21-25F-00
PB-251, PB-255ES, ES-255ES
1
2
INTRODUCTION
We are constantly working on technical improvement of our products. For this reason,
technical data, equipment and design are
subject to change without notice. All specifications and directions in this SERVICE
DATA are based on the latest products information available at the time of publication.
INDEX
CONTENTS
1 SERVICE INFORMATION
1-1 Specifi cation ............................................... 2
1-2 Technical data ............................................. 3
1-3 Torque limits................................................ 4
1-4 Special repairing materials ......................... 4
1-5 Service limits............................................... 5
1-6 Special tools ............................................... 6
CARBURETTOR ADJUSTMENT PROCEDURE
2
2-1 General adjusting rules ............................... 7
2-2 Presetting idle adjust screw, idle mixture
and hi speed (H) mixture needle
2-3 Adjusting carburettor................................... 8
Reference No.
.............................. 2
.......................... 7
21-25F-00
page
.. 7
needle
ISSUED: 200801
PB-251
PB-255ES
2
1 SERVICE INFORMATION
1-1 Specifi cations
Model PB-251 PB-255ES ES-255ES
Dimensions Length* mm(in) 340 (13.4)
Width* mm(in) 265 (10.4) 260 (10.2)
Height mm(in) 350 (13.8)
Dry weight with blower pipe** kg(lb) 4.5 (9.9) 4.8 (10.5) ---
with vacuum pipe and bag*** kg(lb) --- --- 5.9 (12.9)
Engine Type KIORITZ, air-cooled, two-stroke, single cylinder
Rotation Anticlockwise as viewed from the output end
Displacement cm
Bore mm(in) 34.0 (1.34)
Stroke mm(in) 28.0 (1.10)
Compression ratio 7.0
Carburettor Type
Model ZAMA RB-K85
Ignition Type CDI (Capacitor discharge ignition) system
Spark plug BPMR8Y
Exhaust Muffl er type Spark arrestor muffl er with catalyst
Starter Type Automatic rewind ES (effortless start)
Rope diameter x length mm(in) 3.0 x 815 (1/8 x 32.1)
Fuel Type
Mixture ratio 50 : 1 (2%)
Petrol Minimum 89 octane
Two-stroke engine oil
Tank capacity L (U.S.fl .oz.) 0.5 (16.9)
Blower Fan type Centrifugal, single stage
Blower pipe type Fan head
Max. air volume (with pipes)
m
Max. air velocity (with pipes)
m/s (mph)
Blower nozzle size, (inner) mm (in) 113 x 24 (4.5 x 0.94) oval shape
SERVICE INFORMATION
3
(in3) 25.4 (1.55)
Rotary type : Diaphragm, horizontal-draught, with primer purge bulb
Variable Slope Timing (VST) : Slope advance ignition
system combined with electronic speed governor
†
Premixed two-stroke fuel
3
/min ( ft3/min)
ISO-L-EGD (ISO/CD13738), JASO FC/FD
8.5 (300) 9.2 (325)
71 (159) 67 (150)
ES-255ES
*Without blower pipes **With all blower pipes
***With vacuum pipe and bag
†
Refer to Operator’s manual.
PB-251
PB-255ES
ES-255ES
1-2 Technical data
Model PB-251 PB-255ES ES-255ES
Engine
Idling speed r/min 2800 - 3400* 2700 - 3300* 2500 - 3100**
Wide open throttle speed r/min 7200 - 7500* 6000 - 6500**
Compression pressure MPa (kgf/cm
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1500 r/min kV 15
Primary coil resistance Ω 160 - 400
Secondary coil resistance kΩ 2.5 - 3.2
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 1000 r/min °BTDC 7
at 3000 r/min °BTDC 18
at 7000 r/min °BTDC 31
Carburettor
Idle mixture needle initial setting turns back 4 1/8
H mixture needle initial setting turns back 7/8
Idle adjust screw initial setting turns back 1 5/8
Test Pressure, minimum MPa (kgf/cm2) (psi) 0.05 (0.5) (7.0)
Metering lever height mm(in) 0.1 - 0.25 (0.004 - 0.010) lower than diaphragm seat
SERVICE INFORMATION
2
) (psi) 0.87 (8.9) (126)
3
BTDC: Before top dead centre.
