Oxidation Catalytic Converter Protection From Unburned Gasoline (California Type Only); Fuel Cut-Off Solenoid Valve - Honda VT750C2 Shadow Spirit Service Manual

TECHNICAL FEATURE
OXIDATION CATALYTIC CONVERTER PROTECTION
FROM
UNBURNED GASOLINE (California type only)
OUTLINE
This motorcycle is equipped with heat-tube enhanced oxidation catalytic converters. Through the chemical reactions, they
convert HC and CO in the engine's exhaust to carbon dioxide (C02) and water vapor. If the unburned (raw) gasoline from
the combustion chamber flows into the catalytic converter, it will damage the catalytic converter through excessive tem­
peratures. A damaged catalytic converter cannot be effective for exhaust emissions control.
The fuel cut-off solenoid valve and heat-tube protect the oxidation catalytic converter from damage by raw gasoline.
FUEL CUT-OFF SOLENOID VALVE
CONSTRUCTION
Raw gasoline can enter the catalytic converter under the following conditions:
- The engine stop switch is turned to
"~"
suddenly while the engine is running.
- Ignition cut system (rev limiter) operates when the engine is over rewed.
The fuel cut-off solenoid valve is controlled by the ICM, and the float chamber air vent passage is changed according to
above described conditions.
The fuel cut-off solenoid valve consists of a coil and valve, and 3 passages.
1. Connection to sub air cleaner (atmosphere)
2.
Connection to throttle bore
3. Connection to float chamber air vent
The fuel cut-off solenoid valve opens passages 1 to 3 passage when there is no operation voltage.
OPERATION
Normal Operation (When the fuel cut-off solenoid valve does not operate):
1. No operation voltage from the ICM.
2. The float chamber air vent is open to atmosphere.
3. The float chamber pressure (surface of the gasoline in the float chamber) is atmosphere.
4. The carburetor operates normally.
Fuel Cut Operation (When the fuel cut-off solenoid valve operates):
1. The operation voltage comes from'the ICM.
2. The float chamber air vent passage is closed to atmosphere.
3. The float chamber air vent is opened to the throttle bore.
4. The float chamber pressure (surface of the gasoline in the float chamber) becomes negative.
5. The float chamber pressure will be same as throttle bore pressure.
6. The carburetor stops fuel supply.
VALVE
TO THROTTLE BORE
FUEL CUT-OFF
TO ATMOSPHERE
t
OPERATION
VOLTAGE
SOLENOID VALVE
CARBURETOR
/l------, FUEL CUT-OFF SOLENOID
~ VALVE DOES NOT·
OPERATE:
. . FUEL CUT-OFF SOLENOID
VALVE OPERATES:
2-2.