Testing Cylinder Compression; Cleaning Cooling Air Passages - Echo PB-251 Service Manual

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7-1 Testing cylinder compression

7-2 Cleaning cooling air passages

(A)
ENGINE
NOTE: Test cylinder compression when engine is
cold.
1. Set ignition switch to STOP position and remove
spark plug.
2. Install compression gauge in cylinder spark plug
hole as shown and pull starter several times to sta-
bilize reading.
3. If pressure is lower than approx. 90psi, check cyl-
inder bore, piston and piston ring if worn-out. (Refer
to "1-2 Technical data" for standard compression
pressure.)
4. If pressure is more than approx. 145psi, check
cylinder combustion chamber and exhaust port, pis-
ton crown, and muffler for carbon deposits.
NOTE: Compression pressure varies with volume
of compression gauge tip occupying cylinder com-
bustion chamber. If gauge tip volume is considerably
different from spark plug volume, it is recommended
to measure and note compression pressures of
brand-new engines as standard pressure in ad-
vance.
5. Remove compression gauge, then install spark
plug and spark plug cap.
NOTE: Blocked pawl carrier fins (A), cylinder cool-
ing fins or air intake will cause engine overheat and
seizure.
1. Remove muffler cover and starter case.
2. Inspect pawl carrier fins (A). If blocked with leaves
or other debris, clean as required.
PB-251