Service Manual

HYDRAULIC DRIVE SYSTEMS
5 - 6 Mid-Size Walk Behind Service Manual
5. Thoroughly clean the area around each of the
charge pump housings.
6. To “prime” charge pump, loosen two hex socket
head capscrews (Figure 76) 1-1/2 turns only.
Make sure engine is not running. Lift charge pump
housing upward and wait for a steady flow of oil to
flow out from under housing. Retighten
capscrews. Do this for both pumps.
Note: Hydraulic reservoir can be pressurized to up to
5 psi to speed this process.
7. If either drive wheel still does not rotate, stop and
repeat steps 4, 5, and 6 on the respective pump. If
wheels rotate slowly, the system may prime after
additional running. Recheck hydraulic fluid level.
8. Allow unit to run several minutes after the charge
pumps are “primed” with drive system in the full
speed position.
9. Check hydro control linkage adjustment. Refer to
"Hydro Control Linkage Adjustment (Pistol Grip
Floating Deck)" on page 5 - 12.
By-Pass Valve (T-Bar)
The by-pass valve is adjustable to ensure easy
operation with a variety of deck sizes. If the front of the
deck lifts off the ground when the upper control bar is
quickly pushed forward or the machine is unable to
drive up hills, an adjustment may be needed.
Test Procedure
1. Start engine and run for 5 minutes at 3/4 throttle,
to warm hydraulic fluid.
2. Drive the machine to a clear and level open area
such as a driveway.
There should be at least 10 feet of clear
area in front of the machine.
3. Loosen the quick release levers and push the
reference bar forward to the “FAST” position. Lock
the quick release levers to secure the reference
bar.
4. Move throttle control to 3/4 throttle.
5. Quickly push the upper control bar against the
reference bar. The front caster wheels should
almost lift off the ground. If front caster wheels lift
the off the ground, the machine is too aggressive
and adjustment is required.
6. Move the engine throttle to the “FAST” position.
7. Quickly push the upper control bar against the
reference bar. The front caster wheels should lift
approximately 1 inch (25mm) off the ground. If
front caster wheels lift the off the ground more
than 2 inches (50mm), the machine is too
aggressive. Adjustment is required.
8. If the machine accelerates slowly, and the front
caster wheels do not lift off the ground, the
machine is too un-responsive. Adjustment is
required.
Adjustment Procedure
The by-pass valve should be adjusted to deliver best
performance for the size (weight) mower you have. The
by-pass valve factory setting is 1/2 turn out.
The following values can be used as initial settings for
different size mowers:
1. Loosen large jam nut several turns (Figure 77).
2. Gently close by-pass valve (Figure 77).
Do not over-tighten valve or needle and
seat may be damaged. Do not exceed 50 inch pounds
(6 N-m) to close valve.
3. Open by-pass valve 1/2 turn (Figure 77).
4. Tighten jam nut to lock the adjustment (Figure 77).
5. Repeat “Test Procedure” to check for proper
operation.
By-pass valve adjustment is very
sensitive, do not adjust more than 1/6 turn (one flat) at
a time.
Important
52 in. (132cm) 1/2 turn out
44 in. (112cm) 1 turn out
36 in. (91cm) 1-1/6 turn out
Important
Important