19. EVAPORATIVE/EXHAUST EMISSION
CONTROL SYSTEM
EXHAUST EMISSION CONTROL SYSTEM
The exhaust emission control system adopted in this model utilizes the reed valve to draw
secondary air into the exhaust system for re-combustion by means of exhaust pulsation so as to
minimize the exhaust emission.
FUNCTION
Item
Purpose Function
Secondary Air
Cleaner
Filter secondary air.
It filters the fresh air drawn for re-burning to
prevent dirt or dust from affecting the operation of
the air injection cut-off valve.
Air Injection
Cut-off Valve
Prevent exhaust
muffler noise and
backfiring at sudden
deceleration.
The air injection cut-off valve usually opens to
lead air into the exhaust muffler in which air is
re-burned to reduce CO. When the throttle valve
closes suddenly, the air injection cut-off valve is
actuated by vacuum to close and cut off secondary
air in order to prevent exhaust muffler backfiring
due to air in the exhaust system.
Reed Valve
Control the secondary
air inlet to reduce CO.
When the motorcycle speed is less than 50km per
hour, the reed valve operates to draw secondary air
into the exhaust system for re-combustion.
TROUBLESHOOTING
High CO at idle speed
1. Damaged or clogged reed valve
2. Damaged or clogged air injection cut-off valve
3. Clogged air cleaner
Backfiring at sudden deceleration
1. Damaged reed valve (malfunction)
2. Faulty air injection cut-off valve (unable to close)
3. Carburetor incorrectly adjusted
4. Faulty air cut-off valve
5. Leaking vacuum tube
Exhaust muffler noise
1. Faulty air injection cut-off valve
2. Broken vacuum tube
3. Reed valve failure
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