Replacing The Spark Plug; Carburetor Adjustment - Bolens BL150 Operator's Manual

MAINTENANCE & REPAIR INSTRUCTIONS

CARBURETOR ADJUSTMENT

The idle speed of the engine is adjustable through the air
filter/muffler cover (Fig. 26).
NOTE: Careless adjustments can seriously damage
your unit. An authorized service dealer should
make carburetor adjustments.
Check Fuel Mixture
Old and/or improperly mixed fuel is usually the reason for
improper unit performance. Drain and refill the tank with
fresh, properly-mixed fuel prior to making any adjustments.
Refer to Oil and Fuel Information.
Clean Air Filter
The condition of the air filter is important to the operation of
the unit. A dirty air filter will restrict air flow and change the
air/fuel mixture. This is often mistaken for an out of
adjustment carburetor. Check the condition of the air filter
before adjusting the idle speed screw. Refer to Air Filter
Maintenance.
Adjust Idle Speed Screw
If, after checking the fuel mixture and cleaning the air filter,
the engine still will not idle, adjust the idle speed screw as
follows:
WARNING: The cutting attachment may be
spinning during idle speed adjustments. Wear
protective clothing and observe all safety
instructions to prevent serious personal injury.
1. Start the engine and let it run at a high idle for a minute
to warm up. Refer to Starting/Stopping Instructions.
2. Release the throttle trigger and let the engine idle. If the
engine stops, insert a small phillips or flat blade
screwdriver into the hole in the air filter/muffler cover
(Fig. 26). Turn the idle speed screw in, clockwise, 1/8 of a
turn at a time (as needed) until the engine idles smoothly.
Fig. 26
Idle Speed Screw
3. If the engine appears to be idling too fast, turn the idle
speed screw counterclockwise 1/8 of a turn at a time (as
needed), to reduce idle speed.
Checking the fuel mixture, cleaning the air filter, and
adjusting the idle speed should solve most engine problems.
If not and:
• the engine will not idle
• the engine hesitates or stalls on acceleration
• there is a loss of engine power
Have the carburetor adjusted by an authorized service dealer.
WARNING: To prevent serious personal injury,
make sure the cutting attachment has stopped
rotating before you turn it off and set it down.

REPLACING THE SPARK PLUG

Use a Champion RDJ7Y spark plug, or equivalent. The correct air
gap is 0.020 inch (0.5 mm). Remove the plug after every 25
hours of operation and check its condition.
1. Stop the engine and allow it to cool. Grasp the plug wire
firmly and pull it from the spark plug.
2. Clean around the spark plug. Remove the spark plug
from the cylinder head by turning a 5/8-inch socket
counterclockwise.
3. Replace a cracked, fouled or dirty spark plug. Set the air
gap at 0.020 in. (0.5 mm) using a feeler gauge (Fig. 27).
CAUTION: Do not sand blast, scrape or clean
electrodes. Grit in the engine could damage the
cylinder.
4. Install a correctly-gapped spark plug in the cylinder
head. Tighten by turning the 5/8-inch socket clockwise
until snug.
If using a torque wrench torque to:
110-120 in.•lb. (12.3-13.5 N•m)
Do not over tighten.
0.020 in.
(0.5 mm)
15
Fig. 27