Bosch PB-650 User manual

Ord. No. 403-12
REVISED JUNE 2004

INTRODUCTION
This service manual contains information for
service and maintenance of ECHO POWER
BLOWER, model PB-650 (Serial Number up to
35999999) and PB-750 (Serial Number up to
35999999).
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.

TABLE OF CONTENTS
PB-650
PB-750 1
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 ............................. 5
1-5 Service limits................................................... 6
1-6 Special tools ................................................... 7
2 STARTER SYSTEM ............................................ 8
2-1 Removing starter drum and rope .................... 9
2-2 Replacing rope guide .................................... 10
2-3 Installing rewind spring ................................. 10
2-4 Installing starter drum and rope..................... 11
2-5 Increasing rope tension ................................ 12
2-6 Replacing starter pawl .................................. 12
3 IGNITION SYSTEM ........................................... 13
3-1 Troubleshooting guide .................................. 13
3-2 Testing spark................................................. 14
3-3 Checking spark plug ..................................... 14
3-4 Replacing spark plug cap and coil................ 15
3-5 Checking coil resistance ............................... 15
3-6 Checking ignition switch ............................... 16
3-7 Checking flywheel magnets .......................... 16
3-8 Replacing ignition coil ................................... 16
3-9 Setting pole shoe air gaps ............................ 17
3-10 Assembling dust cover and lead .................. 17
4 FUEL SYSTEM .................................................. 18
4-1 Cleaning air filter ........................................... 19
4-2 Checking fuel cap and strainer ..................... 19
4-3 Adjusting carburetor ..................................... 20
4-4 Testing carburetor ......................................... 21
4-5 Checking fuel tank and vent ......................... 22
4-6 Replacing fuel line and grommet .................. 22
4-7 Checking metering lever ............................... 23
4-8 Checking inlet needle valve .......................... 23
4-9 Checking diaphragm and others .................. 24
4-10 Removing main jet ........................................ 24
4-11 Checking pulse passages............................. 25
4-12 (Option) Assembling heavy duty air cleaner kit .. 25
5 HANDLE AND CONTROL SYSTEM ................ 26
5-1 Adjusting handle position.............................. 26
5-2 Removing handle .......................................... 26
5-3 Replacing throttle wire and switch ................ 27
5-4 Adjusting throttle control lever friction .......... 27
5-5 Assembling handle ....................................... 27
5-6 Positioning throttle wire and tube ................. 27
5-7 Adjusting throttle wire ................................... 28
5-8 (Option) Assembling static protection kit ...... 28
6 BACKPACK FRAME.......................................... 29
6-1 Replacing back cushion and harness........... 29
6-2 Removing backpack frame ........................... 30
6-3 Checking rubber cushions ............................ 30
7 BLOWER SYSTEM ........................................... 31
7-1 Replacing elbow blowing pipe ...................... 31
7-2 Replacing fan case grid ................................ 32
7-3 Separating fan case and engine ................... 32
7-4 Assembling fan and fan case ....................... 33
7-5 Assembling engine unit on backpack frame ..... 34
8 ENGINE ............................................................. 35
8-1 Testing cylinder compression ....................... 35
8-2 Cleaning cooling air passage ....................... 36
8-3 Checking muffler and exhaust port of cylinder ... 36
8-4 Testing crankcase and cylinder sealings ...... 37
8-5 Checking cylinder ......................................... 38
8-6 Removing flywheel ....................................... 38
8-7 Checking woodruff key for flywheel .............. 38
8-8 Installing flywheel ......................................... 39
8-9 Checking piston and piston ring ................... 39
8-10 Disassembling crankcase ............................. 40
8-11 Removing main ball bearing and oil seal ..... 40
8-12 Assembling main ball bearing ...................... 41
8-13 Assembling crankshaft and crankcase ......... 41
8-14 Assembling oil seal ....................................... 42
8-15 Assembling piston rings on piston ................ 42
8-16 Installing piston ............................................. 43
8-17 Installing cylinder .......................................... 43
9 MAINTENANCE GUIDE.................................... 44
9-1 Troubleshooting guide .................................. 44
9-2 Service intervals ........................................... 46
9-3 Disassembly chart ........................................ 47
INDEX .................................................................... 48

