Echo PB-251 Service 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 TABLE OF CONTENTS

1

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

Page

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

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

3-7

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

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

6 BLOWER SYSTEM ........................................... 37

6-1

6-2

Disassembling fan and fan case .................. 38

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

4 HANDLE AND CONTROL SYSTEM ................. 21

4-1 Disassembling handle and throttle control ... 22

4-2 Reassembling handle and throttle control .... 23

8 MAINTENANCE GUIDE .................................... 49

8-1 Service Intervals ........................................... 49

8-2 Troubleshooting guide .................................. 50

8-3 Disassembly chart ........................................ 52 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

INDEX .................................................................... 53

2

1 SERVICE INFORMATION

SERVICE INFORMATION PB-251

1-1 Specifications

Dimensions Length*

Width*

Height

Dry weight**

Engine Type

Rotation

Displacement

Bore

Stroke

Compression ratio

Carburetor Type

Ignition

Model

Type

Exhaust

Starter

Fuel

Blower mm(in) mm(in) mm(in) kg(lb)

330 (13.0)

265 (10.4)

360 (14.2)

4.5 (9.9)

KIORITZ, air-cooled, two-stroke, single cylinder

Counterclockwise as viewed from the output end

25.4 (1.55) cm 3 (in 3 ) mm(in) mm(in)

34.0 (1.34)

28.0 (1.10)

7.0

Rotary type : Diaphragm, horizontal-draught, with purge bulb

ZAMA RB-K85

CDI (Capacitor discharge ignition) system

Spark plug

Muffler type

Type

Rope diameter x length mm(in)

Type

Mixture ratio

Variable Slope Timing (VST) : Slope advance ignition system combined with electronic speed governor

BPM8Y

Spark arrestor muffler with catalyst

Automatic rewind

3.0 x 815 (1/8 x 32.1)

† Premixed two-stroke fuel

50 : 1 (2%)

Gasoline

Two-stroke engine oil

Tank capacity

Fan type

L (U.S.fl.oz.)

Minimum 89 octane

ISO-L-EGD (ISO/CD13738), JASO M345-FC/FD

0.5 (16.9)

Centrifugal, single stage

Max. air volume (with pipes) m 3 /min ( ft 3 /min)

Max. air velocity (with pipes) m/s (mph)

Discharge ID †† mm(in)

10.9 (386)

63.5 (142)

62 (2.44)

*Without blower pipes **With all blower pipes † Refer to Operator’s manual. †† ID : Inner diameter

PB-251 SERVICE INFORMATION

1-2 Technical data

Engine

Idling speed*

Wide open throttle speed* rpm rpm

Compression pressure

Ignition system

MPa (kgf/cm 2 ) (psi)

Spark plug gap

Minimum secondary voltage at 1500 rpm mm (in) kV

2800 - 3200

6700 - 7200

0.81 (8.3) (118)

Primary coil resistance

Secondary coil resistance

Pole shoe air gaps

Ignition timing at 1000rpm at 3000rpm at 7000rpm

Carburetor

Idle mixture needle initial setting

Ω k Ω mm(in)

° BTDC

° BTDC

° BTDC

0.6 - 0.7 (0.024 - 0.028)

15

160 - 400

2.5 - 3.2

0.3 - 0.4 (0.012 - 0.016)

6.5

17.5

31.0

turns back 5 3/8

H mixture needle initial setting

Idle adjust screw initial setting

Test Pressure, minimum

Metering lever height turns back turns back**

1 1/8

5

MPa (kgf/cm 2 ) (psi) 0.05 (0.5) (7.0) 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.

3

4

SERVICE INFORMATION PB-251

1-3 Torque limits

Descriptions

Starter Starter pawl system

Starter case

Ignition Ignition coil system

Spark plug

Fuel system

Carburetor insulator

Carburetor

Engine Crankcase

Cylinder

Cylinder cover

Cylinder cover with lead

Engine mount

Muffler

Muffler cover

Others Outer fancase

Fan

Fan hub

Regular bolt, nut, and screw

Size

M 5

M 5

M 4*

M 5

M 5*

M 5 †

M 8

M 8*

M 3

M 4

M 5

M 5

M 5

M 5

M 8*

M 5

M 4

M 14

M 5

M 6

M 8 kgf•cm

130 - 150

40 - 55

35 - 45

150 - 170

50 - 70

35 - 45

70 - 110

70 - 110

60 - 80

40 - 60

30 - 45

70 - 80

30 - 45

20 - 40

140 - 160

160 - 200

6 - 10

15 - 25

25 - 45

45 - 75

110 - 150

2N•m

13 - 15

4.0 - 5.5

3.5 - 4.5

15 - 17

5 - 7

3.5 - 4.5

7 - 11

7 - 11

6 - 8

4 - 6

3 - 4.5

7 - 8

3 - 4.5

2 - 4

14 - 16

16 - 20

0.6 - 1.0

1.5 - 2.5

2.5 - 4.5

4.5 - 7.5

11 - 15 in•lbf

115 - 130

35 - 50

30 - 40

130 - 150

45 - 60

30 - 40

60 - 95

60 - 95

50 - 70

35 - 50

25 - 40

60 - 70

25 - 40

17 - 35

120 - 140

140 - 175

5 - 9

13 - 22

22 - 40

40 - 65

95 - 130

* 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

1-4 Special repairing materials

Material Location

Thread locking sealant Engine mount

Fun hub

Starter pawl

Grease

Muffler cover

Rewind spring

Starter center shaft

Remarks

Loctite # 242, ThreeBond 1324 or equivalent

Loctite # 222, ThreeBond 1342 or equivalent

Lithium based grease or ECHO LUBE TM

PB-251

1-5 Service limits

A B

SERVICE INFORMATION

C D

5

E

5K204

F

5K263

G

5K264 5K265

H

K

5K266

L

5K016 5K017 5K267

5K219

Description

A Cylinder bore

B Piston outer diameter

C Piston pin bore

D Piston ring groove

E Piston ring side clearance

F Piston pin outer diameter

G Piston ring width

H Piston ring end gap

K Con-rod small end bore

L Crankshaft runout

5K171

Min.

Max.

Max.

Max.

Min.

Min.

Max.

Max.

