Echo PB-251 Service Manual Download Page 1

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Ord. No. 403-16

Summary of Contents for PB-251

Page 2: ...estings 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 prod...

Page 3: ...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 C...

Page 4: ...scharge 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 Start...

Page 5: ...tance k 2 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...

Page 6: ...80 7 8 60 70 Muffler cover M5 30 45 3 4 5 25 40 Others Outer fancase M5 20 40 2 4 17 35 Fan M8 140 160 14 16 120 140 Fan hub M8 160 200 16 20 140 175 Regular bolt nut M3 6 10 0 6 1 0 5 9 and screw M4...

Page 7: ...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 en...

Page 8: ...nstalling 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...

Page 9: ...nd 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 Remov...

Page 10: ...sion 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...

Page 11: ...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 lith...

Page 12: ...nother 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...

Page 13: ...ckwise 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 starte...

Page 14: ...pring 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 w...

Page 15: ...h 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 l...

Page 16: ...ition 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...

Page 17: ...sition 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 yel...

Page 18: ...rk 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 tens...

Page 19: ...ite 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 Replacin...

Page 20: ...nition 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...

Page 21: ...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 agai...

Page 22: ...langed 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...

Page 23: ...D CONTROL SYSTEM PB 251 21 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 E G C D...

Page 24: ...ontrol 1 Remove air cleaner cover and muffler cover 2 Remove screw A M5x20 in order to remove handle lid 3 Remove screw B M5x25 and screw C M5x20 Remove handle lid 4 Disconnect couplers D 5 Pull out l...

Page 25: ...e 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 1 Make sure ground lead A and stop lead B are put in fan case g...

Page 26: ...pler 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 10 Connect flat coupler lead M...

Page 27: ...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...

Page 28: ...er 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 5 2 Checking fuel cap a...

Page 29: ...n 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...

Page 30: ...vent line 6 Remove fuel lines and tank vent line from grom met If pipe is defective replace with a new one 7 Insert new line as follows E F G Trans Pipe Black parent Black Strainer Return Vent Length...

Page 31: ...gulation 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 1 Remove limiter plugs from idle mixt...

Page 32: ...nterclockwise 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...

Page 33: ...ush 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 in let needle valve for sticking according to 5...

Page 34: ...TE When metering lever is Too high Fuel flooding Too low Fuel starvation 5 7 Checking crankcase pulse passage 1 Remove carburetor and drop a little oil in pulse hole A on intake insulator 2 Remove spa...

Page 35: ...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 5 10 Checking d...

Page 36: ...ng carburetor 1 Remove carburetor 2 Rotate throttle valve A clockwise by finger until swivel B touches boss C 3 Push ball end D of throttle cable to move the other throttle cable end E from swivel B 4...

Page 37: ...o different threads K is M7 thread for plastick boss I L is M6 thread for nut H 8 Screw in throttle bracket G into boss of carbu retor with 10mm spanner Screw in until distance M becomes 2 4mm 0 1 inc...

Page 38: ...because throttle bracket may come loose over time 12 Install throttle cable NOTE Engage cable end P and swivel Q 13 Install carburetor to intake insulator on cylinder together with prevent plate air c...

Page 39: ...PB 251 BLOWER SYSTEM 37 6 BLOWER SYSTEM A Fan case grid B Outer fan case C Fan D Inner fan case E Bolwer pipe fixture B A E C D...

Page 40: ...e spark plug into the hole 5 Remove bolt B with 13mm socket wrench and remove fan C and washer D 6 Remove inner fan case from engine block 6 2 Reassembling fan and fan case 1 Install inner fan case to...

Page 41: ...inder 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 assembl...

Page 42: ...chamber and exhaust port pis ton crown and muffler for carbon deposits NOTE Compression pressure varies with volume of compression gauge tip occupying cylinder com bustion chamber If gauge tip volume...

Page 43: ...air passage with wooden stick or com pressed air as required WARNING DANGER Wear eye protection when working with com pressed air Eye damage can occur from flying particles 9 Inspect crankcase air int...

Page 44: ...ith pressure plug 897826 16131 A and install muffler 4 Remove spark plug and install pressure connec tor 897835 16131 C 5 Connect pressure tester D to the connector and apply approx 0 2 kgf cm2 3 psi...

Page 45: ...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 1 Remove cylinder from engine NOTE When removing cylinder except for the pur pose o...

Page 46: ...ght 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 Rep...

Page 47: ...runout discoloration or other damage Replace it with new one as required 7 10 Replacing ball bearings 1 Check ball bearings for smooth rotation If rough replace it them 2 Pry oil seal from crankcase...

Page 48: ...ion 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 1 Lubricate needle...

Page 49: ...ing that locating pin A is positioned between ring ends 3 Apply oil to piston ring and cylinder internal wall 4 Install cylinder over piston ensuring that exhaust side of cylinder is at arrow side B o...

Page 50: ...ion lead grommet E to metal engine cover as shown 5 Assemble high tension lead F to plastic engine cover 6 Tighten metal cylinder cover bolts B while press ing metal cylinder cover towards engine star...

Page 51: ...ne Inspect Repair 5 4 Choke system Inspect Clean Replace Cooling system Inspect Clean 7 2 Spark plug Clean Regap 3 3 Inspect Replace 3 3 Fuel strainer Clean Replace 5 2 Leads and connections Inspect R...

Page 52: ...rheats Engine misfires Engine others are extremely noisy Fuel consumption is excessive Vibration is excessive Engine does not stop CHECKING Starter system Starter pawl spring Rewind spring Ignition sy...

Page 53: ...5 8 Carburetor inlet valve 5 9 Cooling air passage 7 2 Muffler Exhaust port 7 3 Cylinder compression 7 1 CHECKING 13 12 11 10 09 08 07 06 05 04 03 02 01 Compression Exhaust system 13 12 11 10 09 08 0...

Page 54: ...etor Fan hub Fuel tank Engine cover Throttle control 4 1 Air filter 5 1 Pawl carrier 2 5 Fan 6 1 Handle 4 1 Ignition switch 3 7 Starter assembly 2 1 Outer fan case 6 1 Handle lid 4 1 Muffler cover Air...

Page 55: ...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...

Page 56: ...TOKYO JAPAN Printed in Japan 0705...

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