FOREWORD This Shop Manual is a servicing guide for the Z50A. Many photographs and illustrations were used to provide the serviceman with clear and easy understanding. To ensure proper servicing, the special tools must be used and all repairs made to the specified tolerances. HONDA MOTOR CO., LTD. CONTENTS MAIN FEATURES OF Z50A............................................ 1 SPECIFICATION TABLE................................................ 3 SPECIAL TOOL SET .................................................. 4 ENGINE .............................................................. 6 1. Engine Assembly Diagram ...................................... 6 2. Engine Removal ................................................ 7 3. Engine Installation .............................................. 7 4. Lubrication (Oil Pump).......................................... 8 5. Cylinder and Cylinder Head...................................... 9 6. Piston and Piston Ring.......................................... 15 7. Clutch........................................................ 17 8. Crankshaft ...........,........................................ 18 9. Transmission .................................................. 20 10. Gear Shift Mechanism .......................................... 21 11. Kick Starter.................................................... 23 12. Carburetor...................................................... 24 TROUBLE SHOOTING TABLE .......................................... 27 FRAME 1. Front Suspension .............................................. 31 2. Rear Brake.................................................... 31 WIRING DIAGRAM.................................................... 32 MAIN FEATURES OF Z50A • The overhead cam design enables a quiet operation and a constant high output over a broad speed range starting at slow speed with very little effort. • Incorporation of the oil damper type cam chain tensioner automatically maintains the proper tension and minimizes the chain noise, further, chain adjustment is unnecessary. • Riding is simplified by the use of the automatic clutch which is interconnected with the gear change pedal. • Metal screen and centrifugal filter assures only clean oil to lubricate the critical moving parts. • Foldable handle bar makes storing in narrow space possible. • Frame is welded pipe backbone design having a double channel welded to a single main pipe to reduce weight. • To prevent spillage of fuel during transportation fuel shut off valves are provided in the filler cap and the carburetor. GENERAL EXPORT TYPE TYPE (From F. No. 120001) U.S.A. TYPE (From F. No. 270236) 3 SPECIFICATION TABLE GENERAL EXPORT I U.S.A. TYPE I U.S.A. TYPE I TYPE '(From No. F. 120001 )'(From No. F. 270236) DIMENSION Overall length 1,270mm (50.0 in) |1,280 mm (50.4 in) Overall width 635 mm (25.0 in)| 590 mm (23.2 in) Overall height 1,000 mm (39.4 in) 860 mm (33.9 in) Wheel base 880 mm (34.7 in) Min. ground clearance 1 70 mm ( 6.7 in) Curb weight 49 kg (108 lbs) | 50 kg (110 lbs) | 53.5 kg (1 1 8 lbs) FRAME Suspension (F) Telescopic fork | Suspension (R) Rigid frame I Brakes Internal expansion I Fuel tank capacity 2.5 lit. (0.7 U.S. gal., 0.6 Imp. gal.) Trail 40 mm (1.57 in) Caster 67° Tire size and air pressure (F & R) 3.50-8, 1.0 kg/cm2 (14.2 psi) ENGINE Cylinder layout Single, tilt up 10° from horizontal Valve arrangement OHV, overhead camshaft Bore and stroke 39X41.4 mm (1.535X1.630 in) 1 Compression ratio 8.8 1 Displacement 49 cc (3.0cu-in) 1 Oil capacity 0.8 lit. (1.7 U.S. pt.