Ryobi 990r - Manual (Page 22)

22
Inspection and Cleaning
Inspect the inlet port of the muffler and outlet port of the
cylinder for excessive carbon build-up. Excessive deposits
around the exhaust ports or exhaust holes will cause poor
engine performance.
If carbon build-up cannot be cleaned, replace the muffler.
Inspect the muffler mounting holes for elongation. Replace
the muffler if the holes are elongated.
MAINTENANCE AND REPAIR INSTRUCTIONS (Continued)
Muffler Reassembly
1. Install a new muffler gasket and place the muffler
baffle in place (Fig. 45).
2. Install the muffler with the three (3) mounting bolts.
Install the lower bolt first to ease the installation of the
top two (2) bolts (Fig. 46).
NOTE: The 5 mm nut must be held in the slot
next to the spark plug before installing
the top rear muffler bolt.
NOTE: Be careful not to crossthread the muffler
mounting bolts.
Torque the muffler mounting bolts to 40-45 in•lb
(4.5-5.0 N•m).
Checking Spark Arrester Screen
This unit is equipped with a spark arrester screen. Every
50 hours of operation, check the spark arrester screen
for debris and / or deposits.
WARNING
Make sure the muffler is cool before checking
the spark arrester screen to prevent injury.
Check the spark arrester screen as follows:
1. Remove the screw (Fig. 44).
2. Remove the cover (Fig. 44).
3. Push the spark arrester screen out of the cover.
Fig. 44
Cover
Screw
Spark Arrester
Screen
4. Inspect the spark arrester screen.
If the screen is clean, reinstall the screen, cover and
screw. If the screen is plugged, replace it.
5. Torque the screw to 15-20 in•lb (1.7-2.2 N•m).
Fig. 45
Fig. 46
Muffler Mounting
Bolt
Muffler Mounting
Bolt
Muffler
Muffler Gasket