42
2-15 CYLINDER PRESSURE
Note:
(1) Check the cylinder pressure at warm engine
condition.
(2) Use compressed air to blow away deposits
around spark plug before removing spark
plug. Otherwise, deposits may drop into
cylinder and damage engine.
Disassembly:
Spark plug cap.◎
Spark plug.◎
Inspection:
(1) Install cylinder pressure gauge.
(2) Full open fuel valve.
(3) Ignite the starter motor by pressing the start
button and measure cylinder pressure.
Note:
(1) Cylinder pressure
*BH8 / BR8 / BF8*
125c.c. engine
12.8 - 570 kg/cm
2
-rpm.
*BR9 / BF9*
151c.c. engine
11.7 - 700 kg/cm
2
-rpm.
(2) Reasons of too high cylinder pressure:
A. Carbon deposits at combustion
chamber.
B. Carbon deposits on piston top surface.
(3) Reasons of too low cylinder pressure:
A. Valve gap too small.
B. Worn valve seat or seat is not
completely closed.
C. Incorrect valve – timing.
D. Leakage due to worn cylinder gasket.
E. Worn piston ring.
F. Worn piston and cylinder wall.
(4) Torque on spark plug 100 ~ 120 kg-cm.
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