SERVICE INFORMATION PB-650 PB-750
2
1 SERVICE INFORMATION
1-1 Specifications
Model PB-650 PB-750
Dimensions Length* mm(in) 375 (14.8)
Width* mm(in) 470 (18.5)
Height* mm(in) 527 (20.8)
Dry weight** kg(lb) 10.7 (23.6) 11.4 (25.1)
Engine Type KIORITZ, air-cooled, two-stroke, single cylinder
Rotation Counterclockwise as viewed from the output end
Displacement cm3(in3) 63.3 (3.863)
Bore mm(in) 48.0 (1.89s)
Stroke mm(in) 35.0 (1.38)
Compression ratio 6.3
Carburetor Type Diaphragm, horizontal-draught, with primer (purge pump)
Model Walbro WYK-150 Walbro WYK-179
Ignition Type CDI (Capacitor discharge ignition) system
Spark plug BPM8Y
Starter Type Automatic rewind
Rope diameter x length mm(in) 3.5 x 1000 (9/64 x 39 1/2)
Fuel Type Premixed two-stroke fuel
Mixture ratio 50 : 1 (2 %)
Petrol Minimum 89 octance petrol (RON)
Two-stroke air cooled engine oil ISO-L-EGD (ISO/CD13738), JASO FC
Tank capacity L (U.S.fl.oz.) 2.0 (67.64)
Throttle Throttle control type Trigger type with lock
Throttle lever location Adjustable-tube mounted
Blower Fan type Centrifugal, single stage
Max. air volume (with pipes)
m3/min (ft3/min) 17 (600.35)**
Max. air velocity (with pipes)
m/s (mph) 97 (217)***
Discharge ID mm (in) 62 (2.441)
ID : Inner diameter.
* Without blower pipes.
** With straight pipes.
*** With taper pipe.

SERVICE INFORMATION
PB-650
PB-750 3
1-2 Technical data
Model PB-650 PB-750
Engine
Idling speed r/min 2200 - 2800
Wide open throttle speed r/min 7000
Compression pressure MPa (kgf/cm2) (psi) 0.8 (8.0) (115)
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1000 r/ min kV 12
Secondary coil resistance kΩ1.2 - 1.8
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing °BTDC 30
Carburetor
Venturi size mm(in) 15.0 (0.591)
Throttle bore mm(in) 15.0 (0.591)
Main jet #58.5 #50
Idle adjust screw initial setting trun in* 1 1/2
Test Pressure, minimum MPa (kgf/cm2) (psi) 0.05 (0.5) (7.0)
Metering lever height mm(in) 1.5 (0.06) lower than diaphragm seat
BTDC: Before top dead center.s
* Set idle speed screw to contact throttle plate before initial setting.
** Screw in idle mixture needle from initial thread engagement (at the point that the clicking sound is heard).

SERVICE INFORMATION PB-650 PB-750
4
1-3 Torque limits
Descriptions Size kgf• cm N•m in•lbf
Starter Starter pawl assembly M 10 80 - 100 8 - 10 70 - 90
system Starter case M 5*** 35 - 50 3.5 - 5.0 30 - 45
Ignition Flywheel M 10 200 - 240 20 - 24 175 - 210
system C.D.I module M 5 60 - 100 6 - 10 50 - 90
Fuel Spark plug M 14 150 - 170 15 - 17 130 - 150
system Carburetor M 5 40 - 55 4.0 - 5.5 35 - 48
Intake insulator M 5 35 - 45 3.5 - 4.5 30 - 40
Fuel tank M 5 20 - 40 2 - 4 17 - 35
Engine Crankcase M 5 70 - 110 7 - 11 60 - 95
Cylinder M 5 70 - 110 7 - 11 60 - 95
Engine plate M 5* 20 - 40 2 - 4 17 - 35
Engine mount M 6 100 - 150 10 - 15 90 - 130
Cylinder cover M 5 40 - 55 4.0 - 5.5 35 - 48
Engine cover M 5** 20 - 40 2 - 4 17 - 35
Muffler M 6*** 110 - 150 11 - 15 95 - 130
Muffler bracket M 5 70 - 110 7 - 11 60 - 95
Muffler insulator M 5* 20 - 40 2 - 4 17 - 35
Others Fan M 5 50 - 75 5.0 - 7.5 45 - 65
Fan case M 5 ** 40 - 55 4.0 - 5.5 35 - 48
Blower grid M 5** 20 - 40 2 - 4 17 - 35
Cushion
Frame side M 5*** 20 - 40 2 - 4 17 - 35
Fan case side Top M5** 20-40 2-4 17-35
Bottoms M 5** 80 - 100 8 - 10 70 - 90
Main pipe M 5 20 - 40 2 - 4 17 - 35
High tension lead clip M 5** 40 - 50 4 - 5 35 - 45
Harness fixture M 5** 20 - 40 2 - 4 17 - 35
Trigger bracket fixture†M 5 20 - 30 2 - 3 17 - 26
Throttle lever†† M 6 20 - 30 2 - 3 17 - 26
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
* Tapping screw
** Tapping bolt
*** Apply thread locking sealant (See next page)

