Walker MC (20 HP) - Manual (Page 72)

68
Maintenance Instructions
REPLACING/REPAIRING
PTO Shear Pin
The PTO drive shaft connection to the deck gearbox
has a shear pin to provide shock load protection to
the mower deck drive. This system provides pri-
mary shock protection in case of blade impact and
will normally shear before the individual shear bolts
on the blade hub.
When the PTO pin has sheared, use the following
procedure to replace it:
1. Loosen the two bolts securing the PTO shaft
guard on the deck; lift the guard off. (Holes in
guard are slotted for easy removal.)
2. Rotate U-joint on shaft to align the shear pin
hole with the hole (and shear pin fragment) in
the shaft. Use a punch to drive the remaining
portion of the old shear pin out.
3. Install new shear pin and secure with cotter pin.
U-Joint
Shaft Assembly
U-Joint
Tube Assembly
Cotter Pin
Shear Pin
Split Spring Pin
(Retains U-Joint Held on Shaft
with Broken Shear Pin)
PTO Shear Pin
IMPORTANT: Use only Walker P/N 8067-13
shear pins for replacement to provide proper
shock protection -- these pins are hardened to
shear under a specific amount of load.
4. Reinstall the PTO shaft guard.
Before operating the deck, inspect the blade over-
load shear bolts and also check blade timing (on
gear driven decks) by moving blades through one
(1) complete revolution. Make sure blade tips
pass clear of each other. If timing is incorrect, con-
tact your Walker dealer.
NOTE: Use Walker P/N 8067-10 for heavy duty
gearboxes.
Mower Blades
Mower blades are removed and remounted as de-
scribed in Sharpen Mower Blades instructions.
During the course of sharpening and inspecting
mower blades, if there are any of the following
conditions of wear or damage, blades should be
replaced for reasons of safety and performance of
the machine:
• An excessive amount of the flat section of the
blade has been ground away (removed) when the
blade is sharpened. Replace the blade when less
than a 3/4 in. (19 mm) flat section remains at the
blade tip.
• Examine ends of the blade carefully, especially
the intersection where the flat section of the blade
turns up to form the “wing tip” (refer to Mower Blade
Profile for Sharpening illustration in Sharpen
Mower Blades instructions). Since sand and abra-
sive material can wear metal away in this area, the
blade should be replaced when metal thickness
has worn to 1/16 in. (1.6 mm) or less.
DANGER
When blades are operated over sandy
soil, and if blades are allowed to wear, a
“slot” may be worn into the wing tip of
blade. Eventually a piece of the blade
may break off creating a serious potential
for injury or damage.
• Check the blades for straightness by marking
blade tip position inside the deck housing and then
rotating the opposite end of the blade to the same
position and comparing. If the difference in blade tip
track is more than 1/8 in. (3 mm), the blade is bent
and should be replaced.
• Inspect the blade surface, especially in formed
areas, for cracks. Replace the blade if any cracks
are found.
WARNING
DO NOT try to straighten a blade that is
bent. NEVER weld a broken or cracked
blade. ALWAYS replace with a new blade
to assure safety.