Inspection And Repair Procedures; Checking For Sparks Of The Spark Plug; Adjustment Of The Carburetor - Hitachi CM 75EAP Service Manual

[Bold] numbers in the descriptions below correspond to item numbers in the Parts List and exploded
assembly diagram for the Models CM 75EAP and CM 75EBP.
WARNING: Always stop the engine prior to disassembly or when replacing the cut-off wheel.

1. Checking for sparks of the spark plug

CAUTION:
• Be careful not to touch the metallic portion of Spark
Plug Ass'y BPMR7A [142] when pulling the starter
handle; otherwise, you run the risk of electric shock.
• Carefully wipe off any fuel around the plug to avoid a
sudden flash of fire.
(1) Remove Spark Plug Ass'y BPMR7A [142] from the Cylinder
[146]. Use a wire brush to clean off carbon deposits on the
electrodes of Spark Plug Ass'y BPMR7A [142], as needed.
Adjust the gap between the electrodes if necessary. Use a
cloth to wipe off any fuel on the electrodes. Remove fuel left
in the Cylinder [146], Crank Case (A) [6], and Crank Case
(B) [44] by following the procedure below.
(a) Remove the Spark Plug Ass'y BPMR7A [142] from the
Cylinder [146].
(b) Open the choke (with the Choke button [191] pushed in)
and set the Stop Switch [196] to the stop position.
(c) Open the throttle by pulling the Throttle Lever [134].
(d) Pull the starter handle several times.
(2) Insert Spark Plug Ass'y BPMR7A [142] into the Plug Cap
Cord [24] and place the electrodes in contact with the
metallic portion of the engine. Under these conditions, set
the Stop Switch [196] to the startup position and pull the
starter handle.
(3) When the above steps are all completed normally, the electrodes of Spark Plug Ass'y BPMR7A [142]
should make a snapping sound to generate sparks.

2. Adjustment of the carburetor

(1) Use the idle adjust screw to adjust the carburetor.
• Use this screw to adjust the revolutions at idling. Turning the
screw clockwise increases engine revolutions; turning it
counterclockwise decreases engine revolutions.
(2) Standard setting of the carburetor
-1
• 2,500 ± 200 min
(3) Fine adjustment
• Idling adjustment
(a) Adjust the idling revolutions after the engine is fully
warmed up. (Tip on warm-up: Let the engine idle for one
minute in half-throttled status.)
(b) Use the idle adjust screw to set revolutions so that the cut-off wheel does not start rotating while
the engine runs stably.
(c) Set idling revolutions between 2,300 and 2,700 min
approx. 2,500 min

Inspection and repair procedures

-1
.)
• Spark plug
Gap between
electrodes
(0.6 to 0.7 mm)
• Checking for sparks
• Idle adjust screw
Revolutions
decrease.
-1
by using the idle adjust screw. (Adjust to
-7-
Remove carbon here.
High voltage cord
Plug cap
[142]
Ignited sparks
Metallic portion of the engine
Idle adjust screw
Revolutions
increase.