Troy-Bilt Horse TB525CS Operator's Manual page 14

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. 45). 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 45 and 46.
Adjusting Nut
.003–.006 in.
(.076–.152 mm)
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. 45).
• To increase clearance, turn the adjusting nut
counterclockwise.
• To decrease clearance, turn the adjusting nut
clockwise.
b. Recheck both clearances, and adjust as necessary.
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.
MAINTENANCE AND REPAIR INSTRUCTIONS
Rocker Arm
Feeler Gauge
Valve Stem
Fig. 46
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. 43).
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.
4. Replace cracked, fouled or
dirty spark plug. Set the air
gap at 0.025 in. (0.635 mm.)
using a feeler gauge (Fig. 47).
5. Install a correctly-gapped
spark plug in the cylinder
head. Turn the 5/8 in.
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.
WARNING:
electrodes. Grit in the engine could damage the
cylinder.
14
0.025 in.
(0.635 mm.)
Fig. 47
Do not sand blast, scrape or clean