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2016-11-23
User Manual: Redmax Redmax-Gz25N-Workshop-Manual-822458
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S4810-0006 R Workshop Manual STRATO CHARGED ENGINE GZ25N Applicable Model Name: 1. Brushcutters BCZ2500S/BCZ2500SU 2. Long Reach Trimmer LRTZ2500 3. Short Reach Trimmer SRTZ2500 4. Pole Saw PSZ2500 5. Reciprocator SGCZ2500S 6. Sweeper RMSZ2500 7. Hand Held Edger HEZ2500S 8. Split Boom Trimmer : EXZ2500S July 2000 CONTENTS BRUSHCUTTERS BCZ2500S/BCZ2500SU 1. OUTLINE OF STRATO-CHARGED ENGINE ................................. 2 1-1 1-2 Special Features ................................................................................................................................. 2 Principle of Operation ......................................................................................................................... 3 1-3 Construction (Developed Drawing) ..................................................................................................... 4 2. SPECIFICATIONS AND TECHNICAL DATA .................................. 5 3. OUTLINE DRAWING ...................................................................... 6 4. MAINTENANCE SPECIFICATIONS ............................................... 7 4-1 Engine Block ....................................................................................................................................... 7 4-2 4-3 Carburetor .......................................................................................................................................... 8 Ignition System ................................................................................................................................... 8 4-4 4-5 Fastening Specifications ...................................................................................................................... 8 Sealant and Lubricant Specifications .................................................................................................. 8 5. SPECIAL TOOLS ............................................................................ 9 6. SERVICE GUIDE .......................................................................... 10 6-1 6-2 GENERAL PRECAUTIONS .............................................................................................................. 10 Removing of Clunch Shoe ............................................................................................................... 11 6-3 6-4 Mounting of Clutch Shoe ................................................................................................................... 11 Removing of Rotor ............................................................................................................................ 11 6-5 6-6 Removing Recoil Pulley .................................................................................................................... 12 Assembling of lgnition Coil ................................................................................................................ 12 6-7 6-8 Installing of Spark Plug .................................................................................................................... 12 Laying of Switch Cable .................................................................................................................... 13 6-9 Fitting of Plug Cap ............................................................................................................................ 13 6-10 Removing Piston Pin ......................................................................................................................... 13 6-11 Installing of Piston 14 6-12 Assembling of Piston Pin Circlip ........................................................................................................ 14 6-13 Direction of Setting Cylinder Gasket ................................................................................................. 14 6-14 Positioning of Lead Air Intake Tube .................................................................................................... 15 6-15 Assembling of Cylinder Plate ............................................................................................................. 15 6-16 Setting of Insulator Gasket ................................................................................................................. 15 6-17 Mounting of Reed Valve ..................................................................................................................... 16 6-18 Removal of Clutch Drum .................................................................................................................... 16 6-19 Assembling Cluch Drum .................................................................................................................... 17 7. CARBURETOR ............................................................................. 18 7-1 Construction ..................................................................................................................................... 18 7-2 7-3 Function and Operation of Throttle Valve .......................................................................................... 18 Specifications .................................................................................................................................... 19 7-4 Composition and Inspection .............................................................................................................. 20 8. TROUBLE SHOOTING ................................................................. 21 8-1 Engine does not start ........................................................................................................................ 21 8-2 8-3 Stalled during Operation ................................................................................................................... 21 Engine cannot be stopped ................................................................................................................ 22 8-4 Lack of output power or unstable revolution ..................................................................................... 22 3 1. OUTLINE OF STRATO-CHARGED ENGINE STRATO CHARGED ENGINE GZ25N 1-1 Special Features Unlike the conventional 2-stroke engine scavenging system, the Strato-charged Engine scavenges burnt gas by the stratified lead air scavenging method. By creating a stratified air layer between burnt gas and the air-fuel mixture, this system significantly reduces exhaust of unburned air-fuel mixture. Difference to the conventional 2-stroke engine is its very simple construction applying a new carburetor for independent intake of the air and the air-fuel mixture, an insulator, lead air intake tubes, and reed valves, etc. By the stratified lead air scavenging system, the Strato-charged Engine reduces unburned air-fuel mixture exhaust to about 1/3 of the conventional 2-stroke engine level. Lead Air Intake Tube (each side) Insulator By optimizing the combustion chamber design, ignition plug position, and ignition timing, lean burn operation became possible. By combining with the stratified lead air scavenging system, pollutant contained in the exhaust was reduced and fuel consumption was reduced by 30% without reducing the power. Reed Valve (each side) Unit : g/HP•h (g/kwh) 400 (544) 280 (381) 171.2 (232) 139.1 (189) 54 (73) 49.5 (67) THC + NOx 5.3 (7.2) Current Engine 1.5 (2.0) CO PM 1.0 (1.3) Tier 2 regulation Strato-Changed Engine Carburetor As the catalytic converter is not applied, exhaust gas temperature increase due to the catalytic reactive heat does not occur so that the engine heat load does not increase. Therefore, same level of durability and reliability with the conventional engines are assured. A large size silencer and a muffler were employed and the noise level was reduced by 5 dB(A) compared to the conventional 2-stroke engines. 