( 1.4 Imp. pt.) 1 Lubrication Pressure lubrication & wet sump Oil filters Centrifugal and screen mesh Reduction ratios 1 Primary 3.722 1 Secondary 2.615 | 2,917 Gear ratios 1st 3.182 2nd 1.824 3rd 1.190 I Starting method Kick starter PERFORMANCE I Max. torque 0.31 kg-m/4,200 rpm (2.2 ft-lb/4,200 rpm) Max. output 1.95 ps/5,000 rpm I Min. turning circle 2.6 m (8.6 ft) ELECTRICAL Ignition Flywheel magneto I Spark plug NGK C-6H or ND U20FS I Head light 6V-15W | 6V-15/15W | Tail/stop light 6V-8/3W | 6V-17/5.3W 4 SPECIAL TOOL SET Ref. No. Tool No. Description 07000-04511 Z50M/Z50A Special tool set 1 07001-03602 Inlet valve seat cutter, 90° 2 07002-03602 Exhaust valve seat cutter, 90° 3 07003-03601 Inlet valve seat top cutter 4 07004-03601 Exhaust valve seat top cutter 5 07005-03601 Inlet valve seat interior cutter 6 07006-03601 Exhaust valve seat interior cutter 7 07007-03601 Valve seat cutter holder 8 07016-00102 Flywheel puller 9 07025-00102 Flywheel holder 10 07081-00101 Tappet adjusting socket wrench 11 07008-24001 Valve guide reamer 12 07086-00102 Lock nut wrench, 14 mm 13 07087-00101 Tappet lock nut socket wrench 14 07038-01101 Clutch disassembling & assembling tool 5 Ref. No. Tool No. Description 15 07022-04001 Drive sprocket holder 16 07047-04001 Valve guide remover 17 07046-21601 Valve guide driver 18 07024-03501 Clutch outer holder 19 07031-20001 Valve lifter 20 07784-99908 Universal bearing puller 21 07048-81501 Bearing driver 22 07072-00101 Pin spanner, 36 mm 23 07048-04501 Front wheel oil seal driver 24 07054-04501 Rear wheel bearing driver 25 07048-04505 Bearing & oil seal driver handle 26 07083-03001 Stem nut socket wrench 27 07071-25001 Main switch pin spanner 28 07997-05101 Valve seat cutter case 29 07790-29201 Tool case (A) ENGINE 1. ENGINE ASSEMBLY DIAGRAM Fig. 1 7 2. ENGINE REMOVAL 1. Loosen the muffler flange and mounting bolts, and remove the muffler 2. Disconnect the throttle cable from the carburetor. 3. Detach the high tension cord by pulling the plug cap off the spark plug. 4. Disconnect the electrical wiring (Fig. 2), 0 Electric leads coupler Fig. 2 5. Set the fuel cock to the OFF position and disconnect the fuel tube from the carburetor. 6. Unscrew the left crankcase cover mounting screws and remove the cover. 7. Unfasten the drive chain joint clip and disconnect the chain. 8. Remove the two engine hanger bolts and dismount the engine from the frame (Fig. 3) ® Engine hanger bolts Fig. 3 3. ENGINE INSTALLATION Perform the engine installation in the reverse order of the engine removal described above. Note: When installing the drive chain joint clip, make sure that the open end of the clip is in the opposite direction to the normal chain rotation (Fig. 4.) Fig. 4 Chain joint clip installation Fig. 5 Engine oil routes 4. LUBRICATION (OIL PUMP) A. Description The engine oil which has been picked up by the trochoid pump is diverted into two routes (Fig. 5). Route one : Oil is sent through the right crankcase —* right crankcase cover —> centrifugal filter—-? connecting rod large end rollers. Route two : Oil is sent through the cylinder stud bolt —» rocker arm side cover—? camshaft profiles and bearings —? valve mechanism ® Oil pump assembly Fig. 6 B. Disassembly 1. Unscrew the right crankcase cover mounting screws and remove the cover. 2. Remove the clutch outer cover. 3. Unscrew and remove the 14 mm clutch lock nut and washer, and then remove the clutch assembly. 4. Loosen the three 6 mm oil pump mounting bolts and remove the oil pump assembly. 5. Loosen the three cross screws attaching the oil pump cover, the oil pump can then be disassembled (Fig. 6). 