181
COOLING SYSTEM
COMPONENTS
9
Adapter/Inner Exhaust Housing
3-CYLINDER MODELS
• Adapts the cylinder/crankcase assembly (pow-
erhead) to the exhaust housing and the water
tube.
• Provides water passages which route incoming
and outgoing cooling water.
• Provides exhaust passages which connect to
the gearcase.
Pressure Relief Valve
A pressure relief valve is used to control water
flow and operating temperature at higher speeds
(above approximately 1800 RPM). The pressure
relief valve opens as water pressure increases.
Spring tension sets the opening pressure.
Overheating: A restricted or faulty valve typically
results in HIGH SPEED overheating.
Overcooling: Debris may prevent the valve from
closing completely.
Thermostat
The thermostat controls water flow and operating
temperature at lower speeds (below 1800 RPM).
Overheating: A restricted or faulty thermostat typ-
ically results in LOW SPEED overheating.
Overcooling: Debris may prevent the thermostat
from closing completely.
1. Megaphone
2. Exhaust housing
3. Water tube
4. Adapter housing
5. Inner exhaust housing
002436
Pressure relief valve components 002437
1. Cover and O-ring
2. Spring and thermostat
3. Cylinder head
4. Cylinder head seal
002439
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