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Workshop manual
3.4 Muffler
Long use of the muffler can cause carbon deposit, which will
severely affect the exhaust system; in order to let exhaust system
work more reliably, we normally need to remove the carbon deposit
from the muffler.
Use a hand hammer to gently knock the muffler, and blow it with
compressed air to remove the carbon deposit inside it.
If the muffler has water drops in it, and severe erosion, which cause
higher exhaust noise, replace it with a new one.
Never use wires to clean, or the acoustic absorbent will be scraped
off, and acoustic absorbing performance will be worse.
Never reuse the muffler gasket.
3.5 Spark plug
Recommended type: F7RTC or a spark plug of an equivalent
grade. Replacing the spark plug has the following positive effect:
ensuring continuous production of sparks, more reliable starting.
Caution
Spark plugs of a wrong model or incorrect heat range can
cause engine damage.
1. Remove the spark plug cap, and remove the dirt from around
the spark plug.
2. Remove the spark plug with a spark plug wrench.
3. Inspect the spark plug for excessively worn electrodes, chips or
cracks in the insulator, or excessive deposits. Replace the spark
plug if you have any doubts about its condition.
4. Measure the electrode gap with a gap gauge; the correct gap is
0.7 ~ 0.8 mm; if the gap need be adjusted, slightly knock (when
the gap is to big), or slightly pry the electrode with a slot type
screwdriver (when the gap is too small).
5. Use a spark plug wrench to tighten the spark plug enough to let
it press on the washer. If reinstalling a used spark plug, tighten
1/8 to 1/4 of a turn after the spark plug presses on the washer.
If installing a new spark plug, tighten 1/2 turn after the spark
plug presses on the washer.
Caution
A loosely installed spark plug can become hot enough to
damage the engine. Over tightening a spark plug can
damage the threads in the engine.
6. Install the spark plug cap on the spark plug.
0.7-0.8 mm
19
Spark plug
wrench
Side electrode
Wire brush
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