MTD 556 - Manual (Page 15)

HOW YOUR LOG SPUTTER OPERATES
THE PUMP
A two-stage log splitter pump has one large and one
small gear section, using common inlet and outlet
ports. Below a preset pressure (called unloading pres­
sure) a check valve between the two gear sections
allows both flows to combine. Together, the two gear
sections create a large volume flow which produces
rapid cylinder movement under low load conditions.
Above unloading pressure, a pilot pressure line (which
simulates actual pressure at the cylinder) activates the
unloading valve, which causes the flow to bypass the
large gear section and return to the pump inlet area.
The small gear section is now operating alone, and will
generate the higher pressure necessary for the actual
log splitting operation.
The original factory setting for the unloading valve is
designed to provide maximum flow while remaining
below engine stalling load. Note: Splitting capability
is not affected by the setting of the unloading
valve. Do not attempt to adjust or reset it without a
pressure gauge (should be performed by an autho­
rized service dealer only).
THE DIRECTIONAL VALVE AND CYLINDER
From the pump, oil flows to a four way, three position
directional valve. At the neutral position this valve
directs the flow back to the oil reservoir, bypassing the
cylinder. When the directional valve is directing the
flow to the back of the cylinder, the cylinder rod
extends quickly until it meets significant resistance.
Upon reaching unloading pressure, movement of the
shaft will slow but will continue forward. If the pressure
reaches a preset maximum (called relief valve pres­
sure) the relief valve, located within the directional
valve, will allow the flow to bypass the cylinder and
return to the reservoir. This can happen when the cyl­
inder rod meets excessive resistance, or when it
reaches the end of its stroke and can move no farther.
NOTE: Never operate at relief valve pressure for more
than a few seconds.
When the directional valve is directing the flow to the
front of the cylinder, the rod will retract quickly since it
is encountering no resistance. The relief valve will
momentarily bypass the flow at the end of the return
stroke but the directional valve should then automati­
cally return to the neutral position, directing the flow
directly into the reservoir. This serves to protect the
pump from possible damage due to prolonged opera­
tion at relief valve pressure.
Because of the potential for system damage, the relief
valve is carefully and precisely preset by the manufac­
turer.
NOTE: The user should not attempt to adjust or
change the setting of the relief valve.
OPERATIDNAL PRDBLEMS
If you have trouble with your log splitter, please refer to
the Hydraulic Trouble Shooting Guide.
NOTE: Readjustment of valves or disassembly of
pump should be performed by an authorized ser­
vice dealer only.
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