The exhaust control system (excs) consists of the exhaust control valve (excv), exhaust control valve actuator (excva) and exhaust control valve cables (excv cables).
Excv is installed in the exhaust pipe. Excva is mounted inside of the right frame. The excv is operated by the excva via the cables. This system is designed to improve the engine torque at low engine rpm.

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Exhaust control system operationCrankcase breather (pcv) hose / reed
valve / cover removal and installation
Removal
Lift and support the fuel tank with the prop stay.
Refer to “fuel tank removal and installation” in section 1g .
Remove the air cleaner box. Refer to “air cleaner box removal and
installation” in section 1d .
Disconnect the crankcase breather (pcv) hose (1).
...
Cylinder head disassembly and assembly
Refer to “engine top side disassembly” .
Refer to “engine top side assembly” .
Caution
identify the position of each removed part.
Organize the parts in their respective groups
(i.E., Intake, exhaust, no. 1 Or no. 2) So that
they can be installed in their original
locations ...
Pair reed valve removal and installation
Removal
Lift and support the fuel tank with the prop stay.
Refer to “fuel tank removal and installation” in section 1g .
Remove the air cleaner box. Refer to “air cleaner box removal and
installation” in section 1d .
Remove the pair control solenoid valve (1) along with the ...