Max.

mm (in)

When plating is worn and aluminum can be seen

33.91 (1.335)

8.030 (0.3161)

1.3 (0.051)

0.1 (0.004)

7.980 (0.3142)

1.15 (0.045)

0.5 (0.02)

11.988 (0.4719)

0.05 (0.002)

6

1-6 Special tools

1 2

SERVICE INFORMATION

3 4 5 6

PB-251

7 8 9 10

Air Gap Gauge

Ignition

P/N 91004

14 11 12 13

15 16 17

20

40

60 80

100

20

180

160

120

140

18

ECHO

19

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

4 897835-16131 Pressure connector

5 363018-00310 Washer

6 897719-02830 Piston holder

Testing crankcase and cylinder sealings

Testing crankcase and cylinder sealings

Installing crankcase oil seal of starter side

Making piston steady to remove and install piston / ring

7 897705-11520 Needle bearing tool

8 897701-14732 Bearing tool

Removing and installing connecting rod needle bearing

Removing and installing crankcase ball bearings

9 897702-30131 Piston pin tool

10 91004 Module air gap gauge

Removing and installing piston pin

Setting pole shoe air gaps

(Use 8 mm dia. adapter.)

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

14 897803-30133 Pressure tester

Checking ignition system

Checking carburetor and crankcase leakages

15 900100-08008 Bolt

16 433019-12330 Flanged nut

17 91007

18 91020

Compression gauge

Limiter plug tool

19 897537-30130 Piston stopper

Removing magneto rotor (flywheel)

Removing magneto rotor (flywheel)

Measuring cylinder compression

Removing and installing limiter plug

To stop crankshaft rotation when removing and installing pawl carrier, fan, flywheel

PB-251

2 STARTER SYSTEM

(C)

(I)

(F)

(H)

2-1 Removing starter drum and rope

STARTER SYSTEM

(A)

(B)

(D)

( 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

7

(G)

(E)

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.

(B)

(A)

8

STARTER SYSTEM

2-1 Removing starter drum and rope (continued)

PB-251

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).

(A)

(B)

(C)

(D)

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.

(E)

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.

PB-251

2-2 Installing rewind spring

(D)

STARTER SYSTEM

(A)

(B)

Use of eye protection and safety gloves are strongly recommended while working on rewind 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.

9

(C)

(F)

(E)

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.

(F)

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.

10

2-3 Installing starter drum and rope

STARTER SYSTEM PB-251

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.

(F)

(E)

(A)

(C)

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.

(B)

(D)

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).

(G)

(H)

(J)

(I)

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.

PB-251

2-4 Increasing rope tension

(A)

2-5 Replacing starter pawl

(B)

STARTER SYSTEM

11

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, reduce tension by rotating starter drum clockwise one turn with starter rope hooked at the notch (A).

1. Check starter pawls (A) and pawl springs (B). If defective, replace them as follows.

(A)

(C)

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.

12

2-5 Replacing starter pawl (continued)

STARTER SYSTEM PB-251

5. Remove pawl carrier counterclockwise with 6mm

L hexagonal wrench 895615-10860.

(A)

(B)

(B)

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.

PB-251

3 IGNITION SYSTEM

(B)

(A)

(C)

(N)

(K)

IGNITION SYSTEM

(D)

( 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

13

(E)

(L)

(G) (F)

(M)

(J)

(I)

(H)

14

3-1 Troubleshooting guide

IGNITION SYSTEM PB-251

Start

OK

S.T.

Not

OK

Spark plug

Not

OK

OK

Clean / Regap / Replace spark plug.

Clean /

Regap /

Replace.

S.T.

Not

OK

OK

Spark plug cap/ coil

OK

Not

OK

Replace.

S.T.

Not

OK

OK

Ignition switch

OK

Not

OK

Replace.

S.T.

Not

OK

OK

Coil resistances

OK

Not

OK

Replace ignition coil.

S.T.

Not

OK

OK

Leads connections

Not

OK

Repair /

Replace.

S.T.

Not

OK

OK

Check Remedy

Pole shoe air gaps

OK

Not

OK

Flywheel

magnet

OK

Not

OK

Adjust pole shoe air gaps.

(Check flywheel magnet at the same time. Go to

A if OK.)

Replace flywheel.

(Check the key at the same time. Go to B if OK.)

A

S.T.

Not

OK

OK

R.T.

Not

OK

OK

B

Flywheel key

OK

Not

OK

Replace.

OK

R.T.

Not

OK

Replace ignition coil and / or check other systems.

End

S.T.: Spark test.

R.T.: Running test including actual cutting.

PB-251

3-2 Testing spark

(A)

IGNITION SYSTEM

15

GASO

LINE

WARNING DANGER

Do not touch the spark plug while performing the test to avoid receiving electric shock.

(C)

(B)

WARNING DANGER

Do not check the spark in an area where gasoline 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

(A)

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.

16

3-4 Replacing spark plug cap and coil

IGNITION SYSTEM

(B)

PB-251

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.

(A)

(C)

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 reinstalling 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

k Ω ; if the value is not in the range, replace with a new ignition coil.

PB-251

3-6 Checking ignition switch

IGNITION SYSTEM

17

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).

(C)

(A)

(D)

(B)

(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.

(D)

18

3-7 Replacing ignition switch (continued)

IGNITION SYSTEM

(C)

PB-251

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”).

(E)

(F)

8. Make sure top of ignition switch (E) is correctly engaging the hole (F) of handle.

(E)

(A)

9. Install ignition switch knob (A) and handle lid.

PB-251

3-8 Replacing ignition coil

(A)

(D)

3-9 Setting pole shoe air gaps

(A)

3-10 Checking flywheel and key

IGNITION SYSTEM

19

(E)

(B)

(C)

1. Remove stop lead grommet (A) and high tension lead grommet (B) from cylinder cover.

2. Remove ignition coil (C) from cylinder.

3. Pull out stop lead (D) from ignition coil.

4. Remove high tension lead (E) from cylinder cover, and then remove spark plug cap and spark plug cap cover from high tension lead.

5. Reinstall the above parts to new ignition coil.

6. Temporarily install ignition coil and grommets to cylinder.

7. Proceed to “3-9 Setting pole shoe air gaps”.

1. Loosen ignition coil bolts and insert module air gap gauge 91004 (A) between flywheel and ignition coil.

2. Rotate flywheel until the flywheel magnets align with the ignition coil legs.

3. Hold ignition coil against module air gap gauge and tighten bolts.

Standard gaps: 0.3 - 0.4 mm (0.012 - 0.016 in)

NOTE: If air gaps are too wide, this system will not generate sufficient energy and give a weak spark or an incorrect ignition timing. If the gaps are too close, the ignition coil can interfere with the flywheel.

1. Rotate flywheel until the magnets are visible.

2. Check magnetic force of flywheel using flux meter or bridging with a screwdriver and comparing with a good one.

3. If it is defective, replace with new one.

20

3-10 Checking flywheel and key (continued)

IGNITION SYSTEM

(A)

PB-251

4. Remove spark plug, and then insert piston stopper

897537-30130 (A) by hand.

5. Remove fan hub counterclockwise with socket wrench, and then remove flywheel. If flywheel cannot be lifted off, follow steps 6 to 8.

6. To prevent crankshaft damage, use flanged nut and bolt as follows. Screw in flanged nut (B)

(433019-12330: nut size M8) 3 turns on crankshaft.

7. Screw bolt (C) (900100-08008: bolt size M8x8) in flanged nut until it bottoms.

8. Hold flywheel and tap the bolt head axially to remove flywheel.

NOTE: Do not pry flywheel from crankshaft. Damage to engine will result.

(D)

(E)

(B)

(C)

9. Check flywheel key (D) for damage. Replace with a new one if deformed.

10. Install flywheel on crancshaft so that flywheel key matches keyway (E) on crankshaft.

11. Apply thread locking sealant (Loctite #242,

ThreeBond 1324 or equivarent) to crankshaft threads and tighten fan hub.

PB-251 HANDLE AND CONTROL SYSTEM

4 HANDLE AND CONTROL SYSTEM

( A ) Handle lid

( B ) Throttle trigger

( C ) Throttle rod

( D ) Throttle cover

( E ) Ignition switch

( F ) Ground lead

( G ) Handle

( H ) Stop lead

( I ) Stop lead grommet

(D)

(A)

(B)

21

(E)

(F)

(C)

( I )

(H)

(G)

22

HANDLE AND CONTROL SYSTEM

4-1 Disassembling handle and throttle control

(A)

PB-251

1. Remove air cleaner cover and muffler cover.

2. Remove screw (A: M5x20) in order to remove handle lid.

(B)

(C)

3. Remove screw (B: M5x25) and screw (C: M5x20).

Remove handle lid.

(D)

(E)

4. Disconnect couplers (D).

5. Pull out leads from ribs of handle. Remove handle.

6. Remove throttle cover (E).

PB-251 HANDLE AND CONTROL SYSTEM

23

4-1 Disassembling handle and throttle control (continued)

(I) (H) (G) (J)

7. Pull out throttle rod end (F) from throttle trigger

(G). Remove another throttle rod end (H) from ball end (I) of throttle cable.

8. Remove throttle trigger (G) from throttle trigger post (J).

(F)

(H)

(I)

4-2 Reassembling handle and throttle control

(E)

(D)

(C)

(B)

(A)

1. Make sure ground lead (A) and stop lead (B) are put in fan case grooves (C), (D) and (E) as shown.

2. Install ground lead (A) and stop lead (B) to inner fan case ribs as shown.

NOTE: Either one of ground lead and stop lead can be upper.

24

HANDLE AND CONTROL SYSTEM PB-251

4-2 Reassembling handle and throttle control (continued)

(H)

(J)

(F)

(G)

3. Install throttle trigger (F) onto throttle trigger post

(G) as shown.

4. Hook the ball end (H) of throttle cable in the end of throttle rod. Then insert the other throttle rod end

(I) into the hole of throttle trigger. Make sure throttle rod is placed in throttle rod guide (J).

(K)

(I)

5. Install throttle cover (K).

(N)

(M)

(N)

(P)

(M)

(R) (Q)

(Q)

(R) (S) (O)

(L)

6. Install handle (L).

7. Hook flat coupler lead (M) from cylinder to the rib

(N).

8. Hook round coupler lead (O) from cylinder to the ribs (N, P, Q). Route it behind ignition switch.

9. Hook two leads (R, S) from ignition switch to the ribs (P, Q). Route it behind the ignition switch.

(T)

(S)

(O)

10. Connect flat coupler lead (M) from cylinder to terminal of ignition switch as shown. Hook lead to the rib (N) as shown.

11. Connect flat coupler lead (R) from ignition switch to terminal of ignition switch as shown. Hook lead to the rib (Q) as shown.

12. Connect round coupler leads (S) and (O). Put leads into the grooves (T) as shown.

NOTE: Keep each lead in correct position so that handle lid can be installed correctly.

13. Install handle lid, muffler cover and air cleaner cover.

PB-251

5 FUEL SYSTEM

FUEL SYSTEM

25

(A)

(B)

(C) (D)

(E)

(K)

(M)

(F)

(L)

(G)

(N)

(P)

(H)

( A ) Air cleaner cover

( B ) Air filter

( C ) Prevent plate

( D ) Air cleaner case

( E ) Throttle bracket

( F ) Carburetor

( G ) Intake insulator

( H ) Intake gasket

( I ) Fuel cap

( J ) Fuel tank

( K ) Fuel line grommet

( L ) Fuel lines

( M ) Fuel strainer

( N ) Tank vent

( O ) Tank vent grommet

( P ) Tank vent line

(I)

(O)

(J)

26

5-1 Cleaning air filter

5-2 Checking fuel cap and fuel strainer

(A)

FUEL SYSTEM PB-251

1. Close choke shutter and remove air cleaner cover and air filter.

2. Clean air cleaner cover and air filter with compressed air or wash air filter in a suitable cleaning solvent. Air filter should be dried completely after washing.

WARNING DANGER

Wear an eye protection when working with compressed air. Eye damage can occur from flying particles.

3. Replace air filter if heavily soiled or defective.

1. Remove fuel cap.

2. Check fuel cap for cracks and gasket (A) for cuts or damage. Replace defective parts as required.

3. Pull fuel strainer (B) from fuel tank using a wire hook and replace with a new one if it is blocked with dirt.

4. Reinstall fuel cap.

(B)

PB-251

5-3 Checking fuel tank and tank vent

FUEL SYSTEM

(A)

(D)

(B)

27

1. Disconnect black fuel line from carburetor and connect pressure tester 897803-30133 to fuel line by joint pipe V186-000020 (A).

2. Pinch tank vent line (B) with longnose pliers to block air passage. And then apply 0.5 kgf/cm 2 (7 psi) of pressure.

NOTE: Wrap the ends of longnose pliers with tape

(or cover with soft pipes as shown) to prevent damage to tank vent line.

3. The pressure should not drop. If the pressure drops, leakage may be occurring from fuel cap gasket, fuel tank, fuel lines, tank vent line or grommets. Check and replace them as required.

4. Release tank vent line. The pressure should stay at or above 0.1 kgf/cm 2 (1.5 psi). If pressure drops under 0.1 kgf/cm 2 (1.5 psi), tank vent or tank vent line is defective.

( j )

(F)

(J)

(E)

(H)

(G)

NOTE: Tank vent prevents a vacuum from forming in fuel tank when fuel in fuel tank is being consumed.

When pressure in fuel tank becomes too high, tank vent releases the pressure.

