Thermostat; Fan Belt - Shibaura ST450 Operator's Manual

Thermostat

The thermostat (1) in Figure 3-26, is a
heat-sensitive valve located in the coolant outlet
connection in the front of the cylinder head.
When the engine is cold, the thermostat shuts off
the flow of coolant to the radiator, allowing for
rapid engine warm-up. A recirculating bypass
allows coolant to circulate inside the engine
whenever the thermostat shuts off flow to the
radiator.
IMPORTANT: Do not attempt to improve cooling
by removing the thermostat. This will cause the
engine to run below normal working temperatures,
resulting in excessive engine wear.
To install a new thermostat (1) in Figure 3-26,
position it in the recess of the water outlet
connection so that the heat element (spring end)
is in the cylinder head of the engine.

Fan Belt

NOTE: Check the condition of the fan beIt after
every 50 hours of operation. Check fan belt
tension after every 200 hours of operation.
A belt-driven fan located at the front of the engine
draws air through the fins of the radiator to lower
the temperature of the radiator coolant.
When 5 kg of thumb pressure is applied to the
belt midway (1) in Figure 3-27, between the belt
pulleys, a correctly tightened belt will deflect 5 -
10 mm.
If the fan belt is slipping, fan efficiency is lowered,
resulting in the engine running too hot. If the belt
is too tight, the life of the alternator bearing will be
shortened. If the fan belt shows signs of cracking
or fraying, install a new belt.
To adjust fan belt tension:
WARNING
Never attempt to loosen or tighten mounting
bolts while the engine is running.
1. Loosen the alternator mounting bolts (1) in
Figure 3-28.
2. Pry the alternator away from the engine and
tighten the mounting bolts.
SECTION 3 – LUBRICATION AND MAINTENANCE
3. Recheck belt deflection.
3-18
Figure 3-26
Figure 3-27
Figure 3-28