2 1. OUTLINE OF STRATO-CHARGED ENGINE STRATO CHARGED ENGINE GZ25N 1-2 Principle of Operation Major difference of the Strato-charged Engine to the conventional 2-stroke engine is that as illustrated on the following drawing, there are lead air intake tubes which are connected to the scavenging port via reed valves. As piston proceeds to downstroke after the top dead center, a scavenging port starts to open and lead air in the scavenging port moves into the cylinder earlier than the air-fuel mixture. Due to crankcase depression during the piston upstroke (intake stroke) to the top dead centre, air-fuel mixture is charged to the crankcase and lead air is charged to the scavenging ports though the reed valves. As piston proceeds to upstroke after the bottom dead center, burnt gas in the cylinder is pushed out through the exhaust port by lead air. Therefore, direct exhaust of air-fuel mixture is almost non. Lead Air Burnt Gas Burnt Gas Air Reed Valve Air-Fuel Mixture Exhaust Port Scavenging Port Air-Fuel Mixture Exhaust Port Lead Air Crankcase Air-Fuel Mixture Reed Valve Assy Lead Air Intake Tube Lead Air Air Scavenging Port Air-Fuel Mixture Carburetor Air-Fuel Mixture 3 1. OUTLINE OF STRATO-CHARGED ENGINE STRATO CHARGED ENGINE GZ25N 1-3 Construction (Developed Drawing) Parts in the frames are exclusively designed for the Strato-charged Engine. • Reciprocator SGCZ2500S Spark Plug Reed Valve Cylinder Lead Air Intake Tube Carburetor Reed Valve Insulator Lead Air Intake Tube • Brushcutters BCZ2500S/BCZ2500SU • Long Reach Trimmer LRTZ2500 • Short Reach Trimmer SRTZ2500 • Pole Saw PSZ2500 • Sweeper RMSZ2500 • Hand Held Edger HEZ2500S • Split Boom Trimmer : EXZ2500S 4 2. SPECIFICATIONS AND TECHNICAL DATA Item Unit STRATO CHARGED ENGINEGZ25N Specifications Engine GZ25N Engine Type Air cooled 2-stroke single cylinder piston valve gasoline engine Cylinder Bore x Stroke Displacement mm (in.) ø34 x 28 (1.339 x 1.102) cc (cu.in.) 25.4 (1.6) Effective Compression Ratio 8.0 Mixture of 87 octane or above unleaded gasoline and RedMax 2-cycle engine oil (ratio 50 :1) or quality oil for air cooled 2-cycle engines (ratio 32:1). Fuel Carburetor Remarks Type Use JASO FC or ISO EDG grade 2-cycle engine oil. Diaphragm Rotary valve Model Walbro WYA-1B Starting Method Recoil starter Ignition System CDI with automatic timing advance system. °/ rpm Ignition Timing 35 / 7000 Spark Plug NGK CMR7A Stopping Method Primary coil short-circuiting Cooling System Forced Air Cooling Air Cleaner Dry Type Output Axle Rotation Direction Counterclockwise Clutch Type Automatic Centrifugal Clutch (Sintered Clutch Shoe) Overall Size Engine GZ25N for Engine GZ25N2 for exept SGCZ2500S SGCZ2500S Length mm (in.) 271 (10.67) 188 (7.40) Width mm (in.) 223 (8.78) 223 (8.78) Height mm (in.) 248（9.76） 248（9.76） Dry Weight kg (lbs.) 3.1（6.8） 2.8（6.2） Fuel tank Capacity lit. (fl,oz) 0.65（22.0） Operating Speed rpm Idling Speed rpm 3000 ±200 Clutch Engagement Speed rpm 4000 ±200 No-Load Max Speed rpm 10000 Max Output HP(kW) / rpm 1.2 (0.9) / 7500 Max Torque kg•m(in.lbs) / rpm 0.12 (10.4) / 6500 g/HP.h(g/kW.h) 330 (449) Full Load Fuel Consumption (View from PTO) 6000 5 10000 With Standard Head 3. OUTLINE DRAWING STRATO CHARGED ENGINEGZ25N Unit : mm (in.) Engine Cover Carburetor Muffler Air Cleane Fuel Cap Fuel Tank Tank Guard 122 (4.80) 223 (8.78) Plug Cap Fan Cover Recoil Starter 113 (4.45) 113 (4.45) 248 (9.76) 248 (9.76) Fan Cover 7.85 (0.31) 168 (6.61) 238 (9.36) 85 (3.35) 155 (6.10) 271 (10.67) 