Exmark metro 21 Operator's Manual page 20

NOTE: You can vary the ground speed by increasing or decreasing the
distance between the ground speed control and the handle. Lower the control
bar to decrease the ground speed when you are making a turn or if the lawn
mower is moving too fast for you. If you lower the control bar too far the lawn
mower stops self-propelling. Squeeze the ground speed control closer to the
handle to increase the ground speed. When you hold the ground speed
control tight against the handle, the lawn mower self-propels at the maximum
ground speed. Move the ground speed control to the Neutral position when
you use the lawn mower for trimming or whenever you leave the lawn mower.
3.3.5 Operating the Blade Control Lever (Blade Brake Clutch Units Only):
1. Start the engine.
2. Squeeze the blade control bail against the handle (Fig. 1).
3. Move the blade control lever to the full forward Latch position. Blades should
engage.
4. Release the blade control bail to disengage the blades.
NOTE: The blade control lever will release rapidly when the blade control bail
is released. To avoid minor injury, keep hands clear of the blade control lever
when the blade control bail is released.
3.3.6 Using the Discharge Tunnel:
1. Stop the engine and wait for all moving parts to stop.
2. Insert the plug. (Refer to Section 3.4 Installing the Discharge Plug).
3. To remove the plug, move the discharge door handle rearward and lift up the
spring clip on the bottom of the plug. When the plug is unlocked, pull it out of
the discharge tunnel.
NOTE: When grass is thick and lush, clippings may collect on and around the
discharge tunnel plug. This may make removing the plug difficult. Clean the
plug thoroughly after each use.
3.3.7 Checking the Blade Brake Clutch (Blade Brake Clutch Units Only):
Check the Blade Brake Clutch (BBC) system before each use to ensure that it is
operating properly.
Normal Test:
1. Stop the engine and wait for all moving parts to stop.
2. Move the lawn mower onto a paved surface in a non-windy area.
3. Set all four wheels in to the 2-1/2 in. (64 mm) cutting height (Fig 8).
4. Set the ground speed selector to the N (Neutral) position .
5. Take a half sheet of newspaper and crumple it into ball small enough to go under
the deck (about three inches or 76 mm in diameter) as shown in Figure 7.
6. Place the ball of newspaper five inches (12.7 cm) in front of the lawn mower
(Fig. 8).
G1112
Figure 8
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5 in (12.7 cm)