Kohler K91 Owner's Manual page 259

FIG. 91.
HYDROGEAR SERVICE NOTE
PROBLEM:
Tractor
will
not operate in either direction.
Problem usually occurs suddenly, with little or no
warning.
CAUSE:
Internal plug (b) i s either loose, or has fallen
completely out of position.
1. Remove the side socket head plug (c) using
a
3/16"
Allen wrench.
2.
Insert the long arm of
a
Allen wrench into
the horizontal passage exposed in Step
1,
across the large vertical passage, and deter-
mine
if
the internal plug i s in place.
3. If
the internal plug i s in place but i s loose,
tighten
it
securely and replace the side plug.
4. If
the internal plug i s not i n place, use a
7/16"
Allen wrench to remove the top plug
(a).
The
internal plug i s usually found at the bottom of
the large vertical passage. Retrieve
it
with a
magnet.
5.
Insert the internal plug through the horizontal
passage, across the large vertical passage, and
tighten
it
securely in place. Then reinstall both
the side and top plugs.
FIGURE II SOLUTION: