Echo PB-251 User manual

Ord. No. 403-16

INTRODUCTION
This service manual contains information for
service and maintenance of ECHO POWER
BLOWER, model PB-251.
For systematic diagnosis, to avoid extra work and
time loss, please refer to “Troubleshooting guide”
that describes problems, testings, remedies and
references. We recommend you make use of
Operator’s Manual and Parts Catalog together with
this manual when servicing.
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,
illustrations and directions in this manual are based
on the latest products information available at the
time of publication.

PB-251 1 TABLE OF CONTENTS
Page Page
1 SERVICE INFORMATION ................................... 2
1-1 Specifications.................................................. 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
2 STARTER SYSTEM............................................. 7
2-1 Removing starter drum and rope .................... 7
2-2 Installing rewind spring ................................... 9
2-3 Installing starter drum and rope .................... 10
2-4 Increasing rope tension ................................. 11
2-5 Replacing starter pawl ...................................11
3 IGNITION SYSTEM ........................................... 13
3-1 Troubleshooting guide .................................. 14
3-2 Testing spark................................................. 15
3-3 Checking spark plug ..................................... 15
3-4 Replacing spark plug cap and coil................ 16
3-5 Checking coil resistance ............................... 16
3-6 Checking ignition switch ............................... 17
3-7 Replacing ignition switch .............................. 17
3-8 Replacing ignition coil ................................... 19
3-9 Setting pole shoe air gaps ............................ 19
3-10 Checking flywheel and key ........................... 19
4 HANDLE AND CONTROL SYSTEM ................. 21
4-1 Disassembling handle and throttle control ... 22
4-2 Reassembling handle and throttle control .... 23
5 FUEL SYSTEM .................................................. 25
5-1 Cleaning air filter ........................................... 26
5-2 Checking fuel cap and fuel strainer .............. 26
5-3 Checking fuel tank and tank vent ................. 27
5-4 Replacing fuel line, tank vent line
and grommet ................................................. 28
5-5 Adjusting carburetor ..................................... 29
5-6 Testing carburetor ......................................... 31
5-7 Checking crankcase pulse passage ............. 32
5-8 Checking metering lever ............................... 32
5-9 Checking inlet needle valve .......................... 33
5-10 Checking diaphragm and others .................. 33
5-11 Replacing carburetor .................................... 34
6 BLOWER SYSTEM ........................................... 37
6-1 Disassembling fan and fan case .................. 38
6-2 Reassembling fan and fan case ................... 38
7 ENGINE ............................................................. 39
7-1 Testing cylinder compression ....................... 40
7-2 Cleaning cooling air passages ..................... 40
7-3 Checking muffler and exhaust port............... 41
7-4 Testing crankcase and cylinder sealings ...... 42
7-5 Replacing oil seal ......................................... 43
7-6 Checking cylinder ......................................... 43
7-7 Checking piston and piston ring ................... 44
7-8 Replacing needle bearing ............................. 44
7-9 Disassembling crankcase ............................. 45
7-10 Replacing ball bearings ................................ 45
7-11 Assembling crankshaft and crankcase ......... 46
7-12 Installing piston ............................................. 46
7-13 Installing piston ring and cylinder ................. 47
7-14 Installing engine to inner fan case ................ 48
8 MAINTENANCE GUIDE .................................... 49
8-1 Service Intervals ........................................... 49
8-2 Troubleshooting guide .................................. 50
8-3 Disassembly chart ........................................ 52
INDEX .................................................................... 53

SERVICE INFORMATION PB-251
2
1 SERVICE INFORMATION
1-1 Specifications
Dimensions Length* mm(in) 330 (13.0)
Width* mm(in) 265 (10.4)
Height mm(in) 360 (14.2)
Dry weight** kg(lb) 4.5 (9.9)
Engine Type KIORITZ, air-cooled, two-stroke, single cylinder
Rotation Counterclockwise as viewed from the output end
Displacement cm3(in3) 25.4 (1.55)
Bore mm(in) 34.0 (1.34)
Stroke mm(in) 28.0 (1.10)
Compression ratio 7.0
Carburetor Type Rotary type : Diaphragm, horizontal-draught, with purge bulb
Model ZAMA RB-K85
Ignition Type CDI (Capacitor discharge ignition) system
Variable Slope Timing (VST) : Slope advance ignition
system combined with electronic speed governor
Spark plug BPM8Y
Exhaust Muffler type Spark arrestor muffler with catalyst
Starter Type Automatic rewind
Rope diameter x length mm(in) 3.0 x 815 (1/8 x 32.1)
Fuel Type †Premixed two-stroke fuel
Mixture ratio 50 : 1 (2%)
Gasoline Minimum 89 octane
Two-stroke engine oil ISO-L-EGD (ISO/CD13738), JASO M345-FC/FD
Tank capacity L (U.S.fl.oz.) 0.5 (16.9)
Blower Fan type Centrifugal, single stage
Max. air volume (with pipes) 10.9 (386)
m3/min ( ft3/min)
Max. air velocity (with pipes) 63.5 (142)
m/s (mph)
Discharge ID†† mm(in) 62 (2.44)
*Without blower pipes **With all blower pipes †Refer to Operator’s manual. ††ID : Inner diameter

SERVICE INFORMATIONPB-251 3
1-2 Technical data
Engine
Idling speed* rpm 2800 - 3200
Wide open throttle speed* rpm 6700 - 7200
Compression pressure MPa (kgf/cm2) (psi) 0.81 (8.3) (118)
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1500 rpm kV 15
Primary coil resistance Ω160 - 400
Secondary coil resistance kΩ2.5 - 3.2
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 1000rpm °BTDC 6.5
at 3000rpm °BTDC 17.5
at 7000rpm °BTDC 31.0
Carburetor
Idle mixture needle initial setting turns back 5 3/8
H mixture needle initial setting turns back 1 1/8
Idle adjust screw initial setting turns back** 5
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
BTDC: Before top dead center.
*With all blower pipes.
**Refer to page 7 on 2-2 initial idle adjust screw.

SERVICE INFORMATION PB-251
4
1-3 Torque limits
Descriptions Size kgf•cm 2N•m in•lbf
Starter Starter pawl M 8* 130 - 150 13 - 15 115 - 130
system Starter case M 5 40 - 55 4.0 - 5.5 35 - 50
Ignition Ignition coil M 4 35 - 45 3.5 - 4.5 30 - 40
system Spark plug M 14 150 - 170 15 - 17 130 - 150
Fuel Carburetor insulator M 5 50 - 70 5 - 7 45 - 60
system Carburetor M 5 35 - 45 3.5 - 4.5 30 - 40
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
Muffler M 5 70 - 80 7 - 8 60 - 70
Muffler cover M 5* 30 - 45 3 - 4.5 25 - 40
Others Outer fancase M 5†20 - 40 2 - 4 17 - 35
Fan M 8 140 - 160 14 - 16 120 - 140
Fan hub M 8* 160 - 200 16 - 20 140 - 175
Regular bolt, nut, M 3 6 - 10 0.6 - 1.0 5 - 9
and screw M 4 15 - 25 1.5 - 2.5 13 - 22
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
1-4 Special repairing materials
Material Location Remarks
Thread locking sealant Engine mount Loctite # 242, ThreeBond 1324 or equivalent
Fun hub
Starter pawl Loctite # 222, ThreeBond 1342 or equivalent
Muffler cover
Grease Rewind spring Lithium based grease or ECHO LUBETM
Starter center shaft
* Apply thread locking sealant (See below)
** The torque differences among four bolts should not exceed 20 kgf•cm (2N•m, 17in•lbf) on one cylinder or crankcase.
†Tapping screw

SERVICE INFORMATIONPB-251 5
1-5 Service limits
Description mm (in)
A Cylinder bore When plating is worn and aluminum can be seen
B Piston outer diameter Min. 33.91 (1.335)
C Piston pin bore Max. 8.030 (0.3161)
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. 11.988 (0.4719)
L Crankshaft runout Max. 0.05 (0.002)
5K016
5K263 5K264 5K265
5K266
5K204
5K017
5K219
5K171
5K267
ABCD
EFGH
KL

