Kohler K91 Owner's Manual page 258

TROUBLE SHOOTING GUIDE
This
trouble shooting guide is designed to help
determine
if
a Hydrogear can be repaired within the
limits of authorized service procedures or
if
the
assembly must be replaced.
First, listen carefully to the operator's description of
the problem. Then operate the tractor to confirm
the condition. Hydrogear transmission malfunctions
usually show up in one of the following ways:
1.
2.
3.
4.
5.
Tractor
will
not operate in either direction
includes conditions ranging from completely
inoperative to lack or loss of power in both
directions.
Tractor operates in one direction only much
the same a s item 1, except that
it
applies
to one direction only.
Erratic engagement sharp, jerky, or abrupt
acceleration and braking in one or both direc-
tions.
Transmission overheats likely to accompany
one of the other conditions listed. Normal
temperature 180 degrees
F.
Transmission noisy noise may issue from
either the Hydrogear or the transaxle.
PRELIMINARY CHECKS
Make it a practice in every case to perform the
following preliminary checks. They will pinpoint some
easily overlooked items and save the time and ex-
pense involved with unnecessary teardown.
1.
2.
3 .
4.
5.
6.
7.
Check oil level in reservoir and replenish
if
necessary.
Check control linkage to make sure
it
i s prop-
erly connected and operates normally.
Close towing valve and try to push the tractor.
If
the tractor can be pushed, a malfunctioning
valve i s usually indicated.
Make sure the tractor can be pushed with the
towing valve open.
If
it cannot be pushed,
there may be a valve malfunction, seized gear
motor, or transaxle failure.
Check drive belt condition and fit. Make sure
parking brake operation is normal.
Check for oil leakage at operating shafts,
gasketed joints, filter base, etc. Replace gaskets
and seals as necessary.
Check and correct air cooling fins clogged with
dirt or clippings, or other apparent damage or
trouble causing condition.
The trouble shooting chart indicates possible causes
and test or corrective procedures for the five trouble
conditions listed above. The Hydrogear Tune-up pro-
cedures are recommended as a correction in several
cases.
HYDROGEAR TUNE-UP
CAUTION:
Cleanliness i s one of the most important
considerations during every step of the Hydrogear
tune-up. Instead of repeating a cleanliness precaution
throughout these instructions, this note at the begin-
ning is intended to emphasize its importance. Exer-
cise the utmost care at all times to prevent the intro-
duction of dirt, clippings or any other foreign matter
into the hydraulic system.
Remove the fender and tool box assembly to expose
the center section of the Hydrogear as shown in
Fig.
90.
Thoroughly clean the center section of all dirt,
clippings, etc.
with
a solvent that i s not harmful to
paint. Remove the drain plug at the bottom of the
transaxle cape and drain the fluid. Remove the oil
filter for replacement.
FIG. 90.
Prepare a clean work area for inspecting the highly
polished surfaces of the valves to be serviced. The
parts to be removed are manufactured to close
tolerances and are very critical to the proper opera-
tion of the Hydrogear. Handle them with care to
avoid damage to the sealing surfaces.
Acceleration Relief Valves: Remove the forward
dampening valve (item
2,
Fig.
90)
with a
1 3/16"
wrench
on the hex head. Occasionally the acceleration valve
piston and sleeve assembly
(2 8 3,
Fig.
91)
remains
on the dampening valve when removed. When this
happens, separate them for inspection and cleaning.
If
the piston and sleeve remained in the bore, re-
move the piston,
(2,
Fig.
91)
two springs
(4 & 5, Fig.
91),
spring seat
(6,
Fig.
91),
and relief valve cone
(7, Fig. 91),
using a small magnet to withdraw them
from the bore.
The acceleration valve sleeve
(3,
Fig.
91),
and relief
valve seat (8, Fig.
91)
may now be removed.
This
i s
best accomplished by inserting a stiff wire hook into
the drain port in the side of the seat and pulling,
(See Figs.
91,
Fig.
11).
The force necessary will de-
pend on the radial press of the sealing
"0"
rings on
the sleeve and seat.
49