Testing Cylinder Compression; Cleaning Cooling Air Passages - Yamabiko ECHO PB-2520 Service Manual

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7-1 Testing cylinder compression

A
4. If pressure is more than approx. 125% of standard compression pressure, inspect cylinder combustion
chamber and exhaust port, piston crown, and muf er for carbon deposits.
NOTE: Compression pressure varies with volume of compression gauge tip occupying cylinder combus-
tion chamber. If gauge tip volume is considerably different from spark plug volume, it is recommended to
measure and note compression pressure of brand-new engines as standard pressure in advance.

7-2 Cleaning cooling air passages

A
ENGINE
B
C
NOTE: Test cylinder compression when engine is
cold.
1. Set ignition switch to STOP position and remove
spark plug.
2. Install compression gauge 91037 (A) in spark
plug hole and tighten by hand. Pull starter several
times to stabilize reading on compression gauge.
3. If pressure is lower than approx. 75% of
standard compression pressure (Refer to "1-2
Technical data"), inspect cylinder bore, piston and
piston ring for wear or damage.
NOTE: To maintain proper engine operating tem-
peratures, cooling air must pass freely through the
cylinder n area. This ow of air carries combus-
tion heat away from the engine.
1. Clean accumulated debris from crankcase in-
take grill (A) and discharge grill (B) with brush or
compressed air as required.
WARNING
Always wear eye protection when using
compressed air for cleaning. Otherwise,
eye damage can occur from fl ying particles.
2. Remove engine cover if cylinder fins (C) are
hard to clean. Clean the clearance of cylinder ns
using wooden stick, plastic stick or compressed
air.
NOTE: To prevent debris from entering cylinder,
reinstall spark plug, carburetor, and air lter before
cleaning cylinder ns.
PB-2520
EB252
DANGER