SERVICE INFORMATION
PB-251
PB-255ES
ES-255ES
8
2-3 Adjusting carburettor
1. Start engine and warm it up alternating engine
speed between WOT and idle every 10 seconds
for 1 minute.
2. Adjust idle mixture needle (A) with 2.5 mm blade
screwdriver (E) to reach maximum engine speed
just before drop off.
3. Set idle speed to 3,500 r/min on PB-251, to 3,400
r/min on PB-255ES and ES-255ES by turning idle
adjust screw (D). Engine speed should be stable
at 3,500 +/- 30 r/min on PB-251, at 3,400 +/- 30
r/min on PB-255ES and ES-255ES after idle adjust
screw adjustment.
4. Turn idle mixture needle (A) anticlockwise to
reduce idle speed 400 to 600 r/min in the range
of 2,900 to 3,100 r/min on PB-251, 2,800 to 3,000
r/min on PB-255ES and ES-255ES.
NOTE :
Engine speed must be allowed to stabilize
a minimum of 20 seconds after each adjustment
of L mixture needle to assure accurate tachometer
readings.
5. Adjust hi speed mixture needle (B) to obtain
maximum WOT engine speed just before lean drop
off using 2.5 mm blade screwdriver.
6. Turn hi speed mixture needle (B) anticlockwise
to reduce WOT engine speed 10-20 r/min. Mini-
mum WOT engine speed after adjusting should be
over 7,200 r/min.
7. PB-251 with fan head blower pipe: Start engine,
and verify engine idle speed ranges from 2,800 to
3,400 r/min, and WOT engine speed ranges from
7,200 to 7,500 r/min.
PB-255ES with fan head blower pipe: Start
engine, and verify engine idle speed ranges from
2,700 to 3,300 r/min, and WOT engine speed
ranges from 7,200 to 7,500 r/min.
ES-255ES with vacuum attachment: Remove
fan head blower pipe, and install vacuum pipe and
bag. Start engine, and verify engine idle speed
ranges from 2,500 to 3,100 r/min, and WOT engine
speed ranges from 6,000 to 6,500 r/min.
When final adjustment is completed, the engine
should idle, accelerate smoothly, and attain WOT
per above speci
fi
cation.
8. After adjusting carburettor, insert and secure
new plug(s) (F) P005-001270 deep in the needle
holes per the Emission regulation using limiter plug
tool.
NOTE :
The initial carburettor settings for idle ad-
just screw, idle and hi mixture needles are intended
to start and run the engine before
fi
nal carburetor
adjustments are made to conform the unit to meet
Emission Directive. Actual turns required for en-
gine operation may vary.
(A)
(E)
(D)
(B)
(F)
(C)
