Yard-Man 979 Operator's Manual page 14

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 reinstalling 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 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 with air filter facing up.
• 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 17.
Figure 17
• Remove the hex bolt from the rear of unit holding
the transmission to the mower housing.
See Figure 18.
Cutting Height
Adjustment
• Tilt the transmission forward and loosen the idler
pulley bolt and lock nut half a turn. See Figure 19.
• 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.
Transmission
Pulley
Belt
Belt Keeper
Bracket
Idler Pulley
Bracket
Idler Pulley
Bolt and
Locknut
• 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
Baffle
and belt.
• Lift off the lower pulley assembly and remove the
old belt from around the crankshaft. See Figure 20.
14
Hex Bolt
Figure 18
Transmission
Figure 19