CARBURETOR ADJUSTMENTS
The carburetor of the engine is pre-set at the factory. The carbure-
tor should not be tampered with because it would violate EPA and
CARB regulations and
VOID THE EMISSION CONTROL SYSTEM
WARRANTY
.
CHECKING AND ADJUSTING VALVE CLEARANCE
Check valve lash and adjust (if necessary) after the first 50 hours
of operation and every 100 hours thereafter.
IMPORTANT
: If not qualified for doing this procedure or the proper
tools are not accessible, please take the engine/equipment to the
nearest Authorized Service Center to have the valve clearance
adjusted. This is a very important step to insure a long life for the
engine.
To adjust valve clearance:
• Make sure the engine is at room temperature.
• Remove spark plugs and make sure that the spark plug wires
are out of the way.
• Remove the four screws attaching the valve cover with a 10
mm wrench or socket.
• Make sure the piston is at Top Dead Center (TDC) of its com-
pression 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 ratchet and a 36 mm socket
to rotate the engine in a clockwise direction. While watching
the piston through the spark plug hole, the piston should be
observed moving up after the intake valve closed. The piston is
at TDC when it is at its highest point of travel.
• Loosen the rocker jam nut (Figure 11). Use a 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 (0.05-0.1mm) for both
intake and exhaust valves.
Figure 11 — Adjust Valve Clearance
NOTE:
The rocker arm jam nut must be held 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 168 in/lbs. (19 Nm) torque. After
tightening the jam nut, recheck valve clearance to make sure it
did not change.
• Install new valve cover gasket.
• Re-install the valve cover and torque to 60 in/lbs (6.8 Nm).
NOTE:
Start all four screws before tightening, then torque in a criss-
cross pattern. Make sure the valve cover gasket is in place.
• Re-install spark plug.
• Re-attach the spark plug wire to the spark plug.
• Repeat the process for the other cylinder.
MAINTENANCE SCHEDULE
The owner/operator is responsible for making sure that all peri-
odic maintenance tasks are completed on a timely basis; that all
discrepancies are corrected; and that the equipment is kept clean
and properly stored. Never operate a damaged or defective engine.
Disconnect the spark plug wires from the
spark plugs, and place the wires where they
cannot come in contact with the spark plugs
before working on this engine.
8
Maintenance
Summary of Contents for GTH - 990
Page 13: ...11 Notes...