188 (7.40) GZ25N for BCZ2500S, BCZ2500SU, LRTZ2500, SRTZ2500, PSZ2500, RMSZ2500, HEZ2500S and EXZ2500S. GZ25N2 for SGCZ2500S. 6 4. MAINTENANCE SPECIFICATIONS STRATO CHARGED ENGINEGZ25N 4-1 Engine Block Measuring Instrument Maintenance Item Standard Limit Compression kg/cm2 (psi) 8.7(124) 5.5(78) Compression Gauge Bore mm(in.) ø34(1.339) Peel off of plating or expose of base met Cylinder Gauge Piston dia. mm(in.) ø33.96(1.3370) ø33.975(1.3376) ø33.86(1.3331) Micrometer Piston Ring Groove Width mm(in.) 1.2(0.047) 1.3(0.051) Thickness Gauge Piston Pin Hole Bore mm(in.) ø8(0.3150) ø8.04(0.3165) Cylinder Gauge Clearance between Piston & Cylinder mm(in.) 0.025(0.0010) 0.065(0.0026) 0.15(0.0059) Micrometer / Cylinder Gauge Clearance between Groove and Piston Ring mm(in.) 0.04 (0.0016) 0.08(0.0031) 0.1(0.0039) Thickness Gauge Fitting between Piston Pin & Piston Pin Hole mm(in.) 0.005T(0.00020T) 0.011L(0.00043L) 0.05L(0.0020L) Micrometer / Cylinder Gauge End Gap mm(in.) 0.1(0.0038) 0.3(0.0118 0.5(0.0197) Thickness Gauge 1.2(0.0472) 1.1(0.0433) Micrometer ø8(0.315) ø7.98(0.314) Micrometer ø11(0.433) ø11.05(0.435) Cylinder Gauge Clearance between Small End Piston Pin & Needle Bearing mm(in.) 0 0.021(0.0008) 0.045(0.0018) Micrometer / Cylinder Gauge Clearance between Large End Crank Pin & Needle Bearing mm(in.) 0.005(0.0002) 0.028(0.0011) 0.05(0.0020) Micrometer / Cylinder Gauge – 0.15/100 Mandrel Dial Gauge Diameter at Main Bearing (MAG, PTO) mm(in.) ø12(0.4724) ø11.97(0.4713) Micrometer Diameter at Oil Seal (MAG, PTO) mm(in.) ø12(0.472) ø11.09(0.469) Micrometer Diameter at Clutch Drum mm(in.) Bearing ( PTO) ø12(0.4724) ø11.97(0.4713) Micrometer – 0.07(0.028) 22 21.9 – 0.5(0.020) – Flutter, irregular noise generated ø12 (0.472) ø12.05(0.474) Cylinder Gauge ø54(2.126) ø54.6(2.150) Vernia Calipers Remarks Cylinder Piston At right angle to piston pin. Piston Ring Width mm(in.) Measure at cylinder skirt. Piston Pin Diameter mm(in.) No stepwear is allowed Connecting Rod Small End Bore mm(in.) Parallelness of Large/Small End Bores mm(in.) Crankshaft mm(in.) Eccentricity Width between crank webs Axial Play mm(in.) mm(in.) Main Bearing (Ball Bearing) 22.1 Dial Gauge / Adjust or exchange Centre Support Micrometer Thickness Gauge Clutch Drum Bore at Bearing Bore at Drum mm(in.) mm(in.) 7 4. MAINTENANCE SPECIFICATIONS STRATO CHARGED ENGINEGZ25N 4-2 Carburetor Carburetor WYA-1B Metering Lever set. mm.(in.) Inlet valve opening pressure. kg/cm2(p.s.i) Inlet valve reseating pressure. kg/cm2(p.s.i) Measuring instrument Limit Standards Maintenance Item ±0.16 (±0.006) ±0.5 (±7.1) ±0.5 (±7.1) 1.5 (0.059) 1.5 (21.3) 0.9 (12.8) Remarks Vanier Leak Tester Leak Tester 4-3 Ignition System Standards Maintenance Item Measuring instrument Limit Remarks Electric parts Spark plug air gap. mm.(in.) Ignition coil air gap. mm.(in.) 0.6 (0.025 0.7 0.028) 0.3 (0.012) 0.7 (0.028) Vanier 0.4 (0.016) Air gap gauge Ibnition coil resistance Primary side Ohm Secondary side Ohm 2300 Volt Meter Reading between primary terminal and iron core. 1100 Volt Meter Reading between high tension terminal and iron core. 4-4 Fastening Specifications Unit : kg.cm(in.lbs) Fixing torque Screw Size Fixing Components Standard fix torque Carburetor Fix Bol Insulator Fix Bolt Clutch Rotor Fix Nut Cylinder Fix Bolt Crankcase Fix Bolt Grass Guard Fix Bolt Spark Plug Muffler Fix Bolt Engine Cover Fix Bolt Fan Cover Fix Bolt Ignition Coil Fix Bol Recoil Starter Fix Bolt Recoil Pulley Fuel Tank Fix Bolt Common fixing torque Tapping Screw Target M5 (P=0.8) M5 (P=0.8) M5 (P=1.0) M8 (P=1.0) M5 (P=0.8) M5 (P=0.8) M5 (P=0.8) M10 (P=1.0) M5 (P=0.8) M5 (P=0.8) M5 (P=0.8) M4 (P=0.7) M5 (P=0.8) M8 (P=1.25) 38(33) 45(39) 65(56) 130(112) 70(61) 65(56) 38(33) 110(96) 90(78) 38(33) 38(33) 33(29) 38(33) 90(78) M5 (P=0.8) 38(33) Tolerance 30(26) 40(35) 50(43) 100(87) 60(52) 50(43) 30(26) 100(87) 70(61) 30(26) 30(26) 25(22) 30(26) 80(69) 30(26) TP4.3 10 (9) 7(6) TP5.4 25(22) 20(17) Screw Lock Agent 45(39) 55(48) 80(69) 150(130) 80(69) 80(69) 45(39) 120(104) 100(87) 45(39) 45(39) 40(35) 45(39) 100(87) 45(39) 15(13) 30(26) 4-5 Sealant and Lubricant Specifications Recoil Starter: AREA Recoil spring Reel center hub Engine Block: MATERIAL TO BE APPLIED AREA Grease Grease Oil seal lip Piston sliding area Main bearing Piston pin bearing Crank pin bearing Clutch: AREA Sliding portion of screw. MATERIAL TO BE APPLIED Grease 8 MATERIAL TO BE APPLIED Grease 2-cycle oil 2-cycle oil 2-cycle oil 2-cycle oil 5. SPECIAL TOOLS Part name 1 Puller Assy STRATO CHARGED ENGINEGZ25N Part No. External appearance Usage 2890-96100 To remove rotor. 2 Piston Stopper 4810-96220 To hold crankshaft when disassembling / assembling clutch and rotor. 3 Rod Assy 1101-96220 To remove / install piston pin. 4 Air Gap Gauge 3350-96240 To set ignition coil. 5 Hex Wrench 3304-97611 For socket screw of Hex.3mm,4mm and 5mm. 6 Puller 4500-96100 To remove / install recoil pulley 7 Snap Ring Pliers 5500-96110 To remove snap ring. 8 Drum Remover 5500-96120 To remove clutch drum. 9 Snap Ring Guide 5500-96130 To install clutch drum. 10 Snap Ring Push Guide 5500-96140 To install clutch drum. 9 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-1 GENERAL PRECAUTIONS ■ Before beginning repair work Check each system thoroughly before beginning repair work. Inspect from the point where it is simplest and easiest for trouble to occur. Step-by-step inspection in the following order is recommended. Ignition system: From electric output(spark plug) to electric input(ignition coil). Fuel system : From fuel input(fuel cap/air vent) to output(carburetor). ■ Precautions before disassembly ■ Assembly precautions Before performing disassembly operations, be sure to drain all the fuel. Remove all dirt and dust Assembly sequence is reverse of disassembly. Use new cleaning oil in the assembly and wash each part while keeping the assembly sequence in mind. from each part. This is to prevent dirt from becoming attached to the important locations. Tool usage Use the indicated tools correctly to avoid damaging parts. Note: Do not use gasoline or oil to clean vibration damping rubber. Only remove the parts that are necessary for adjustment or repair, except when disassembling for an overhaul. Verify the function of all disassembled parts or re placement parts for assembly. During disassembly, try to memorize the location and way each part is attached to avoid errors during assembly. Label the parts if necessary. Adequately lubricate any revolving or rubbing parts before assembly. Pay attention to small parts during disassembly and check carefully for damage. Always use new or complete gaskets. (As a general rule, always use new parts for the reassembly.) Be careful when handling gaskets and oil seals as they can be damaged easily. Be sure to align all assembly marks. Be careful not to tighten screws or bolts excessively during assembly as they may be damaged. Be especially careful not to lose parts that have been removed. Arrange the removed parts in a pattern that approximates their actual position to prevent loss or error. Note: Consider the assembly sequence when cleaning the parts and wash the important parts first. It is important to discriminate between the main and sub-assembly steps. 1. Always use the correct tool for the particular screw, bolt, nut or other part. 2. When there are a number of securing screws or bolts for a part, tighten them equally in an alternating sequence. 3. Tighten the nuts and bolts to the specified torque. 4. Use Loctite#81666 to reform damaged threads in plastic parts. 