*With fan head blower pipe.
** With vacuum pipe and bag.
PB-251
PB-255ES
4
1-3 Torque limits
Descriptions
Starter Starter pawl M 8* 130 - 150 13 - 15 115 - 130
system
Ignition Ignition coil M 4 35 - 45 3.5 - 4.5 30 - 40
system
Fuel Carburettor insulator M 5 50 - 70 5 - 7 45 - 60
system
Engine Crankcase M 5 70 - 110 7 - 11 60 - 95
Cylinder M 5** 70 - 110 7 - 11 60 - 95
Cylinder cover M 5 60 - 80 6 - 8 50 - 70
Cylinder cover with lead M 5 40 - 60 4 - 6 35 - 50
Engine mount M 4* 30 - 45 3 - 4.5 25 - 40
Muffl er M 5 70 - 80 7 - 8 60 - 70
Muffl er cover M 5* 30 - 45 3 - 4.5 25 - 40
Others Outer fancase M 5
Fan M 8 140 - 160 14 - 16 120 - 140
Fan hub M 8* 160 - 200 16 - 20 140 - 175
Regular bolt, nut and screw M 3 6 - 10 0.6 - 1 5 - 9
M 5 25 - 45 2.5 - 4.5 22 - 40
M 6 45 - 75 4.5 - 7.5 40 - 65
M 8 110 - 150 11 - 15 95 - 130
Starter case M 5 40 - 55 4.0 - 5.5 35 - 50
Spark plug M 14 130 - 170 13 - 17 114 - 150
Carburettor M 5 30 - 45 3 - 4.5 25 - 40
M 4 15 - 25 1.5 - 2.5 13 - 22
SERVICE INFORMATION
Size
†
kgf•cm
20 - 40 2 - 4 17 - 35
N•m
ES-255ES
in•lbf
* Apply thread locking sealant (See below)
** The torque differences among four bolts should not exceed 20 kgf•cm (N•m, 17in•lbf) on one cylinder or crank-
case.
†
Tapping screw
1-4 Special repairing materials
Material
Thread locking sealant Engine mount
Fun hub
Starter pawl
Muffl er cover
Grease Rewind spring
Starter centre shaft
Location
Loctite # 242, ThreeBond 1324 or equivalent
Loctite # 222, ThreeBond 1342 or equivalent
Lithium based grease or ECHO LUBE
Remarks
TM
PB-251
5K016
5K263 5K264 5K265
5K266
5K204
5K017
5K219
5K171
5K267
PB-255ES
ES-255ES
1-5 Service limits
ABCD
EFGH
SERVICE INFORMATION
5
KL
Description
A Cylinder bore When plating is worn and aluminium can be seen
B Piston outer diameter Min. 33.91 (1.335)
C Piston pin bore Max. 8.035 (0.3163)
D Piston ring groove Max. 1.3 (0.051)
E Piston ring side clearance Max. 0.1 (0.004)
F Piston pin outer diameter Min. 7.980 (0.3142)
G Piston ring width Min. 1.15 (0.045)
H Piston ring end gap Max. 0.5 (0.02)
K Con-rod small end bore Max. 12.000 (0.4724)
L Crankshaft runout Max. 0.03 (0.001)
mm (in)
6
1-6 Special tools
1
PB-251
PB-255ES
SERVICE INFORMATION
2
3
4
ES-255ES
5
9
13
14
6
10
15
7
11
8
12
#.014 = .35mm
Ignition Air Gap Gauge
P/N 91004
16
50
0.4
0
0.8
0
1.2
MPa
1.
ECHO
Key Part Number Description Used for:
1 897801-33330 Tachometer PET-1000 Measuring engine speed
2 363018-00310 Washer Installing crankcase oil seal of starter side
3 895610-79920 L-hex wrench (4 mm) Removing and installing hex. socket bolts (M5)
4 897603-23030 PTO shaft puller Removing driven (PTO) shaft
5 897701-06030 Bearing wedge Removing ball bearings on crankshaft
6 897701-14732 Bearing tool Removing and installing crankcase ball bearings
7 897702-30131 Piston pin tool Removing and installing piston pin
(Use 8 mm dia. adapter.)
