Kohler K91 Owner's Manual page 260

FIG.
92.
NOTE: A
large amount of iron or brass filings on
the valves and the .passages usually indicates internal
damage to the pump or motor section of the Hydro-
gear.
This
is also true
if
there is evidence of severe
contamination from an outside source. Because com-
plete disassembly would
be
necessary to repair such
damage or to clean out the contaminate, replacement
of the complete Hydrogear assembly is advised.
Moderate contamination can be flushed out through
the valve ports with solvent.
The most critical area of the acceleration relief
valve is the dampening valve portion
(1,
Fig. 91).
Remove the
" 0 "
rings and discard them. Clean the
valve thoroughly with solvent, and inspect for visual
damage.
If
there are indications of damage to the
pin or ball, or
if
the valve rattles when shaken, re-
place the dampening valve assembly.
Inspect the relief valve cone
(7,
Fig. 91) and mating
seat
(8,
Fig. 91) for damage.
Check
the cone for
uniformity of sealing pattern. Normal cones will
show a shiny unbroken circle of contact approxi-
mately
5/32"
from the point. Similarly, the mating seat
should be free of nicks or signs of erosion.
If
the
pattern is broken or the seat damaged, the cone
and seat should
be
replaced. Remove
"0"
ring from
the seat and discard. Clean the parts thoroughly with
solvent and let them air dry.
Next examine the acceleration valve sleeve
(3,
Fig. 91) and piston
(2,
Fig. 91) for scoring or sticky
operation.
If
either part i s severely scored, both must
be
replaced. They are serviced as a matched set.
Sticky piston operation can be corrected by lightly
polishing the piston and bore of the sleeve with
Crocus cloth.
The
piston-to-bore clearance is extremely
close; therefore, the piston may not pass through the
sleeve under its own weight. Remove the
"0"
rings
from the sleeve and discard them. Wash piston and
sleeve with solvent and air dry them.
Inspect the springs
(4 & 5,
Fig. 91) and spring seat
(6) for damage and replace
if
necessary. Clean with
solvent and dry.
Check
Valves (Forward and Reverse)
Remove the reverse check valve
" 0 )
ring plug
(4,
Fig. 90) with a wrench on the hex head. Remove
the spring
(9,
Fig. 91) and valve (10, Fig. 91) using a
magnet or long nose pliers
if
needed. Check the
spring for distortion. Replace it
if
damaged. Remove
and discard the
" 0
ring from the plug.
Check
the cone for uniformity of sealing pattern.
A
normal cone will have a shiny unbroken circle of
contact approximately
5/32"
from the point. The seat
inside the center section should also be free of nicks
or signs of erosion.
If
the contact pattern
i s
broken,
the cone should be replaced.
If
the seat
i s
badly
eroded, the' Hydrogear assembly must
be
replaced.
Clean the parts in solvent and coat them with
type
"A"
automatic transmission fluid. Install a new
"0"
ring
on
the plug
(4,
Fig. 90) using care not to
damage the' ring on the screw threads. Slip the spring
over the shoulder of the valve and install the assem-
bly into its bore i n the center section. Install the hex
head
"0"
ring plug and tighten securely.
Repeat this operation on the forward check valve
assembly
(3,
Fig. 90).
51