Xinchai 490B Series Manual page 29

4.1 Tightening Sequence of Cylinder Head Bolts
The cylinder head is fixed on the cylinder block with cylinder head bolts. When
tightening these bolts, torque wrench should be used and the specified tightening torque
value should be reached step by step following the tightening sequence shown in the figure.
If the cylinder head has been dismantled and remounted, the engine should be shut down
and the cylinder head bolts should be re -tightened to the specified tightening torque as
well as the valve clearances should be re-adjusted after the engine is warmed up in its first
running
4.2 Checking and Adjustment of Driving Belt
1冤尧 Check the whole belt and renew the broken belt.
2冤尧 Engine should work 15 minutes after the new belt is installed and then check the
tightening of belt.
3冤尧 Driving belt should be kept under a certain tension status. Normally when exerting
a force of 29耀49N at the middle part of the belt a depressed distance not exceeding 10耀
15mm is recommended. Too tight belt will lead to excessive wear of bearings in generator,
fan and water pump. Too loose belt will lead to drop of speeds of accessories. As a
consequence, voltage from generator, air flow from fan and/or water flow from water
pump will drop and normal function of the engine will be affected.
4冤尧 Adjust tension of belt:
荫 Loosen two fixing bolts.
荫 Turn the generator to the right or left to adjust the tension of belt until it reaches
an appropriate value.
荫 Tighten the two bolts.
4.3 Notes about Thermostat
银
Note: it's prohibited to operate an engine without a thermostat.
When the temperature of the coolant through the thermostat reaches about 70益, the
thermostat valve should open, and it should fully open when the temperature reaches 85益.
When checking the thermostat, if necessary, thermostat may be put into water and
heat it up gradually, and then check the open temperature and fully open temperature of
thermostat valve to see whether they are in the range specified above.
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