LUBRICATION, MAINTENANCE AND TUNE-UP
recirculation) system. That would cut power a
great deal and probably damage the engine.
Periodic inspection of suction valve operation
is very important.
Check the suction valves with the engine
You can check the air suction valve function by
simply disconnecting the long suction hose at
the air cleaner housing (Figure 62). You should
be able to blow through this hose into the
exhaust system and you should not be able to
draw any air out of it because of the suction
valve reeds. If you can draw air out of the hose,
one or more of the suction valves is faulty.
T o remove and inspect each suction valve
Suction System in Chapter
Normal wear of the valves and valve seats
decreases valve clearance and alters valve
timing slightly. Insufficient valve clearance can
lead to burnt valves and seats and will
eventually cause serious engine damage.
Excessive clearance causes noisy operation and
more rapid valve train wear.
Engines that use overhead camshafts with
shims to adjust valve clearance should not
require frequent valve clearance adjustment,
but the clearance must be inspected according
to the maintenance schedule (Table 1).
Inspection is a simple, easy task compared to
Check and adjust valve clearance with
the engine cool, at room temperature.
S o m e fuel m a y spill during these
procedures. Work in a well-ventilated
area at least 50 feet ,from any sparks or
.flames, including gas appliance pdot
lights. Do not smoke in the area. Keep a
ratedfire extinguisher handy.
1. Check that the ignition switch is
2. Remove the fuel tank; see
Fuel T a n k
R e m o v a l in Chapter Seven.
Remove the valve cover; see Valve Cover
R e m o v a l in Chapter Four.
4. Check that all 16 camshaft cap bolts (Figure
63) are properly tightened to
5. Remove the timing cover and gasket from
the lower right side of the engine (Figure 64).
6. Turn the crankshaft clockwise with a 17 mm
wrench on the outer advancer bolt (Figure 65)
until one of the cam lobes is pointing directly
away from its valve (Figure 66).
Do not use the small inner bolt to turn
the engine or you will damage the
ignition advance mechanism.
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