5. Remove tank vent (D) from tank vent line and connect pressure tester.

6. Apply pressure approximately 0.5 kgf/cm 2 (7 psi), make it sure the pressure should be stable in range of 0.1 - 0.4 kgf/cm 2 (1.4 - 6 psi).

7. If it is not in the range, gently clean tank vent with compressed air or replace with new one.

NOTE: Do not disassemble valves in tank vent assembly. Damage to valves will occur.

8. Remove cap (E) of tank vent, and clean sponge

(F).

9. Cut pipe 363024-04010 (G: 7x11x170mm) and

382011-01110 (H: 9x13x350) in approximately

30mm (1 1/4 in) length, and connect them to pressure tester as shown. Connect tank vent (J) without cap to pipe as shown.

10. Plug hole ( j ) by finger and apply pressure 0.2

kgf/cm 2 (3 psi). The pressure should be hold steady.

11. When the finger is removed from hole ( j ), tank vent should pass air freely without holding any pressure. If it does not, replace tank vent with new one.

28

FUEL SYSTEM

5-4 Replacing fuel line, tank vent line and grommet

(A)

(B)

PB-251

1. Disconnect fuel lines from carburetor.

2. Remove fuel line grommet (A) together with fuel lines. Fuel strainer can be directly pulled out through grommet hole.

3. Remove fuel strainer from fuel line.

4. For tank vent line replacement, remove air cleaner case and carburetor from cylinder.

5. Pull out tank vent grommet (B) from fuel tank, together with tank vent line.

6. Remove fuel lines and tank vent line from grommet. If pipe is defective, replace with a new one.

(A)

(E)

(e) (f)

(F)

(g)

(G)

(B)

7. Insert new line as follows:

(E) (F) (G)

Pipe

Black

(Strainer)

Length mm 175

(inch) (6.89)

Transparent

(Return)

85

(3.35)

Black

(Vent)

50

(1.97)

Distance (e) (f) (g)

mm 72~ 74 67~ 69 29~ 31

(inch) (2.84 ~ 2.91) (2.64 ~ 2.72) (1.14 ~ 1.22)

7. Install tank vent grommet (B) to fuel tank, together with tank vent line. Connect tank vent.

8. Connect fuel strainer to fuel line. And then install fuel line grommet (A) to fuel tank, together with fuel lines.

9. Install carburetor and air cleaner case to cylinder.

10. Connect fuel lines to carburetor.

PB-251 FUEL SYSTEM

29

5-5 Adjusting carburetor

GENERAL ADJUSTMENT RULES:

Before starting the unit for adjustment, check the following items.

a. Correct spark plug must be clean and properly gapped.

b. Air filter must be clean and properly installed.

c. Muffler exhaust port must be clear of carbon.

d. Fuel lines, tank vent and fuel strainer are in good condition and clear of debris.

e. Fuel is fresh ( > 89 octane :

FC/FD” 2 stroke oil.

RON+MON

2

) and properly mixed at 50 : 1 with “ISO L-EGD” or “JASO M345f. All blower pipes are installed for proper engine loading.

Start and run engine for 3 minutes alternating rpm between WOT for 50 seconds and idle for 10 seconds.

Adjust idle adjust screw to 3,000 +/- 200 rpm. If engine does not run correctly after this adjustment, proceed to the next steps.

IMPORTANT: After adjusting carburetor according to the next steps, the limiter plugs must be installed in idle and hi speed (H) mixture needles to comply with Emission regulation.

(A)

REQUIRED TOOLS & PARTS: Small screwdriver with 2.5 mm blade, P/N 990511-30017 electronic tachometer, P/N 91020 limiter plug tool, P/N P005-

001270 limiter plugs.

(D)

1. Remove limiter 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.

(B)

(2)Screw limiter plug tool counterclockwise 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.

(A)

(C)

(1)

(2)

(D)

(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.

(G)

(3)

(G)

(D)

Fig1

2. Turn H mixture needle (B) clockwise until lightly seated. And then turn H mixture needle counterclockwise 1 1/8 turns. Turn idle mixture needle (A) clockwise until lightly seated. And then turn idle mixture needle counterclockwise 5 3/8 turns.

3. Turn idle adjust screw (D) clockwise until its head touches boss (G) as shown Fig 1. Then turn idle adjust screw (D) counterclockwise 5 turns.

30

5-5 Adjusting carburetor (Continued)

(E)

(A)

FUEL SYSTEM

(D)

PB-251

NOTE : The initial carburetor settings for idle adjust screw, idle and H mixture needles are intended to start and run the engine before final carburetor adjustments are made to conform the unit to meet

Emission Regulations. Actual turns required for engine operation may vary.

4. Start engine and warm it up alternating rpm between WOT and idle every 10 seconds for 1 minute.

5. Adjust idle mixture needle (A) with 2.5 mm blade screwdriver (E) to reach maximum engine speed just before drop off.

6. Set idle speed to 3,500 rpm by turning idle adjust screw (D). Engine rpm should be stable at 3,500

+/- 10 rpm after idle adjust screw adjustment.

7. Turn idle mixture needle (A) counterclockwise to reduce idle speed 500 to 600 rpm in the range of

2,900 to 3,000 rpm.

NOTE: Engine speed must be allowed to stabilize a minimum of 20 seconds after each adjustment of idle mixture needle to assure accurate tachometer readings.

(F)

(B)

8. Adjust H mixture needle (B) and obtain maximum

WOT engine speed just before lean drop off using

2.5mm blade screwdriver.

9. Turn H mixture needle (B) counterclockwise to reduce WOT engine speed 10-20 rpm. Minimum

WOT engine speed after adjusting should be over

6,700 rpm.

10. Start engine, and verify engine idle speed ranges from 2,800 to 3,200 rpm, and WOT engine speed ranges from 6,700 to 7,200 rpm. When final adjustment is completed, the engine should idle, accelerate smoothly, and attain WOT per above specification.

11. After adjusting carburetor, insert and secure new plug(s) (F) P005-001270 deep in the needle holes per the Emission regulation using limiter plug tool

(C).

(C)

PB-251

5-6 Testing carburetor

(B)

(A)

FUEL SYSTEM

31

1. Remove air cleaner cover. Push purge bulb several times to fill and wet fuel pump circuit with fuel.

2. Pull off black fuel line (A) from carburetor and connect pressure tester 897803-30133 (C) to fuel inlet of carburetor.

(C)

3. Apply pressure to approx. 0.8 kgf/cm 2 (10 psi).

The pressure should remain over 0.5 kgf/cm 2 (7 psi).

4. If it drops below 0.5 kgf/cm 2 (7 psi), re-tighten pump cover and repeat the previous Step 3. If it still drops rapidly, proceed to Step 6 to locate the leak.

5. Apply pressure to 0.5 kgf/cm 2 (7 psi) and push purge bulb. Pressure should drop. If it does not drop, check metering lever height for too low of a setting

(accorfing to “5-6 Checkihg metering lever”), or inlet needle valve for sticking (according to “5-7

Checking inlet needle valve”).

6. Remove fuel return line (B) and throttle rod from carburetor, then remove carburetor from engine.

With pressure tester attached, submerge carburetor in suitable clean solvent and apply 0.5 kgf/cm 2

(7 psi) pressure to locate the leak.

7. If the air bubbles come out between pump body and carburetor body, check the pump diaphragm, pump gasket, and diaphragm seat of carburetor body. Refer to 5-5.

8. If air bubbles come out from carburetor bore, check inlet valve, metering lever spring and metering lever height. Refer to 5-6 and 5-7.

32

5-7 Checking crankcase pulse passage

FUEL SYSTEM PB-251

1. Remove carburetor and drop a little oil in pulse hole (A) on intake insulator.

2. Remove spark plug and pull starter grip several times. Oil should spit back from the hole.

3. If not, remove intake insulator and gasket from cylinder. Check gasket for misassembly or remove oil residue clogging pulse passsages in intake insulator and cylinder.

4. Install gasket, intake insulator and other remaining parts to cylinder.

(A)

5-8 Checking metering lever

1. Remove metering diaphragm cover, metering diaphragm and gasket.

2. Check metering lever height.

Metering lever height: 0.1 to 0.25 mm (0.004 to 0.010

in) lower than diaphragm.

3. If necessary, gently bend metering lever up or down to set the metering lever to proper position.

NOTE: When metering lever is:

Too high → Fuel flooding

Too low → Fuel starvation

PB-251

5-9 Checking inlet needle valve

(B)

(C)

(A)

5-10 Checking diaphragm and others

FUEL SYSTEM

33

1. Remove metering lever (A) and its pin. Remove spring (B) and inlet needle valve (C).

2. Inspect inlet needle valve if worn or sticky. Clean or replace as required.

NOTE: Causes of the fuel flooding from carburetor to cylinder are as follows:

- Improper assembling of metering lever and spring.

- Dirt between inlet needle valve and valve seat.

- Worn inlet needle valve tip.

3. Clean inlet needle valve seat.

4. Reassemble inlet needle valve, spring, metering lever and pin.

NOTE: Make sure that spring is seated in its hole at the chamber floor under dimple of metering lever, and that metering lever is holding inlet needle valve.

(E)

(B)

(C)

(D)

1. Check metering diaphragm (A) for hardening, distortion or pin hole. Replace it as required.

2. Remove pump body assembly (B) and pump diaphragm (C).

3. Check pump diaphragm and replace it if hardened or curled at the valve tabs.

4. Check metering and pump gaskets and replace if defective.

5. Check inlet screen (D) if blocked with dust. Remove and clean it or replace it if defective.

6. Check purge bulb (E) for crack, or fatigue. Replace it as required.

(A)

34

5-11 Replacing carburetor

FUEL SYSTEM

1. Remove carburetor.

PB-251

(E)

(A)

(B)

(C)

2. Rotate throttle valve (A) clockwise by finger, until swivel (B) touches boss (C).

(D)

3. Push ball end (D) of throttle cable to move the other throttle cable end (E) from swivel (B).

(B)

4. Remove throttle cable.

PB-251

5-11 Replacing carburetor (continued)

(G)

(K)

(L)

(G)

(F)

FUEL SYSTEM

35

(H)

(I)

(J)

5. Use 10mm spanner (F) and remove throttle bracket (G) and nut (H) from old carburator.

6. Install nut (H) into boss (I) of new carburetor (J).

7. Apply thread locking sealant (Loctite #242,

ThreeBond 1324 or equivarent) on threads (K, L) of throttle bracket (G).

NOTE: Throttle bracket has two different threads.

(K) is M7 thread for plastick boss (I). (L) is M6 thread for nut (H).

(M)

8. Screw in throttle bracket (G) into boss of carburetor with 10mm spanner. Screw in until distance

(M) becomes 2.4mm (0.1 inch).

(G)

(G)

(N)

(O)

9. Make sure groove (N) of throttle bracket (G) is pointing the corner (O) of carburetor body. If not, adjust throttle bracket direction according to the following instruction.

10. If groove of throttle bracket doesn’t reach the corner of carburetor, screw in throttle bracket clockwise and align groove to the corner of carbretor.

36

5-11 Replacing carburetor (continued)

FUEL SYSTEM PB-251

11. If groove of throttle bracket overrun the corner of carburetor, screw in throttle bracket clockwise and meet groove to the corner of carbretor.

NOTE: Do not turn the throttle bracket out counterclockwise, because throttle bracket may come loose over time.

(P) (Q)

12. Install throttle cable.

NOTE: Engage cable end (P) and swivel (Q).

(R)

(V)

(S)

(T)

13. Install carburetor to intake insulator on cylinder, together with prevent plate, air cleaner case and gaskets.

NOTE: While installing carburetor, hook the ball end

(R) of throttle wire by the end (S) of throttle rod.

Make sure throttle rod is placed in throttle rod guide

(T).

14. Connect fuel line (U) and fuel return line (V) to carburetor as shown.

(U)

PB-251

6 BLOWER SYSTEM

(A)

BLOWER SYSTEM

37

( A ) Fan case grid

( B ) Outer fan case

( C ) Fan

( D ) Inner fan case

( E ) Bolwer pipe fixture

(B)

(E)

(C)

(D)

38

6-1 Disassembling fan and fan case

BLOWER SYSTEM

(A)

PB-251

1. Remove blower pipes, blower pipe fixtures, air clener cover and handle lid.

2. Remove seven screws and remove outer fan case.

3. Remove spark plug cap and clean out dirt around spark plug. Remove spark plug.

4. Install piston stopper 897537-30130 (A) in spark plug hole by hand to stop crankshaft rotation.

NOTE: In order to keep combustion chamber clean, do not drop dust around the spark plug into the hole.

(C)

5. Remove bolt (B) with 13mm socket wrench, and remove fan (C) and washer (D).

6. Remove inner fan case from engine block.

(D)

6-2 Reassembling fan and fan case

(F)

(B)

(G)

(E)

1. Install inner fan case to engine block.

2. Install fan and washer (C, D in “6-1 Disassembling fan and fan case”), and tighten bolt (B in “6-1

Disassembling fan and fan case”) to fan hub (E).

IMPORTANT: Mate three pins (F) of fan hub with three holes (G) of fan.

3. Remove piston stopper from spark plug hole, and reinstall spark plug, spark plug cap and spark plug cap cover.

4. Install outer fan case.

6. Install handle lid, air cleaner case and blower pipe fixtures.

PB-251

7 ENGINE

(M)

(N)

(A)

(J)

ENGINE

39

(B)

(C)

(D)

(E)

(F)

( A ) Cylinder cover

(plastic)

( B ) Cylinder cover

(metal)

( C ) Cylinder

( D ) Cylinder gasket

( E ) Piston ring

( F ) Piston

( G ) Piston pin

( H ) Snap ring

( I ) Needle bearing

( J ) Circular washer

( K ) Ball bearing

( L ) Dowel pin

(M ) Oil seal

( N ) Crankcase

( O ) Crankshaft assembly

( P ) Crankcase gasket

(G)

(H)

(I)

(N)

(P)

(O)

(K)

(L)

(M)

40

7-1 Testing cylinder compression

ENGINE PB-251

NOTE: Test cylinder compression when engine is cold.

1. Set ignition switch to STOP position and remove spark plug.

2. Install compression gauge in cylinder spark plug hole as shown and pull starter several times to stabilize reading.

3. If pressure is lower than approx. 90psi, check cylinder bore, piston and piston ring if worn-out. (Refer to “1-2 Technical data” for standard compression pressure.)

4. If pressure is more than approx. 145psi, check cylinder combustion chamber and exhaust port, piston crown, and muffler for carbon deposits.

NOTE: Compression pressure varies with volume of compression gauge tip occupying cylinder combustion chamber. If gauge tip volume is considerably different from spark plug volume, it is recommended to measure and note compression pressures of brand-new engines as standard pressure in advance.

5. Remove compression gauge, then install spark plug and spark plug cap.

7-2 Cleaning cooling air passages

NOTE: Blocked pawl carrier fins (A), cylinder cooling fins or air intake will cause engine overheat and seizure.

1. Remove muffler cover and starter case.

2. Inspect pawl carrier fins (A). If blocked with leaves or other debris, clean as required.

(A)

PB-251

7-2 Cleaning cooling air passages (continued)

(C)

ENGINE

(B)

(D)

41

3. Remove spark plug cap and clean dirt around spark plug. Remove spark plug.

4. Install piston stopper 897537-30130 (D) in the spark plug hole by hand to stop crankshaft rotation.

5. Remove pawl carrier (B) counterclockwise with

6mm L hexagonal wrench 895615-10860.

6. Remove cylinder cover (C).

7. Inspect cylinder cooling fins for blockage with dirt or dust.

8. Clean air passage, with wooden stick or compressed air as required.

WARNING DANGER

Wear eye protection when working with compressed air. Eye damage can occur from flying particles.

9. Inspect crankcase air intakes (E). If blocked with leaves or other debris, clean as required.

(E)

7-3 Checking muffler and exhaust port

1. Remove muffler.

2. Inspect cylinder exhaust port and clean the port using wooden or plastic stick if carbon are found.

NOTE: When cleaning the port, always position piston at Top Dead Center (TDC) to prevent carbon from entering cylinder. Do not use metal tool and be careful not to scratch piston or cylinder.

42

7-3 Checking muffler and exhaust port (continued)

ENGINE

(A)

(B)

PB-251

3. Remove holders (B), gasket (A), and screen (C, if present) from muffler.

4. Remove carbon deposits from screen, muffler, and other component parts. If heavily deposited, replace with new parts as required.

5. Reinstall muffler together with new gasket and other removed parts.

(C)

7-4 Testing crankcase and cylinder sealings

(D)

(C)

(B)

(A)

1. Remove carburetor and muffler.

2. Close intake port and crankcase pulse passage using pressure plug 897826-16131 (A) and pressure plate 897827-16131 (B).

3. Close exhaust port with pressure plug 897826-

16131 (A) and install muffler.

4. Remove spark plug and install pressure connector 897835-16131 (C).

5. Connect pressure tester (D) to the connector and apply approx. 0.2 kgf/cm 2 (3 psi) of pressure.

NOTE: Do not exceed 0.5 kgf/cm 2 (7 psi), damage to oil seals will result.

6. Gauge should indicate constant pressure at minimum of 0.2 kgf/cm 2 (3 psi).

NOTE: An air leak down rate of 0.05 kgf/cm 2 (1 psi) per minute is acceptable until the minimum holding pressure of 0.2 kgf/cm 2 (3 psi) is attained.

7. If the reading drops, use soapy water to locate leakage. Leakage may occur from cylinder base, crankcase seam, or oil seal.

8. Remove plugs from exhaust port and intake port after this test, and reinstall all the removed parts in place.

PB-251

7-5 Replacing oil seal

(A)

(B)

ENGINE

43

1. Pry defective oil seal(s) from engine.

2. Lubricate a new oil seal on its circumference with lubricant and push it in using an oil seal tool

897726-16431 (A).

NOTE: Since oil seal on starter side should be located at 1 to 1.5 mm (0.04 to 0.06 in) deeper than the crankcase surface, always use the washer

363018-00310 (B) or similar size of the washer specified below, together with the oil seal tool.

Inner diameter : 12 mm (0.48 in)

Outer diameter : 19 to 22 mm (0.75 to 0.85 in)

Thickness : 1 to 1.5 mm (0.04 to 0.06 in)

NOTE: When installing oil seal, place it level to avoid being cocked in bore.

7-6 Checking cylinder

(A)

1. Remove cylinder from engine.

NOTE: When removing cylinder except for the purpose of replacing cylinder, leave ignition coil, carburetor and muffler assembled to avoid extra work.

NOTE: Gently tap cylinder with plastic mallet at carburetor and/or muffler sides of the cylinder head if it is difficult to remove.

2. Inspect cylinder combustion chamber (A). Clean with wooden or plastic scraper if carbon is deposited.

NOTE: Never use metal scraper in cylinder combustion chamber to avoid damage.

3. Replace cylinder with a new one if chrome plating is worn exposing cylinder base metal, peeled away or scored.

44

7-7 Checking piston and piston ring

(A)

ENGINE PB-251

(B)

1. Clean piston crown with fine sandpaper or wooden scraper as required.

2. After removing piston ring, clean piston ring groove using ring groove cleaning tool.

NOTE: Do not use square end of broken piston ring when cleaning piston ring groove, otherwise, piston ring groove might be damaged.

