Cub Cadet SC 621 Operator's Manual page 15

Blade
Adapter
Figure 17
WARNING: Periodically inspect the blade
adapter for cracks, especially if you strike
a foreign object. Replace when necessary.
When sharpening the blade, follow the original angle of
grind as a guide. It is extremely important that each
cutting edge receives an equal amount of grinding to
prevent an unbalanced blade. An unbalanced blade will
cause excessive vibration when rotating at high
speeds. It may cause damage to the mower, and could
break causing personal injury.
The blade can be tested by balancing it on a round
shaft screwdriver. Remove metal from the heavy side
until it balances evenly. It is recommended that the
blade always be removed from the adapter when
testing for balance. Before installing the blade and the
blade adapter to the unit, lubricate the engine
crankshaft and the inner surface of the blade adapter
with light oil.
• Be sure to install the blade with the side of the
blade marked "Bottom" (or with part number) facing
the ground when the mower is in the operating
position.
• Slide the blade adapter onto the engine crankshaft.
• Place the blade on the adapter. Be certain the
blade is aligned and seated on the blade adapter
flanges.
• Place blade bell support on blade. Make sure the
notches on the blade bell support are aligned with
small holes in the blade.
• Replace hex bolt and tighten hex bolt to torque: 450
in. lbs. min., 600 in. lbs. max.
NOTE: To ensure safe operation of your mower, the
blade bolt must be checked periodically for correct
torque.
Drive Belt Removal and Replacement
• Disconnect the spark plug wire and ground it
against the engine.
• Drain the fuel tank or place a piece of plastic
beneath the cap to prevent gasoline leakage.
• Place shift lever in the first position and tip the
mower on its side.
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Blade Bell
Support
Hex Bolt
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15
Remove the center bolt which secures the blade to
the crankshaft followed by blade bell support,
blade, and blade adapter.
Move the cutting height adjustment to the highest
position.
Remove the three hex screws holding the baffle to
the deck and pivot baffle towards the rear of the
mower. See Figure 18.
Figure 18
Remove the hex bolt from the rear of unit holding
the transmission to the mower housing.
See Figure 19.
Cutting Height
Adjustment
Figure 19
Tilt the transmission forward and loosen the idler
pulley bolt and lock nut half a turn. See Figure 20.
Using a pair of pliers, pull back and rotate belt
keeper bracket from the slot on the idler pulley.
Slide the belt out from between the belt keeper
bracket and the idler pulley.
Squeeze the belt together and push it forward,
while pressing the control arm inward towards the
deck and remove the six speed cable from the slot.
See Figure 20.
Pivot the control arm down away from the pulley
and belt.
Lift off the lower pulley assembly and remove the
old belt from around the crankshaft. See Figure 20.
Place the new belt over the transmission pulley.
Start the belt in the pulley groove and rotate the
pulley until the belt is seated in the transmission
pulley.
Baffle
Hex Bolt