SERVICE INFORMATION PB-251
6
Key Part Number Description Used for:
1 897801-33330 Tachometer PET-1000 Measuring engine speed
2 897826-16131 Pressure plug Testing crankcase and cylinder sealings
3 897827-16131 Pressure plate Testing crankcase and cylinder sealings
4 897835-16131 Pressure connector Testing crankcase and cylinder sealings
5 363018-00310 Washer Installing crankcase oil seal of starter side
6 897719-02830 Piston holder Making piston steady to remove and install piston / ring
7 897705-11520 Needle bearing tool Removing and installing connecting rod needle bearing
8 897701-14732 Bearing tool Removing and installing crankcase ball bearings
9 897702-30131 Piston pin tool Removing and installing piston pin (Use 8 mm dia. adapter.)
10 91004 Module air gap gauge Setting pole shoe air gaps
11 895615-10860 L-hex wrench (6 mm) Removing and installing pawl carrier
12 897726-16431 Oil seal tool Installing crankcase oil seals
13 897800-79931 Spark tester Checking ignition system
14 897803-30133 Pressure tester Checking carburetor and crankcase leakages
15 900100-08008 Bolt Removing magneto rotor (flywheel)
16 433019-12330 Flanged nut Removing magneto rotor (flywheel)
17 91007 Compression gauge Measuring cylinder compression
18 91020 Limiter plug tool Removing and installing limiter plug
19 897537-30130 Piston stopper To stop crankshaft rotation when removing and installing
pawl carrier, fan, flywheel
20
40
60
80 120
140
160
180
20
100
ECHO
Ignition Air Gap Gauge
#.014 = .35mm
P/N 91004
1-6 Special tools
1
8
16
9
17
4
10
12
7
11 14
15
13
26
18
35
19

STARTER SYSTEM
PB-251 7
2 STARTER SYSTEM
( A ) Pawl carrier
( B ) Starter pawl
( C ) Starter drum
( D ) Rewind spring
( E ) Starter case
( F ) Starter rope
( G ) Rope guide
( H ) Starter grip
( I ) Starter rope clip
2-1 Removing starter drum and rope
1. Remove two muffler cover bolts (A), and muffler
cover from engine body.
2. Remove three starter assembly bolts (B), and
starter assembly from engine body.
(C)
(D)
(E)
(F)
(A)
(B)
(G)
(H)
(I)
(A)
(B)

8STARTER SYSTEM PB-251
2-1 Removing starter drum and rope (continued)
3. Pull out starter rope about 30 centimeters (12in)
and hold starter drum with finger.
4. Pull out starter rope in starter case.
5. Rotate starter drum clockwise to releace tension
of rewind spring with the rope hooked at notch (A).
6. Pull out starter rope clip (B) and starter rope knot
(C) from starter grip.
7. Cut off or untie the knot (C).
8. Remove screw (D) and washer.
WARNING DANGER
Be careful when removing starter drum;
rewind spring may unwind unexpectedly.
9. Slowly, lift up starter drum (E) from starter case.
10. Unwind starter rope from starter drum. Remove
the knot from the end of rope, and remove rope from
drum.
(C)
(D)
(E)
(A)
(B)

STARTER SYSTEM
PB-251 9
2-2 Installing rewind spring
Use of eye protection and safety gloves are
strongly recommended while working on re-
wind spring.
If rewind spring unwinds unexpectedly, follow steps
1) to 4).
1) Wind rewind spring by hand. Then draw out
the end of spring (A) as shown.
2) Wind drawn-out part (B) to wound part (C),
keeping wound part tight by hand (D) as shown.
Repeating this procesure several times, wind
rewind spring smaller than inner diameter of
starter case.
3) Retain rewind spring with longnose pliers as
shown. Set rewind spring in starter case, hooking
the outer hook (E) to the holder (F) of starter case.
4) Apply small amount lithium based grease to
outside of rewind spring.
NOTE: Rewind spring supplied as spare part is
shipped in temporary retainer. Retainer should be
removed when installing.
To install new spring wound in retainer:
1) Align outer hook of spring in retainer with the
holder (F) of starter case.
2) Push spring down into the bottom of case,
keeping spring strongly pressed against case.
3) Spring should fall into case, and retainer is
detached.
(F)
(F) (E)
(A)
(B)
(C)
(D)

10 STARTER SYSTEM PB-251
2-3 Installing starter drum and rope
1. When installing new starter rope, singe both ends
of rope to prevent fraying.
WARNING DANGER
Do not use flame in an area where gasoline
is stored or flammable gases may exist.
2. Pass one end of starter rope through the opening
in starter drum and make a knot (A).
3. Pull starter rope to seat the knot in starter drum.
4. Pack excess rope (B) into the recess (C) of drum.
5. Pass loose end through rope guide (D), starter
grip (E) and starter rope clip (F).
6. Make another knot at the end of starter grip side.
Then press the knot and starter rope clip into the
recess of grip.
7. Bend the inner loop of rewind spring so that the
inner hook lightly touches center post (G).
8. Lubricate center post (G) and the center hole of
starter drum with grease (use any good quality
lithium based grease).
9. Wind starter rope onto starter drum about three
turns counterclockwise as viewed from the pawl
catcher (H) side.
10. Install starter drum in starter case. Make sure
that starter drum engages with the inner hook of
rewind spring.
11. Apply a drop of thread locking sealant (Loctite
#222 or equivalent) on top of screw (I). Install washer
(J) and screw (I) holding starter drum in case.
(C)
(D)
(E)
(F)
(A)
(B)
(G)
(H)
(J)
(I)

STARTER SYSTEM
PB-251 11
2-4 Increasing rope tension
1. Pre-tension rewind spring by rotating starter drum
counterclockwise three turns with starter rope
hooked at notch (A).
2. Hold starter drum to prevent it from rewinding,
and pull starter grip, to take up the slack of rope.
3. Release starter grip slowly.
4. Pull starter several times to check rewind spring
tension.
5. If starter is not rewinding fully, rotate starter drum
counterclockwise one extra turn with starter rope
hooked at the notch (A).
6. Pull out starter rope all the way, and check that
starter drum can be rotated an additional one (or
more) turn counterclockwise.
7. If starter drum cannot be rotated one turn, re-
duce tension by rotating starter drum clockwise one
turn with starter rope hooked at the notch (A).
2-5 Replacing starter pawl
1. Check starter pawls (A) and pawl springs (B). If
defective, replace them as follows.
2. Clean dirt from around spark plug, and remove
spark plug.
NOTE: Do not drop dirt or dust from spark plug hole.
3. Insert piston stopper 897537-30130 (C) in the
spark plug hole by hand.
(A)
(C)
(A)
(B)

12 STARTER SYSTEM PB-251
2-5 Replacing starter pawl (continued)
5. Remove pawl carrier counterclockwise with 6mm
L hexagonal wrench 895615-10860.
6. Remove E-ring(s) (A) from starter pawl(s).
7. Insert (new) spring(s) (B) to (new) starter pawl(s),
and push starter pawl(s) into the hole(s). Then, install
E-ring(s) as shown.
8. Install pawl carrier by hand tight temporarily to
crankshaft.
9. Tighten pawl carrier clockwise with 6mm L
hexagonal wrench 895615-10860.
10. Remove piston stopper 897537-30130 from
spark plug hole. Install spark plug and spark plug
cap.
11. Install starter assembly, and other remaining
parts.
(A)
(B)
(B)

IGNITION SYSTEM
PB-251 13
3 IGNITION SYSTEM
( A ) Ignition switch
( B ) Lead terminal
( C ) Ignition switch knob
( D ) Stop lead
( E ) Stop lead grommet
( F ) Spark plug
( G ) Spark plug cap coil
( H ) Spark plug cap cover
( I ) Spark plug cap
( J ) Ignition coil
( K ) High tension lead
( L ) High tension lead
grommet
( M ) Flywheel
( N ) Fan hub
(A)
(G)
(I)
(E)
(F)
(H)
(D)
(J)
(K)
(L)
(M)
(N)
(B)
(C)

IGNITION SYSTEM PB-251
14
Not
OK
Not
OK
Not
OK
OK
OK
OK
Spark plug
Spark
plug cap/
coil
Ignition
switch
Clean /
Regap /
Replace.
Replace.
Start
OK
OK
S.T.
Not
OK
S.T.
Not
OK
Not
OK
S.T.
OK
S.T.
Not
OK
Pole
shoe air
gaps
Replace.
Not
OK
OK
OK
Not
OK
S.T.
OK
OK
Clean / Regap / Replace
spark plug.
Replace
ignition
coil.
Leads
connections
Not
OK
OK
OK
Not
OK
S.T.
Repair /
Replace.
Coil
resist-
ances
Not
OK
Remedy
Check
Not
OK
Flywheel
key
OK
R.T.
End
Not
OK
Flywheel
magnet
Replace.
Not
OK
R.T.
Not
OK
OK
OK
Replace ignition coil and / or check other
systems.
Replace flywheel.
(Check the key at the same
time. Go to Bif OK.)
OK
OK
Adjust pole shoe air gaps.
(Check flywheel magnet
at the same time. Go to
Aif OK.)
S.T.
Not
OK
A
B
S.T.: Spark test.
R.T.: Running test including actual cutting.
OK
3-1 Troubleshooting guide

