Ryobi 1090r, Operator'S Manual

Page: 23 / 28

MAINTENANCE AND REPAIR INSTRUCTIONS
23
Fig. 46
Fig. 47
7. Using a flat feeler gauge, measure the
clearance between the valve stems and
rocker arms (Fig 47).
The recommended clearance for both intake
and exhaust is
.003–.006 in. (0.076–0.0152 mm) .
The feeler gauge should slide between the
rocker arm and valve stem with a slight
amount of resistance, without binding.
8. If the clearance is not within specification,
adjust as follows:
a. Turn the adjusting nut using a 5/16 inch
(8 mm) wrench or nut driver (Fig. 47).
To increase the clearance, turn the
adjusting nut counterclockwise .
To decrease the clearance, turn the
adjusting nut clockwise .
b. Recheck both valve 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.Reinstall the engine cover. Check alignment
of the cover before tightening the screws.
Be sure to tighten the screws loosened
in step 1.
11.Check the spark plug, see Replacing the
Spark Plug , and reinstall. Torque the spark
plug to 100–110 in•lb (11.3–12.3 N•m) .
Reinstall the spark plug wire.
3. Disconnect the spark plug wire.
4. Remove the spark plug and then remove
the engine cover.
5. Remove the rocker arm cover and gasket
(Fig. 46).
6. While looking in the spark plug hole, pull the
starter rope slowly and bring the piston to
the top position. Check that both rocker
arms should move freely. If they do not,
repeat this step. This will be the top of the
compression stroke.
0.025 inch
(0.655 mm)
Fig. 48
REPLACING THE SPARK PLUG
Use a Champion RDZ19H spark plug
(or equivalent). Correct air gap is
0.025 in.
(0.655 mm) . Remove plug after every 50 hours
of operation and check its condition.
1. Stop the engine and allow it to cool. Pull the
wire off of the spark plug.
2. Clean around the spark plug and remove it
from the cylinder head. Use a 5/8 inch
socket to remove the plug.
CAUTION: Replace a cracked,
fouled or dirty spark plug. Do not
sand blast, scrape, or clean
electrodes because the engine
could be damaged by grit entering
the cylinder.
3. Set the air gap at 0.025 in. (0.655 mm)
using a wire feeler gauge (Fig. 48). Install
a correctly gapped spark plug into the
cylinder head. Torque to
100-110 in•lb
(11.3-12.3 N•m) .
Rocker Arm
Cover
Rocker Arm
Feeler
Gauge
Adjusting Nut
Gasket