Clean Air System
Vacuum Switch Valve Installation
Install the vacuum switch valve so that the vacuum fitting
[A] faces left side.
Route the hoses correctly (see Appendix chapter).
Vacuum Switch Valve Test
Vacuum Switch Valve (see Vacuum Switch Valve Re-
Connect a vacuum gauge [A] and syringe [B] or fork oil
level gauge to the vacuum hoses as shown.
Special Tool - Fork Oil Level Gauge: 57001-1290
Air Flow [C]
Gradually raise the vacuum (lower the pressure) applied
to the vacuum switch valve, and check the valve opera-
tion. When the vacuum is low, the vacuum switch valve
should permit air to flow. When the vacuum raises to
valve closing pressure, it should stop air flow.
Low Vacuum [D]
Secondary Air Flow [E]
If the vacuum switch valve does not operate as described,
replace it with a new one.
To check air flow through the vacuum switch valve, just
blow through the air cleaner hose.
Vacuum Switch Valve Closing Pressure (Open → Close)
Standard: 41 ∼ 49 kPa (310 ∼ 370 mmHg, 6.0 ∼ 7.1 psi)
High Vacuum [A]
Secondary air cannot flow [B]
Clean Air System Hose Inspection
Be certain that all the hoses are routed without being flat-
tened or kinked, and are connected correctly to the air
cleaner housing, vacuum switch valve, #1 and #4 carbu-
retor holders and air suction valve covers.
If they are not, correct them. Replace them if they are
ENGINE TOP END 5-11