IGNITION SYSTEM
PB-251 15
(A)
3-2 Testing spark
WARNING DANGER
Do not touch the spark plug while perform-
ing the test to avoid receiving electric shock.
WARNING DANGER
Do not check the spark in an area where gaso-
line is spilled or flammable gases may exist.
1. Disconnect spark plug cap from spark plug.
2. Connect spark tester 897800-79931 (A) to spark
plug and spark plug cap as shown.
3. Screw in adjuster (B) until the tips contact together
and turn back four turns to set the spark tester gap
(C) to 4 mm (0.16 in).
4. Set ignition switch to RUN position.
5. Pull starter grip several times.
6. If the spark is blue, white and steady by tester
gap, ignition system is considered good. Go to “3-3
Checking spark plug”.
7. If no spark exists or spark is red, yellow or
intermittent, continue with further tests according to
“3-1 Trouble shooting guide”.
3-3 Checking spark plug
1. Remove spark plug, check for fouling and worn,
and rounded center electrode.
2. Clean plug electrodes and insulator of
carbon deposits, or replace with new spark plug.
3. Check spark plug gap.
Standard: 0.6 to 0.7 mm (0.024 to 0.028 in).
4. If engine does not start after cranking several
times in spite of proper spark plug condition, check
if spark plug is wet or dry. If it is excessively dry or
wet, check fuel system.
GASO
LINE
(C)
(B)
(A)

IGNITION SYSTEM PB-251
16
3-4 Replacing spark plug cap and coil
1. Disconnect spark plug cap from spark plug.
Remove spark plug cap cover from spark plug cap.
2. Apply some oil in spark plug cap (A) to aid in
removing spark plug cap from high tension lead (B).
3. Pull spark plug cap away from high tension lead.
4. Check spark plug cap coil (C) for correct
connection and corrosion. Check spark plug cap for
cracks. Replace as required.
NOTE: Make sure that spark plug cap coil contacts
conductor core of high tension lead when re-
installing it.
5. Apply oil to spark plug cap and insert high tension
lead as shown until spark plug cap coil is properly
seated in the cap.
3-5 Checking coil resistance
1. Connect one probe of an ohm-meter or a
multimeter to spark plug cap coil and the other end
to some part of cylinder.
2. Measure secondary coil resistance. Resistance
should be in the range of 2.5 to 3.2 kΩ; if the value
is not in the range, replace with a new ignition coil.
(B)
(A)
(C)

IGNITION SYSTEM
PB-251 17
3-6 Checking ignition switch
1. Remove air cleaner cover and handle lid.
2. Disconnect all lead couplers in handle.
3. Connect probes of an ohm-meter or a multimeter
to ignition switch leads as shown.
4. When ignition switch is in RUN position, tester
should indicate infinite resistance.
5. When ignition switch is in STOP position, tester
should show that the circuit is in conduction state
(close circuit).
6. If ignition switch is defective, replace with a new
one.
3-7 Replacing ignition switch
1. Remove handle lid and ignition switch knob (A).
2. Disconnect couplers (B) from lead terminal (C).
3. Pull ignition switch (D) from lead terminal (C).
4. Pull lead terminal (C) out, from hole of handle at
an angle as shown.
5. If lead terminal (C) is defective, replace with new
one.
(B)
(C)
(A)
(C)
(D)
(D)

IGNITION SYSTEM PB-251
18
3-7 Replacing ignition switch (continued)
5. Insert lead terminal (C) in the hole of handle.
6. Slot new ignition switch (E) into lead terminal as
shown.
7. Connect all couplers and lead terminal. Route
leads around ribs and in grooves in handle (refer to
“4-2 Reassembling handle and throttole control”).
8. Make sure top of ignition switch (E) is correctly
engaging the hole (F) of handle.
9. Install ignition switch knob (A) and handle lid.
(E)
(F)
(C)
(E)
(A)