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.
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) .....................................................
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.
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.
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.
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).
3. OUTLINE DRAWING STRATO CHARGED ENGINEGZ25N 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.
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.
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.
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.
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6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-2 Removing of Clunch Shoe 6-3 Mounting of Clutch Shoe : : Caution: Care for orientation of the wave washers and clutch shoe.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-5 Removing Recoil Pulley Note: Pulley screw is right turn screw. 6-6 Assembling of lgnition Coil 6-7 Installing of Spark Plug 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.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-8 Laying of Switch Cable 6-9 Fitting of Plug Cap 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 Caution: Hard hammering may damage the big end of the connecting rod.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-11 Installing of Piston 6-12 Assembling of Piston Pin Circlip Caution: Deformed circlip may come off during engine operation and damage the engine. 6-13 Direction of Setting 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.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-14 Positioning of Lead Air Intake Tube F S S F 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.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 6-17 Mounting of Reed Valve Important: Check the gap between the valve case and the reed valve. Replace with new valve if the gap is larger than 0.2mm (0.008in.), or the valve is distorted.
6. SERVICE GUIDE STRATO CHARGED ENGINEGZ25N 2) Removing Clutch Drum Hammer Drum Remover Clutch Drum 6-19 Assembling Cluch Drum 1) Assembling Snap Ring 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.
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.
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.) Venturi Bore mm (in.) Choke Bore mm (in.) 1.5 ±0.16 (0.059 ±0.006) MIX 9.0 (0.354)AIR 8.0 (0.315) 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.
7. CARBURETOR STRATO CHARGED ENGINEGZ25N 7-4 Composition and Inspection a) Adjusting Idle Speed Screw Bracket Adjustment Screw Washer Adjustment Screw Throttle Valve Carburetor Body O-ring Main Jet(38.
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.
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.
STRATO CHARGED ENGINEGZ25N 23
R KOMATSU ZENOAH AMERICA INC.
