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7-4. CARBURETOR ADJUSTMENT
The carburetor was pre-set at the factory for optimum per-
formance. The only adjustment should be to idle speed see
section 5-4, Idling/Carburetor adjustment.
7-5. SPARK PLUG
1. To remove spark plug B (figure 7-6A) for cleaning or
replacement: make sure engine is off, spark plug is cool
then grasp spark plug boot firmly and remove from
spark plug. Remove spark plug with correct spark plug
tool. Inspect, clean or replace as needed.
2. Spark plug gap = .025" (.635mm) (Figure 7-5A).
3. Torque to 105 to 130 inch pounds (12 to 15 N•m).
Connect spark plug boot.
4.
If necessary, replace with Champion RZ7C or equiva-
lent.
7-6. SPARK ARRESTER SCREEN
1. To replace spark arrester screen (A) (Figure 7-6A), use
a needle nose pliers, pinch an edge of the spark
arrester screen. Pull the whole spark arrester screen
out.
2.
Use the needle nose pliers to push in a ne
w spar
k
arrester screen.Then open the pliers a little to press the
inner surf
ace of the spar
k arrester screen to fasten it.
7-7. DEBRIS SHIELD KNIFE SHARPENING
1. Remove cutter knife (A) from debris shield (B) (Figure
7-7A).
2. Place knife in a bench vise. Sharpen knife using a flat
file, being careful to maintain the angle of cutting edge.
File in one direction only.
7-8. STORING A UNIT
Failure to follow these steps may cause varnish to
form in the carburetor and difficult starting or perma-
nent damage following storage.
1. Perform all the general maintenance recommended in
the Maintenance Section of your User Manual.
2. Clean exterior of engine, drive shaft assembly, debris
shield and stringhead.
3. Drain fuel from the fuel tank.
4. After fuel is drained, start engine.
5. Run engine at idle until unit stops. This will purge the
carburetor of fuel.
6. Allow engine to cool (approx. 5 minutes).
7. Using a spark plug wrench, remove the spark plug.
8. Pour 1 teaspoon of clean 2-cycle oil into the
combustion chamber. Pull starter rope slowly several
times to coat internal components. Replace spark plug.
9. Store unit in a cool, dry place away from any source of
ignition such as an oil burner, water heater, etc.
7-9. REMOVING A UNIT FROM STORAGE
1. Remove spark plug.
2.
Pull star
ter rope briskly to clear excess oil from com-
b
ustion chamber
.
3. Clean and gap spark plug or install a new spark plug
with proper gap
.
4.
Prepare unit f
or oper
ation.
5. Fill fuel tank with proper fuel / oil mixture. See Fuel and
Lubr
ication Section.
16 17
7 - MAINTENANCE INSTRUCTIONS 8 - TROUBLESHOOTING THE ENGINE
7-5A
.025" (.635mm)
7-6A
A
B
7-7A
B
A
PROBLEM PROBABLE CAUSE CORRECTIVE ACTION
Unit won’t start or starts but will not run.
Incorrect starting procedures. Follow instructions in the User Manual.
Incorrect carburetor mixture adjustment
setting.
Have carburetor adjusted by an
McCulloch Authorized Service Center.
F
ouled spark plug
Clean / gap or replace plug.
Fuel filter plugged. Replace fuel filter.
Unit starts, but engine has low power.
Incorrect lever position on choke. Move to RUN position.
Dirty spark arrester screen. Replace spark arrester screen.
Dirty air filter. Remove, clean and reinstall filter.
Incorrect carburetor mixture adjustment
setting.
Have carburetor adjusted by an
McCulloch Authorized Service Center.
Engine hesitates.
Incorrect carburetor mixture adjustment
setting.
Have carburetor adjusted by an
McCulloch Authorized Service Center.
No power under load.
Runs err
atically.
Incorrectly gapped spar
k plug.
Clean / gap or replace plug.
Smokes excessively.
Incorrect carburetor mixture adjustment
setting.
Have carburetor adjusted by an
McCulloch Authorized Service Center.
Incorrect fuel mixture Use properly mixed fuel (40:1 mixture).