the exhaust gas pulses to introduce fresh air
into the exhaust ports.
The vacuum switch (Figure 36) normally
allows fresh air pulses into the exhaust ports
but shuts off air flow during engine braking.
This helps prevent backfiring in the exhaust
system due to the greater amount of unburned
fucl in the exhaust gas during deceleration.
The air suction valves. on top of the valve
cover. are basically check valves. They allow
the fresh air to enter the exhaust port and
prevent any air or exhaust from reversing back
into the system.
Suction Valve Removal/Installation
If the engine idle is not smooth, if engine
power decreases seriously or if there are any
abnormal engine noises. remove the air suction
valves and inspect them.
Sorne fuel may spill during these
procedures. Work in a well-ventilated
area at least 50.feet frorn any sparks or
James, including gas appliance pilot
lights. Do not smoke in the area. Keep a
BC ratedjire extinguisher handv.
1. Check that the ignition switch is
Remove the fuel tank as described in this
Slide up the lower hose clamps and pull the
hoses offthe air suction valve covers
37). Swing the vacuum switch and air hoses up
out of the way.
4. Remove the bolts securing the air suction
valve covers (Figure 37).
5. Remove the covers and pull the valves up
out of the valve cover (Figure 38).
Check the suction valves for cracks, folds.
warpage or any other damage (Figure
7. Check the sealing lip coating around the
perimeter of the assembly. It must be free of
grooves, scratches or signs of separation from
the metal holder.
The valve assembly cannot be repaired
must be replaced (damaged.
Wash off any carbon deposits between the
reed and the reed contact area with solvent.
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