3. Check piston and piston rings for wear or heavy discoloration. Refer to 1-5 E, G and H. Replace as required.

4. Remove snap rings from piston and discard them.

5. Push the piston pin out from the piston.

NOTE: If the piston pin is tight, use piston pin tool

897702-30131 (A) with the adapter stamped “8” on an end and piston holder 897719-02830 (B).

6. Check piston pin and needle bearing for wear or discoloration. Replace as required.

7-8 Replacing needle bearing

(A)

(B)

(C)

N O T E : A l w a y s u s e n e e d l e b e a r i n g t o o l

897705-11520 to replace needle bearing on small end of connecting rod.

1. Put small end on the base (B) of needle bearing tool and fit needle bearing (A) into the hole of base.

2. Push needle bearing out from small end using smaller pusher (C).

(B)

(D) 3. Put small end of connecting rod on the base (B) aligning both holes of small end and the base.

4. Put new needle bearing on small end.

NOTE: Identification stamped side of needle bearing should face up.

5. Push needle bearing into the bottom using larger pusher (D).

PB-251

7-9 Disassembling crankcase

7-10 Replacing ball bearings

ENGINE

45

1. Remove three crankcase screws.

2. Hold crankcase and tap crankshaft end using plastic mallet to separate crankcase halves.

NOTE: To avoid crankcase damage, use 0.5kg (1 lb) plastic mallet and minimum force to drive it out.

3. Repeat Step 2 to remove crankshaft from another crankcase half.

4. Clean inside of crankcase halves if dirty. Replace as a set if damaged.

5. Inspect crankshaft for roughness (crankshaft runout), discoloration, or other damage. Replace it with new one as required.

1. Check ball bearings for smooth rotation.

If rough, replace it (them).

2. Pry oil seal from crankcase.

3. Remove ball bearings from crankcase halves using bearing tool set 897701-14732 as shown.

4. Coat bearing housing in crankcase with heat resistant grease.

5. Press new ball bearings into crankcase halves using ball bearing tool as shown.

NOTE: Preheat crankcase around bearing using floodlight or suitable heater for easier installation.

6. Check that ball bearing is seated and rotates smoothly.

7. Install new oil seal. (Refer to “7-5 Replacing oil seal”.)

46

7-11 Assembling crankshaft and crankcase

ENGINE

(A)

PB-251

1. Clean mating surface of each crankcase half.

2. Insert crankshaft starter end into starter side of crankcase half until properly seated. If hard to insert, preheat ball bearing using floodlight or suitable heater for easier installation.

3. Place new crankcase gasket (A) on starter side crankcase half.

4. Reassemble both crankcase halves together ensuring that dowel pins on crankcase half are properly seated in holes of the opposite crankcase half.

5. Tighten three bolts to secure crankcase halves together and check crankshaft rotation.

NOTE: The torque differences among three bolts should not exceed 20kgf•cm (17in•lbf).

6. Carefully remove excess portion of crankcase gasket (B) with sharp knife.

7-12 Installing piston

(B)

(A)

1. Lubricate needle bearing (A) with two-stroke oil.

2. Insert needle bearing (A) into small end of connecting rod.

3. Place piston over small end of connecting rod so that arrow mark (B) on piston points toward exhaust side.

4. Insert piston pin guide (C) stamped “8” through piston, washers (D) and needle bearing in connecting rod.

(D)

(C)

(G) (E)

(F)

5. Insert piston pin (E) in piston pushing out piston pin guide (C) using piston pin tool 897702-30131

(F).

NOTE: Piston holder 897719-02830 (G) is recommended for easier installation.

6. Install new snap rings to piston pin bore, and be sure that they are properly seated in the grooves.

PB-251

7-13 Installing piston ring and cylinder

(A)

ENGINE

(B)

47

1. Hold new cylinder gasket on cylinder base with

Loctite #222, ThreeBond 1324 or equivalent for easier installation of cylinder.

2. Install piston ring on piston ensuring that locating pin (A) is positioned between ring ends.

3. Apply oil to piston ring and cylinder internal wall.

(C)

4. Install cylinder over piston ensuring that exhaust side of cylinder is at arrow side (B) of piston.

NOTE: When installing piston, it is convenient to use piston holder 897719-02830 (C) for stabilizing piston.

NOTE: Do not twist cylinder while installing, otherwise, piston ring and/or cylinder wall may be damaged.

48

7-14 Installing engine to inner fan case

(A) (B)

(D)

ENGINE PB-251

(F)

(C)

1. Install flywheel and fan hub to crankshaft (reffer to “3-10 Checking flywheel and key”). Set pole shoe air gaps (reffer to “3-9 Setting pole shoe air gaps”).

2. Install pawl carrier spacer (A) and pawl carrier to engine (reffer to “2-5 Replacing starter pawl”).

3. Loosey install metal cylinder cover (B) and plastic cylinder cover (C).

4. Assemble stop lead grommet (D), high tension lead grommet (E) to metal engine cover as shown.

5. Assemble high tension lead (F) to plastic engine cover.

(E)

(B)

6. Tighten metal cylinder cover bolts (B) while pressing metal cylinder cover towards engine starter side as shown by the direction of the arrow.

NOTE: When tightening bolts, position ground lead terminal (G) against stopper (H) of cylinder cover as shown in illustration.

(G)

(H)

(I) (J)

(L)

(K)

7. Install engine to inner fan case, together with fuel tank.

NOTE: Install edge (I) of cylinder cover into groove

(J) of fan case. Put leads (K) in groove (L) of fan case.

NOTE: Fuel tank cannot be Installed after engine is installed.

PB-251 MAINTENANCE GUIDE

49

8-1 Service intervals

Check point

Screws, bolts, and nuts

Air filter

Service

Intervals

Reference

3 months 6 months

Daily or or

100 hours 300 hours

Inspect / Retighten / Replace

Clean 5-1

Inspect / Replace 5-1

Inspect / Replace 5-6, 5-10, 5-11

Inspect / Repair 5-2, 5-3 *

Carburetor

Fuel leaks

Fuel line

Choke system

Cooling system

Spark plug

Fuel strainer

Leads and connections

Fuel tank

Inspect / Repair

Inspect / Clean / Replace

Inspect / Clean

Clean / Regap

Inspect / Replace

Clean / Replace

Inspect / Repair

Clean inside.

5-4

7-2

3-3

3-3

5-2

3-6, 3-7, 4-2

Muffler and exhaust port Clean

Starter rope Inspect / Clean

7-3

2-1, 2-3, 2-4

Daily: Checking in every services.

IMPORTANT: Service intervals shown above are maximum. Actual use and your experience will determine the frequency of required maintenance.

* Inspect after every refuel.

50

8 MAINTENANCE GUIDE

8-2 Troubleshooting guide

TROUBLE

Engine does not crank.