8 91004 Module air gap gauge Adjusting pole shoe air gaps
9 897712-04630 2-pin wrench Removing and installing pawl carrier
10 897726-16431 Oil seal tool Installing crankcase oil seals
11 990511-30023 Spark tester Checking ignition system
12 897803-30133 Pressure tester Checking carburettor and crankcase leakages
13 900100-08008 Bolt Removing magneto rotor (fl ywheel)
14 433019-12330 Flange nut Removing magneto rotor (fl ywheel)
15 91037 Compression gauge Measuring cylinder compression
16 91020 Limiter plug tool Removing and installing plug
PB-251
PB-255ES
ES-255ES
2 CARBURETTOR ADJUSTMENT PROCEDURE
2-1 General adjusting rules
A. Before starting the unit for adjustment, check the following items.
1. The correct spark plug must be clean and properly gapped.
2. The air fi lter element must be clean and properly installed.
3. The muffl er exhaust port must be clear of carbon.
4. The fuel lines, tank vent and fuel fi lter are in good condition and clear of debris.
SERVICE INFORMATION
7
(A)
RON
) and properly mixed at 50 : 1 with “ISO L-EGD” or “JASO FC/
Tools Required : Small screwdriver with 2.5
mm blade, P/N 897801-33330 electronic tachometer, P/N 91020 limiter plug removal tool.
Parts Required : (2) P/N P005-001270 limiter
plugs.
1. Remove plugs from Idle mixture needle hole (A)
and H mixture needle hole (B) using limiter plug
tool (C) as follows.
(1)Put limiter plug tool (C) on limiter plug in mixture
needle hole.
5. The fuel is fresh ( > 89 octane :
FD” 2 stroke oil.
6. All blower pipes (fan head type) are installed for proper engine loading. ES-255ES should be blower
setting.
B. Start and run engine for 3 minutes alternating rpm between WOT for 50 seconds and idle for 10
seconds. Adjust idle speed screw to 3,000 +/- 100 r/min. If engine does not run correctly after this adjustment, proceed to the next step 2-2.
IMPORTANT : After adjusting carburettor according to the steps 2-2 and 2-3, the limiter plug(s)
must be installed in Idle and hi speed mixture needle to comply with Emission Directive.
2-2 Presetting idle adjust screw, Idle mixture needle and hi speed (H) mixture needle
(D)
(B)
(C)
(1)
(2)
(3)
(D)
(A)
(G)
Fig1
(2)Screw limiter plug tool anticlockwise 2 turns into
limiter plug pushing the tool against the plug to engage tool threads.
(3)Pull out limiter plug tool with the limiter plug
from mixture needle hole.
(4)Repeat plug removal procedure for the other
mixture needle.
NOTE : If the plug is damaged and left in the hole,
use a needle or pin-shaped tool to remove deformed plug pieces.
2. Turn hi speed mixture needle (B) clockwise until lightly seated. And then turn hi speed mixture
needle anticlockwise 7/8 turns. Turn idle mixture
needle (A) clockwise until lightly seated. And then
turn L mixture needle anticlockwise 4 1/8 turns.
3. Turn idle adjust screw (D) clockwise until its
head touches boss (G) as shown Fig 1. Then turn
idle adjust screw (D) anticlockwise 1 5/8 turns.
8
2-3 Adjusting carburettor
(E)
(D)
SERVICE INFORMATION
1. Start engine and warm it up alternating engine
speed between WOT and idle every 10 seconds
for 1 minute.
(A)
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.
PB-251
PB-255ES
ES-255ES
(B)
NOTE :
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. Minimum 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.
Engine speed must be allowed to stabilize
(F)
(C)
When final adjustment is completed, the engine
should idle, accelerate smoothly, and attain WOT
per above specifi 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 :
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 engine operation may vary.
The initial carburettor settings for idle ad-
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