Yanmar 3JH4E, Service Manual

Page: 83 / 350

2. Inspection and adjustment
63R1
2) If necessary, adjust the V-belt tension
(deflection). To adjust the V-belt tension,
loosen the set bolt for the belt adjuster and
move the alternator to tighten the V-belt.
3) Visually check the V-belt for cracks, oiliness
or wear. If any, replace the V-belt with new
one.
[NOTICE]
When the V-belt will be replaced with new one,
loosen the set bolt and move the alternator and
also loosen the V-pulley set bolts for the
cooling water pump. Remove the V-belt.
After replacing with a new V-belt and adjusting
the tension, run the engine for 5 minutes and
readjust the deflection to the value in the table
above.
(5) Checking and adjusting intake/exhaust
valve clearance.
Measure and adjust while the engine is cold.
Valve clearance is defined as follows:
• 2 valves system (3JH4E, 4JH4E):
gap between valve cap and rocker arm.
• 4 valves system (4JH4-TE, 4JH4-HTE):
gap between valve bridge and rocker arm.
On both systems, clearance can be adjusted
by the screw on the rocker arm.
1) Valve clearance measurement
a) Remove the rocker arm cover above
cylinder head.
b) Set the No.1 cylinder (Flywheel side) in the
compression Top Dead Center (TDC).
Turn the crankshaft to bring the piston of the
No.1 cylinder to its compression top dead
center while watching the rocker arm
motion, the timing mark of the flywheel
housing and the top mark of the flywheel.
(Position where both the intake and exhaust
valves are closed, no movement of both
intake and exhaust rocker arms.)
Notes:
• The crankshaft shall be turned clockwise
as seen from the gear case side.
• The cylinder number is counted from
flywheel side. At compression TDC, intake
and exhaust valves should have clearance,
which can be checked by hand. Also see
that the top mark on the flywheel aligns
with the mark on the flywheel housing. If
there is no valve clearance, remove
cylinder head and inspect the valve seat,
since the valve seat may be worn
abnormally.
Adjust the V-belt tension
inserting a bar
Belt adjuster
Set bolt
Alternator
010422-00E
Matching mark
Flywheel housing
1
010611-00E