Adjusting Carburetor - Toro 521 Operator's Manual

1. Pull wire off spark plug and make sure wire does
not contact plug accidentally.
2. Remove (4) screws securing bottom cover to
frame. Remove cover (Fig. 21).
3. Loosen flange nuts securing selector plate to
control panel. This allows selector plate to move
freely for adjustment (Fig. 28).
4. Shift speed selector to third gear and push down
on speed selector plate to move drive assembly
to the right. Drive assembly should be / " from
roll pin; if not, slide selector plate (Fig. 28) until
/ " dimension is correct (Fig. 29).
5. With drive assembly / " from contacting roll
pin, tighten flange nuts securing speed selector
plate.
6. Shift speed selector to R (REVERSE) and back
to third to check adjustment. If space between
roll pin and drive assembly is more than /
an inch (4.8 mm), repeat steps 2–4.
7. Reassemble bottom cover with (4) screws.

Adjusting Carburetor

The carburetor has been adjusted at the factory, but an
occasional adjustment may be required.
1. Remove carburetor heater box: see To Start
Engine, paragraph one, steps A & B, page 11.
Note: Skip steps 2 and 3 if the engine will start and
run.
2. Power Adjusting Screw (Fig. 30)—Close screw
by gently rotating it clockwise until a slight
seating resistance is felt. Next, rotate power
adjusting screw one full
turn—360 —counterclockwise.
IMPORTANT: Do not close power adjusting
screw or idle mixture screw too tight because
the screw and seat will likely be damaged.
3. Idle Mixture Screw (Fig. 30)—Close screw by
gently rotating it clockwise until a slight seating
resistance is felt. Next, rotate idle mixture screw
1–1/2 full turns counterclockwise.
4. Start engine and let it warm up for
approximately 3 to 5 minutes; then move throttle
to FAST.
POTENTIAL HAZARD
Engine must be running so final adjustment of
the carburetor can be performed.
WHAT CAN HAPPEN
Personal injury is possible.
HOW TO AVOID THE HAZARD
Move auger drive and traction drive controls to
DISENGAGE.
Remember to keep hands, feet, face, and other
of
parts of your body or clothing away from
muffler, auger, discharge chute, and any
moving part(s).
POTENTIAL HAZARD
Engine exhaust contains carbon monoxide.
WHAT CAN HAPPEN
Carbon monoxide is an odorless, deadly
poison.
HOW TO AVOID THE HAZARD
Do not run engine indoors or in an enclosed
area.
5. Rotate power adjusting screw (Fig. 30)
clockwise—in—1/8 turn at a time until engine
misses because of a lean gasoline mixture. Then
rotate screw counterclockwise—out—1/8 turn at
time until engine runs unevenly because of a rich
gasoline mixture. Next, rotate power adjusting
screw clockwise, back to the midpoint between
the rich and lean settings, so engine runs
smoothly.
17