10 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-2 Removing of Clunch Shoe Remove the housing and plug cap. Remove the spark plug and fit the stopper (481096220) into the plug hole. Stopper Remove clutch bolts (14mm Hex.) . Clutch Bolt (14mm Hex.) 6-3 Mounting of Clutch Shoe Apply grease into the holes on the clutch shoe before mounting the clutch. Grease : Molybdenum grease Clutch bolt fixing torque:50 80kg.cm(43-69in.lbs） Grease Clutch Shoe Caution: Care for orientation of the wave washers and clutch shoe. Arrow marks on the upper surface Clutch Shoe Wave Washer 6-4 Removing of Rotor Remove the rotor nut (12mm Hex.). Rotor Nut Remove the rotor using the puller assy (289096100). Apply 8mm puller bolts. 17mm Hex. Rotor Puller bolts Puller 11 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-5 Removing Recoil Pulley Remove the recoil starter and the spark plug. Insert the stopper (4810-96220) to the plug hole. Engage the puller (4500-96100) to 2 holes on the pulley and pull out the pulley. Pulley Puller Note: Pulley screw is right turn screw. 6-6 Assembling of lgnition Coil Insert the gauge (3350-96240) in between the rotor magnet metal and the coil. Tighten screws while pressing the coil against the rotor. Wrench Gap specification 0.3 0.4mm(0.012 0.016in.) Gauge Ignition coil 6-7 Installing of Spark Plug The spark plug nut is 16mm hex. so that conventional plug wrench (19mm) cannot be used. Make sure to use the custom plug wrench. 16mm Important: Fixing the spark plug using other tools than the custom plug wrench may apply over torque and end up with damages of threads on the cylinder. 12 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-8 Laying of Switch Cable Fit the lead wires with the clips on the side of the coil. Confirm that they do not touch with the rotor. Red Coil Black Clip 6-9 Fitting of Plug Cap Insert the guide of the plug cap into the engine cover securely. Plug cap guide Engine Cover Caution: Check that the plug cap is not deteriorated, stiffened, nor has cracks. Also check that there is no play after fitting the cap. 6-10 Removing Piston Pin Remove snap rings from both sides of the piston pin. Rod Assy Piston Engage the rod assy (1101-96220) to the piston pin and gently tap with a plastic hammer to push out the pin. Plastic Hammer Caution: Hard hammering may damage the big end of the connecting rod. 13 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-11 Installing of Piston Make sure to point the arrow mark on the piston to the exhaust side. Allow mark Exhaust side 6-12 Assembling of Piston Pin Circlip Fit the circlip in the groove so as to face the end gap below. Caution: Deformed circlip may come off during engine Piston operation and damage the engine. Circlip End Gap 6-13 Direction of Setting Cylinder Gasket Set an arrow mark (punched out) on the cylinder gasket toward the fan. Cylinder Gasket Caution: An oppositely set gasket will touch with the insulator, and makes a gap between the muffler. Therefore, the cooling air to the cylinder is leaked toward the tank and the cooling performance is reduced. Arrow Mark 14 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-14 Positioning of Lead Air Intake Tube The lead air intake tube has cast marking of either F or S . S is for the starter end, and F for the fan end. Assembling position shall not be mixed up. Marks Caution: Oppositely assembled tubes will cause a sealing failure. Before assembling the tubes, check for deterioration or cracks and change with new ones if necessary. Lead air intake tube 6-15 Assembling of Cylinder Plate A notch on the cylinder plate is to lay the high tension cable. Set the cylinder plate with the notch at the muffler side. Muffler side Notch Cylinder Plate 6-16 Setting of Insulator Gasket Set the insulator gasket under the engine cover with care for not turning it up by the engine cover. Insulator Gasket 15 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-17 