Honda Gold Wing GL1200D Shop Manual page 396

~HONDA
~GL1200D'GL1200A
• Operation
When the camshaft lobe is not lifting the rocker
arm, the tappet plunger is at rest. In this position
its oil inlet hole aligns with the tappet body oil
inlet hole. Oil enters the tappet reservoir through
these holes.
As the assist shaft pushes on the rocker arm shaft,
the eccentric rocker arm shaft is rotated. As a result,
the rocker arm is held by the valve stem and cam-
shaft; that is, the valve clearance is naught (zero).
As the camshaft turns and lifts the rocker arm to
open the valve, the eccentric rocker arm shaft
revolves. The shaft pushes the tappet plunger down
and oil pressure in the tappet high pressure chamber
increases causing the check valve to close.
As the cam lobe nears maximum lift, oil pressure in
the high pressure chamber increases rapidly (because
the check valve is closed). The high oil pressure
keeps the check valve against the plunger. At the
same time the rocker arm is pushing against the
tappet plunger. This causes a very small amount of
oil to leak out of the high pressure chamber bet·
ween the plunger and body. This allows the plunger
to absorb the shock from the effects of the cam
lobe reaching maximum lift.
After the cam lobe passes maximum lift, the engine
valve springs force the engine valve to close and to
push against the rocker arm which follows the cam
profile. This also causes the eccentric rocker arm
shaft to change direction allowing the tappet
plunger to be pushed up by the spring in the high
pressure chamber. Oil pressure decreases as a result,
the check valve leaves its seat and the plunger and
body oil inlet holes realign allowing oil to re-enter
the reservoir and high pressure chamber.
At the same time, the assist shaft causes the
eccentric rocker arm shaft to rotate. As this hap-
pens, the rocker arm is held by the valve stem and
camshaft.
All of the above actions keep valve clearance at zero
under all normal operating conditions.
TECHNICAL FEATURES
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