engine/generator quickly overheats, which causes it to
quickly shut down. (See Figure 4.9 for vent locations.)
Figure 4.9 – Cooling Vent Locations
The exhaust from this product gets extremely hot
and remains hot after shutdown. High grass,
weeds, brush, leaves, etc. must remain clear of
the exhaust. Such materials may ignite and burn
from the heat of the exhaust system.
The maximum ambient temperature for the
generator is 48.9° C (104° F).
!
Jam Nut
Pivot Ball
Stud
Rocker
Arm
Valve
Stem
Section 4 — Maintenance
Generac Air-cooled 7 kW, 12 kW and 15 kW Generators