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20 Generac
®
Power Systems, Inc.
• 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:
You must hold the rocker arm jam nut in place as
you turn the pivot ball stud.
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 you will
not be able 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.
• On GT-990, Repeat the process for the other cylinder.
4.9 COOLING SYSTEM
Air inlet and outlet openings in the generator com-
partment must be open and unobstructed for contin-
ued proper operation. This includes such obstruc-
tions 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 your
generator is 40° C (104° F).
4.10 ATTENTION AFTER SUBMERSION
If the generator has been submerged in water,
it MUST NOT be started and operated. Following any
submersion in water, have a Generac/Guardian
Authorized Dealer thoroughly clean and dry the gener-
ator.
4.11 CORROSION PROTECTION
Periodically wash and wax the enclosure using auto-
motive type products. Frequent washing is recom-
mended in salt water/coastal areas. Spray engine
linkages with a light oil such as WD-40.
!
Jam Nut
Pivot Ball
Stud
Rocker
Arm
Valve
Stem
Section 4 — Maintenance
Guardian Air-cooled 7 kW, 12 kW and 15 kW Generators