Engine does not start.

Fuel leaks.

Idling is not stable.

Acceleration is poor.

Engine stalls at high speed.

Engine lacks power.

Engine overheats.

Engine misfires.

Engine / others are extremely noisy.

Fuel consumption is excessive.

Vibration is excessive.

Engine does not stop.

MAINTENANCE GUIDE

05

06

07

08

01

02

03

04

09

10

11

12

13

PB-251

CHECKING

Starter system

Rewind spring

Starter pawl / spring

Ignition system

Sparks

Spark plug

Spark plug cap / coil

Ignition switch

Ignition coil

Pole shoe air gaps

Flywheel

Flywheel key

REFERENCES Check first.

13 12 11 10 09 08 07 06 05 04 03 02 01

2-2

2-5

13 12 11 10 09 08 07 06 05 04 03 02 01

3-2

3-3

3-4

3-6, 3-7

3-5, 3-8

3-9

3-10

3-10

(Continued)

PB-251 MAINTENANCE GUIDE

51

8-2 Troubleshooting guide (Continued)

CHECKING

Fuel system / Carburetor

Air filter

Fuel cap / strainer

Fuel tank / vent / pipe

Carburetor adjustment

Carburetor leakage

Crankcase pulse passage

Carburetor metering lever

Carburetor inlet valve

Compression / Exhaust system

Cylinder compression

Cooling air passage

Muffler / Exhaust port

Crankcase / cylinder sealings

Cylinder

Piston / Piston ring

Crankshaft

Crankcase ball bearings

Blower

Fan

Fan case

REFERENCES

6-1

6-1

7-7

7-9

7-10

7-1

7-2

7-3

7-4

7-6

5-1

5-2

5-3, 5-4

5-5

5-6

5-7

5-8

5-9

Check first.

13 12 11 10 09 08 07 06 05 04 03 02 01

13 12 11 10 09 08 07 06 05 04 03 02 01

13 12 11 10 09 08 07 06 05 04 03 02 01

52

8-3 Disassembly chart

Air cleaner cover

(5-1)

Muffler cover

Air filter

(5-1)

MAINTENANCE GUIDE

Handle lid

(4-1)

Ignition switch

(3-7)

Handle

(4-1)

Throttle control

(4-1)

Outer fan case

(6-1)

Fan

(6-1)

Fuel tank

Carburetor

Inner fan case

(6-1)

Intake insulator

Muffler

Cylinder cover

Ignition coil

(3-8)

Cylinder

(7-6)

Fan hub

Flywheel

(3-10)

Piston ring

(7-7)

Piston

(7-7)

Oil seal, fan side

(7-5)

Crankcase

(7-9)

Crankshaft

(7-9)

Needle bearing

(7-8)

Ball bearings

(7-10)

Oil seal, starter side

(7-5)

Starter assembly

(2-1)

Pawl carrier

(2-5)

Engine cover

PB-251

PB-251

Adapter, piston pin tool 44, 46

Air filter 26, 49

Ball bearing, crankcase 45

Bearing tool 6, 45

Bolt (as special tool) 6, 20

Carburetor 33

Carburetor adjustment 29, 30

Carburetor pressure test 31

Coil resistance 16

Compression gauge 6, 40

Compression pressure 3, 40

Con-rod small end bore 5

Cooling air passage 40, 49

Crankcase 42, 45, 46

Crankcase / Cylinder sealings 42

Crankcase pulse passage 32

Crankshaft 45, 46

Crankshaft runout 5

Cylinder 42, 43, 47

Cylinder bore 5

Cylinder compression 40

Cylinder fins 40

Diaphragms, carburetor 33

Disassembly chart 52

Exhaust port 41, 49

Fan 38

Fan case 38

Fan hub 20, 38

Flanged nut (as special tool) 6, 20

Flywheel 19

Fuel cap 26, 49

Fuel lines 27, 28, 31, 49

Fuel strainer 26, 28, 49

Fuel tank 27, 49

Gasket, carburetor diaphragm 33

Gasket, crankcase 46

Gasket, fuel cap 26

Gasket, muffler 42

Grommet, fuel line 28

Grommet, tank vent 28

H mixture needle 3, 29, 30

INDEX

High tension lead 16

Idle mixture needle 3, 29, 30

Idle adjust screw 3, 29, 30

Idling speed 3, 29, 30

Ignition coil 19

Ignition switch 17

Ignition timing 3

Inlet needle valve 33

Inlet screen 33

Intake insulator 32

Key, flywheel 20

L-hex wrench 6, 12

Lead, ignition switch 17, 49

Lead terminal 17

Limiter plug 29

Limiter plug tool 6, 29

Locating pin, piston 47

Metering lever 32

Metering lever height 3, 32

Minimum secondary voltage 3

Module air gap tool 6, 19

Muffler 41, 49

Needle bearing 44, 46

Needle bearing tool 6, 44

Oil seal, crankcase 43, 45

Oil seal tool 6, 43

Pawl carrier 12

Piston 44, 46

Piston holder 6, 44, 46, 47

Piston outer diameter 5

Piston pin bore 5

Piston pin outer diameter 5

Piston pin tool 6, 44, 46, 49

Piston ring 44, 47

Piston ring end gap 5

Piston ring groove 5, 40

Piston ring side clearance 5

Piston ring width 5

Piston stopper 6, 11, 12, 20, 38, 41

Pole shoe air gaps 3, 19

Pressure connector 6, 42

53

Pressure plate 6, 42

Pressure plug 6, 42

Pressure tester 6, 27, 31, 42

Primary coil resistance 3

Purge bulb 31, 33

Rewind spring 9

Rope guide 10

Rope tension 11

Secondary coil resistance 3, 16

Service intervals 49

Service limits 5

Spark plug 15, 49

Spark plug cap 16

Spark plug cap coil 16

Spark plug gap 3, 15

Spark test 15

Spark tester 6, 15

Special tools 6

Specifications 2

Starter center post 10

Starter drum 8, 10, 11

Starter grip 8, 10, 11

Starter pawl 11, 12

Starter rope 8, 10, 11, 49

Tachometer 6, 29

Tank vent 27, 28

Tank vent line 27, 28

Technical data 3

Test pressure, carburetor 3

Thread locking sealant 4, 10, 20, 35,

47

Throttle bracket 35, 36

Throttle cable 23, 24, 34

Throttle cover 22, 24

Throttle rod 23, 24

Throttle trigger 23, 24

Throttle valve 34

Torque limits 4

Troubleshooting guide 50, 51

Troubleshooting guide, ignition 14

Washer (as special tool) 6, 43

TOKYO JAPAN

Printed in Japan

0705