SERVICE INFORMATION
PB-650
PB-750 5
1-4 Special repairing materials
Material Location Remarks
Grease Rewind spring
Starter center post Lithium based grease
Oil seal inner lips
Thread locking sealant Ball bearing Loctite #675 or equivalent
Muffler Loctite #242, ThreeBond #1327 or equivalent
Starter case Loctite #222, ThreeBond #1344N or equivalent
Cushion (Frame side) Loctite #222, ThreeBond #1344N or equivalent

SERVICE INFORMATION PB-650 PB-750
6
Description mm(in)
A Cylinder bore When plating is worn and aluminum can be seen
B Piston outer diameter Min. 47.95 (1.888)
C Piston pin bore Max. 10.03 (0.395)
D Piston ring groove, 1st Max. 1.65 (0.065)
2nd Max. 1.6 (0.063)
E Piston ring side clearance Max. 0.1 (0.004)
F Piston pin outer diameter Min. 9.98 (0.393)
G Piston ring width Min. 1.45 (0.057)
H Piston ring end gap Max. 0.5 (0.02)
K Con-rod small end bore Max. 14.025 (0.552)
L Crankshaft runout Max. 0.05 (0.002)
5K249 5K250
5K251 5K016 5K042
5K248
5K247
5K252
5K219 5K220
ABCD
EFGH
KL
1-5 Service limits

SERVICE INFORMATION
PB-650
PB-750 7
a
1.5
1.65
1.3
0.4
a
20
20
40
40
60
60
80
80
120
120
140
140
160
160
180
180
20
20
100
100
Key Part Number Description Used for:
1 897801-33330 Tachometer PET-1000 4-3
2 895115-00330 Magneto wrench 3-9
3 895610-79920 L-hex wrench (4 mm)
4 895611-79920 L-hex wrench (5 mm)
5 897501-03938 Puller 8-6
6 897537-30130 Piston stopper 2-6, 7-3, 8-6, 8-8
7 897563-19830 Metering lever gauge 4-7
8 897558-02830 T-socket wrench(8mm)
9 897558-10230 T-socket wrench(10mm)
10 897701-14732 Bearing tool 8-11, 8-12
11 897702-30131 Piston pin tool 8-9, 8-16
12 897712-07930 2-pin wrench 2-6
13 897719-02830 Piston holder 8-9, 8-16
14 897726-21430 Oil seal tool 8-14
15 897800-79931 Spark tester 3-2
16 897803-30131 Pressure tester 4-4, 4-5, 8-4
17 897826-16131 Rubber plug 8-4
18 897827-16131 Pressure plate 8-4
19 897834-79930 Rubber plug 8-4
20 897835-16131 Pressure connector 8-4
21 91007 Compression gauge 8-1
153: a=4mm
4: a=5mm
6
2
78:
a = 8 mm
9: a = 10 mm
10 11 12
1413 15 16 17
1918 20
1-6 Special tools
21

8STARTER SYSTEM PB-650
PB-750
R
L
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
(H)
(A)
(B)
(C)
(D)
(E)
(G)
(F)