Valve Mechanism - Kubota EA330-E4 Series Workshop Manual

EA330-E4, WSM

[2] VALVE MECHANISM

This engine adopts the overhead valve (OHV)
mechanism. The intake and exhaust valves (7), (1) open
and close as follows:
1. The crankshaft rotation is transmitted to the
camshaft via the timing gears (crank gear (12), cam
gear (10) and idle gear (11)).
2. The cam actuated by the rotation of the camshaft
push up the tappet (8) and push rad (6), and the
rocker arm (3) rocks with the rocker arm shaft as an
axis like a seesaw and overcomes the tension or the
valve spring (5), allowing the valve to open.
3. When the convex portion of the cam passes its top,
the valve closes by the spring tension.
Since the intake / exhaust valves expand due to heat
during engine running, a small clearance (valve
clearance) is provided between the end of rocker arm (3)
and the valve cap (2) in cold condition to prevent
compression leak caused by the valve pushing-up. This
clearance is adjusted with an adjusting screw (4)
mounted on the rocker arm.
The intake / exhaust valves are made of heat
resisting steel, and induction hardened at the valve stem
ends for improved wear resistance. The valve cap is
forged and carburized, and induction hardened at the
contact section with the valve cap of the rocker arm for
improved wear resistance. The valve springs (5) are
made of piano wires and its surfaces is performed
shot-peening for greater fatigue strength.
(1) Exhaust Valve
(2) Valve Caps
(3) Rocker Arms
(4) Adjusting Screw
(5) Valve Spring
(6) Push Rod
1) Valve Guide
The valve guides are cast iron and reamer-finished
after being pressed into the cylinder head. The lower
area of the exhaust valve guide has a carbon cutter
which prevents carbon adhesion to the valve.
(1) Exhaust Valve Guide
(2) Carbon Cutter
1-M4
ENGINE
(7) Intake Valve
(8) Tappet
(9) Camshaft
(10) Cam Gear
(11) Idle Gear
(12) Crank Gear
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(3) Intake Valve Guide
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KiSC issued 05, 2015 A