Mounting of Reed Valve Check that there is no foreign matter inside the valve case. Max. 0.2mm Important: Check the gap between the valve case and the reed Reed Valve valve. Replace with new valve if the gap is larger than 0.2mm (0.008in.), or the valve is distorted. Screw lock agent shall be applied to the reed valve and the stopper fixing screw. The reed valve case has a marking either S or F . S is for the starter side, and F for the fan side. Assembling position shall not be mixed up. 6-18 Removal of Clutch Drum 1) Removing Snap Ring Remove the snap ring on the clutch drum end using a snap ring pliers (5500-96110). Snap Ring Pliers Housing Assy Snap Ring Clutch Drum 16 6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 2) Removing Clutch Drum Hold the drum remover (5500-96120) on the clutch drum, and gently hammer to pull out the clutch drum. Hammer Drum Remover Clutch Drum 6-19 Assembling Cluch Drum 1) Assembling Snap Ring Assembling shall be done by an reverse order to the disassembling. ・ Assemble the clutch drum into the clutch housing and set the snap ring using a snap ring guide (5500-96130) and the snap ring push guide (550096140). Tap the stopper by hand and engage the snap ring into the drum groove. Snap Ring Push Guide Snap Ring Guide Caution: Make sure to replace the snap ring if it is deformed. Snap Ring Clutch Drum 2) Applying grease ・After the assembly, apply molybdenum grease on the clutch drum spline. Molybdenum Grease 17 7. CARBURETOR STRATO STRATO CHARGED CHARGEDENGINE ENGINEGZ25N 7-1 Construction The Strato-charged Engine is applied with a custom designed carburetor employing diaphragm rotary valves and 2 venturies, one for the lead air and the other for the air-fuel mixture. Lead Air To Reed Valve A Lead Air Intake Tube Air Cleaner B Insulator Air-fuel Mixture Throttle Valve A : Lead Air Port Carburetor B : Air-fuel mixture Port 7-2 Function and Operation of Throttle Valve Intake timing for the air-fuel mixture and the lead air are as illustrated below: unit: mm 18.1 Idling Lead air : Close Venturi bore Mixture : Start to open 8 Lead Air block 8 9 Air-fuel Mixture block 9 Mid speed Lead air : Start to open 13.0 Rotary Valve Mixture : Half open The throttle valve has 2 ports. Upper port is for the lead air and lower port for the air-fuel mixture. As shown above, the rotary valves are coaxially arranged while their air passage bores and valve outside diameters differ each other. As the venturi bore sizes also differ each other, air intake timing can be changed by rotation of the rotary valves. 18 High speed Lead air : Full open Mixture : Full open 7. CARBURETOR STRATO CHARGED ENGINEGZ25N 7-3 Specifications Item Unit Specifications Product Name Engine Type GZ25N Carburetor Type Name WYA-1B Part Number 4810-81001 Carburetor Specification Main Jet #38.5 Metering Lever Height mm (in.) 1.5 ±0.16 (0.059 ±0.006) Venturi Bore mm (in.) MIX 9.0 (0.354) AIR 8.0 (0.315) Choke Bore mm (in.) ø13.2 (ø0.5210) 2 Valve Opening Pressure kg/cm (psi) Valve Closing Pressure kg/cm (psi) 2 1.0 2.0 (14.2 28.4) 0.4 1.4 (5.69 19.91) Speed Idling rpm 2800 3200 Clutch engaging rpm 3800 4200 Stall rpm 5650 6150 Operating Speed rpm No Load Max Speed rpm 6000 10000 10000 19 7. CARBURETOR STRATO CHARGED ENGINEGZ25N 7-4 Composition and Inspection a) Adjusting Idle Speed Adjust Screw Adjust Nut Swivel The idle speed is set for 3000rpm at the factory. If it is necessary to adjust the idle speed, use the adjustment screw on the top side of carburetor Screw Bracket Adjustment Screw Washer Adjustment Screw Clip Throttle Valve Carburetor Body O-ring O-ring Gasket Main Jet(♯38.5) Pump Diaphragm (Main Jet No. : #38.5) Spring Lever Gasket Screen Body b) Judgement of the main check valve Valve Pin As illustrated, hold a plastic pipe on the check valve and blow and suck