Yamaha YTZ250S 1986 Service Manual page 76

3. Inspect the cooling system for leaks. At-
tach the cap tester to the radiator and
pump it to the specified pressure. If the
pressure gauge drops, inspect all hoses,
fittings and radiator for an external leak.
If leakage is found, repair or replace defec-
tive parts.
Pressure:
98.1
kPa
(1.0
kg/cm 2 ,
14.2
psi)
4. Using the cap tester, check that the
radiator cap vacuum valve and pressure
valve operate correctly. Measuring with
a tester, apply the specified pressure for
10
seconds, and make sure there is no
pressure drop.
If the air pressure shows a drop, replace
the radiator filler cap.
Valve opening pressure:
93.2-122.6
kPa
(0.95-1.25
kg/cm 2 ,
13.5
-17.8 psi)
3-35
5. Suspend thermostatic valve in a vessel of
water that contains a reliable ther-
mometer.
Heat the water slowly. Then note the ther-
mometer reading while stirring the water
continually.
The thermostatic valve should begin to
open at 63-67°C (145.4-152.6°F).
1. Thermometer
2. Full open
3. Begin to open
--CD
(2)
80°C (176°F)
--(3)
63 - 67°C (145.4-152.6°F)
1====;jJ._@
~~*--®
@
4. Water
5. Thermostatic valve
6. Vessel
OPEN
- - - - - - - - : : 1 .....
-1
7mm (0.28 in)
CLOSE--~~----+---~
65°±2°C 80°C
(149°±35.6°F) (176°F)
NOTE: ______________________ _
Thermostat is sealed and its setting is specializ-
ed work. Always replace if its accuracy is in
doubt. A faulty unit could cause serious
overheating or overcooling.