MAINTENANCE AND REPAIR INSTRUCTIONS
16
service center.
NOTE:
Inspect the valve to rocker arm clearance with a feeler
gauge after the first 10 hours of operation and every
25 hours of operation.
• The engine must be cold when checking or adjusting the
valve clearance.
• This task should be performed inside, in a clean, dust free
area.
1.
Remove the six (6) screws on the back of the engine cover
with a Flat-head or T-25 Torx screwdriver (Fig. 49).
2.
Disconnect the spark plug wire.
3.
Clean dirt from around the spark plug. Remove the spark
plug from the cylinder head by turning a 5/8 in. socket
counterclockwise.
4.
Remove the engine cover (Fig. 49).
5.
Clean dirt from around the
rocker arm cover. Remove
the screw holding the rocker
arm cover with a large flat
blade screwdriver or Torx T-
25 bit (Fig. 50). Remove the
rocker arm cover and gasket.
6.
Pull the starter rope slowly to
bring the piston to the top of
its travel, (known as top dead
center). Check that:
• The piston is at the top of
its travel while looking in
the spark plug hole (Fig. 50)
• Both rocker arms move
freely, and both valves are
closed
If these statements are not true, repeat this step.
7.
Slide the feeler gauge between the rocker arm and the
valve return spring. Measure the clearance between the
valve stem and rocker arm (Fig. 51). Measure both the
intake and exhaust valves.
The recommended clearance for both intake and exhaust is
.003 – .006 in. (.076 – 0.152 mm). Use a standard automotive
.005 in. (0.127 mm) feeler gauge. The feeler gauge should slide
between the rocker arm and valve stem with a slight amount of
resistance, without binding. See Figures 51 and 52.
8.
If the clearance is not within specification:
a. Turn the adjusting nut using a 5/16 inch (8 mm) wrench or
nut driver (Fig. 52).
• To increase clearance, turn the adjusting nut
counterclockwise.
• To decrease clearance, turn the adjusting nut clockwise.
b. Recheck both clearances, and adjust as necessary.
Remove
Screws
View Of The Rear Engine Cover
Remove
Screws
Rocker
Arm
Cover
Spark
Plug
Hole
9.
Reinstall the rocker arm cover using a new gasket. Torque
the screw to 20–30 in•lb (2.2–3.4 N•m).
10. Check the spark plug and reinstall. See
Replacing the
Spark Plug
.
11. Replace the spark plug wire.
12. Reinstall the engine cover. Check alignment of the cover
before tightening the screws. Tighten screws.
REPLACING THE SPARK PLUG
Use a replacement part number 753-05255 spark plug. The
correct air gap is 0.025 in. (0.635 mm.). Remove the plug after
every 25 hours of operation and check its condition.
1.
Stop the engine and allow it to cool. Remove the six (6)
screws on the back of the engine cover with a Flat-head
or T-25 Torx screwdriver (Fig. 49).
2.
Grasp the plug wire firmly and pull the cap from the spark
plug.
3.
Clean dirt from around the spark plug. Remove the spark
plug from the cylinder head by turning a 5/8 in. socket
counterclockwise.
Adjusting Nuts
Feeler Gauge
Rocker Arms
INTAKE
EXHAUST
Spark Plug
Hole
Feeler Gauge
Adjusting Nut
Rocker Arm
.003–.006 in.
(.076–.152 mm)
Valve Stem
WARNING:
Do not sand blast, scrape or clean
electrodes. Grit in the engine could damage the
cylinder.
Fig. 51
Fig. 50
Fig. 49
Fig. 52
Summary of Contents for TB525ET
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