air by your mouth. If the air is stopped by blowing, and open by sucking, the valve has no failure. Screw Diaphragm In case of failure, soak the valve into gasoline for about 10 minutes and repeat blowing and sucking several times. If this is not successful, exchange with new one. (Make sure to check the valve in case fuel is not supplied though the priming pump is operated) Purge body Priming Pump Pump Cove Screw Plastic Pipe Main Check Valve 20 8. TROUBLE SHOOTING STRATO CHARGED ENGINEGZ25N 8-1 Engine does not start Description Cause Countermeasure No spark in the spark plug Spark Plug Magneto Switch 1.Wet spark plug electrodes Make them dry 2.Carbon deposited on the electrodes Cleaning 3.Insulation failure by insulator damage Exchange 4.Inproper spark gap Adjust to 0.6-0.7mm (0.023-0.028in.) 5.Burn out of electrodes Exchange 1.Ignition coil inside failure Exchange 2.Damaged cable sheath or disconnected cable Exchange or repair 1.Switch is OFF ON the switch 2. Switch failure Exchange 3. Primary wiring earthed Repair Sparks appear in the spark plug Compression & fueling is normal 1.Over sucking of fuel Drain excess fuel 2.Too rich fuel Adjust carburetor 3.Overflow Carburetor adjust or exchange 4. Clogging of air cleaner Wash with mixed gasoline 5.Faulty fuel Change with proper fuel Fueling normal but poor compression 1.Worn out cylinder, piston, or piston ring Exchange 2.Gas leakage from cylinder and crank case gasket Apply liquid gasket and reassemble. No fuel supply 1. Choked breather air hole Cleaning 2.Clogged carburetor Cleaning 3.Clogged fuel filter Exchange fuel filter 8-2 Stalled during Operation Description Suddenly stopped Cause Countermeasure 1.Switch is OFF ON the switch 2.Plug cap disconnected Properly fit as original 3.Short circuit of spark plug electrodes by carbon Remove carbon Gradual speed reduction and stalled 4. Switch cable or high tension cable sheath worn out Exchange 5. Ignition coil inside failure Exchange 6. Engine seizure Overhaul 1.Lack of fuel Supply fuel 2.Clogging inside carburetor Cleaning 3.Water mixed to fuel Drain and apply new fuel 21 8. TROUBLE SHOOTING STRATO CHARGED ENGINEGZ25N 8-3 Engine cannot be stopped Description Overheating Cause Countermeasure 1.Lean fuel Adjust carburetor 2.Cylinder fin clogged with dusts Cleaning 3.Inproper fuel Change with proper fuel 4.Carbon deposited inside of combustion Cleaning chamber Switch 5.Spark plug electrode red hot Clean thoroughly and adjust spark gap [ 0.6-0.7mm (0.023-0.028in.) ] 1.Faulty switch Exchange 2.Cable failure Repair 8-4 Lack of output power or unstable revolution Description Cause Compression is normal 1. Air penetration from fuel pipe joints, etc and no misfire 2. Air penetration from intake tube joint or carburetor joint Overheating Others Countermeasure Secure connection Change gasket or tightening screws 3 Water in fuel Change with good fuel 4. Piston start to seizure Filing of seized surface with fine files 5. Muffler choked with carbon Cleaning 6. Crack on lead air intake pipe Exchange 7. Reed valve clogged with dusts or valve tip opening is larger than specification [ 0.2mm (0.008in.) ] Cleaning or exchange components 8. Reed valve stuck Cleaning or exchange 1. Fuel too lean Adjust carburetor 2. Clogging of cylinder fin with dust Cleaning 3. Poor fuel quality Exchange with proper fuel 4. Carbon deposited in the combustion chamber Cleaning 5. Spark plug electrode red hot Thoroughly clean, adjust spark gap [ 0.6-0.7mm (0.023-0.028in.) ] 1. Dirty air cleaner Wash with mixed gasoline 2. Over loading Reduce load Note : Hatched columns above are potential failures unique to the stratified scavenging engine. 22 STRATO CHARGED ENGINEGZ25N 23 R KOMATSU ZENOAH AMERICA INC. 4344 Shackleford Road, Suite 500 Norcross, Georgia, 30093
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