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ENGINE
CS-370ES
CS-420ES
7-1 Testing cylinder compression
NOTE: Test cylinder compression when engine is
cold.
1. Move ignition switch to STOP position. Then
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.
4. If pressure is more than approx. 125% of standard compression pressure, inspect cylinder combustion
chamber and exhaust port, piston crown, and muffler for carbon deposits.
NOTE: Compression pressure varies with volume of compression gauge tip occupying cylinder combustion
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 passage
1. Remove cylinder cover and starter assembly from
the unit.
WARNING DANGER
Always wear eye protection when using com-
pressed air for cleaning. Otherwise, eye
damage can occur from flying particles
2. Inspect cylinder cooling fins (A) for blockage with
dirt and/or saw dust. Clean them with wooden or
plastic stick or compressed air as required.
3. Install all removed parts.
A
A
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