9 C. Inspection 1. Turn the oil pump drive shaft by hand and make sure that it is turning smoothly. Measuring the clearance between the outer rotor and the pump body. Insert the thickness gauge between the outer rotor and the pump body (Fig. 7). inch (mm) Standard Value Serviceable Limit 0.004-0.006 (0.10-0.15 mm) Replace if over 0.0079 (0.20 mm) ® Thickness gauge Fig. 7 Pump body ® Outer rotor 3. Measuring the end clearance of the rotor. Place a straight edge across the pump housing and check the clearance of the rotor with a thickness gauge (Fig. 8). Standard Value Serviceable Limit 0.0008-0.0027 (0.02-0.07 mm) Replace if over 0.0047 (0.12 mm) D. Reassembly Perform the reassembly in the reverse order of disassembly procedure. Particular attention should be paid to the following items (Fig. 9). 1. Make sure that the parts are thoroughly cleaned before assembly. 2. After completing the reassemb'y of the pump, check to make sure that the pump is operating smoothly by turning the shaft by hand before mounting the pump in the crankcase. 5. CYLINDER AND CYLINDER HEAD A. Description The cylinder head is made of aluminum alloy to improve the cooling effect. Cylinder is made of special cast iron which provides good wear characteristics without being affected by high temperature and pressure. 0 Oil pump body gasket © Oil pump dwell pin (D Oil pump body ® 6mm hex. boltOil pump drive shaft ® Oil pump cover gasket £.0004-0.0012 (0.01-0.03 mm) 0.0012-0.002 (0.03-0.05 mm) Serviceable Limit Replace if over 0.0032(0.08 mm) Replace if over 0.004 (0.10 mm) 4. Measuring the valve dimension The valve stem diameter is measured with a micrometer. (Fig. 20) Item Standard Value Serviceable Limit Inlet 0.2148-0.2187 (5.455-5.465mm) Replace if under 0.2126 (5.40mm) Exhaust 0.2070-0.2109 (5.435-5.445mm) Replace if under 0.2048 (5.38mm) Replacing the valve guide If the valve guide is worn excessively and requires replacement, follows the procedure below. a. Remove the valve guide from the cylinder head using the valve guide remover (Tool No. 07047-04001). b. Install the new valve guide using the valve guide driver (Tool No. 07046-21601), and carefully drive the guide into the head. The replacement valve guide should be one that is of an oversize. c. After the new valve guide has been installed, it must be reamed to the proper finish size using a guide reamer (Tool No. 07008-24001). Excercise care when using the reamer and apply small amount of oil occasionally to lubricate when the reamer starts to operated hard, pull out the reamer and remove the metal chip before continuing to ream. The standard valve guide diameter is 0.2156-0.2159 (5.475-5.485 mm). Measurement can be made with a cylinder gauge (Fig. 22). ® Small dial gauge (2) Valve Fig. 19 (D Micrometer Fig. 20 (2) Valve © Valve guide remover Fig. 21 (T) Valve guide reamer Fig. 22 14 (D Vernier caliper (2) Valve spring Fig. 23 (T) Micrometer Fig. 24 Camshaft (D Cylinder gauge Fig. 25 ^IPe © "0" mark spark plug; -b 'SPEEDOMETER LAMP "6V-1.5W Bk 6 Bk 3^ HEADLIGHT , LG-. 6V-15W T! Bk R Bl Gr ILL' PiMlGNITION SWITCH S ¦^ W-TUBE -.....n ?P~^— TAIL AND STOPLIGHT ^ 6V-8/3W ^STOP SWITCH G : Green Br : Brown Y : Yellow LG : Light green Bk: Black Gr : Grey Bl : Blue R : Red W : White U.S.A. TYPE (From F. No. 120001) High beam indicator light u2)(6V-1.5W) ;/wni o-G/1 V _ W-Tube I Bu » IG i E (HO OhO _£fco. o+o Bl.. Bu.. Br.., G.... R.... W... Y.... .. Black ..Blue . Brown Green . Red . White ...Yellow G/W............Green/White Br/W.........Brown/White Bu/W.........Blue/White G/Y............Green/Yellow Br/R......... Brown/Red G/Y............Green/Yellow U.S.A. TYPE (From F. No. 270236) STOP SWITCH(FRONT) STOP SWITCH(REAR) STOp SW|TCH(REAR) Uifi HIGH BEAM INDICATOR LIGHT 6V15W TAIL/STOPLIGHT 6V17/5 3W G/Y-c=m3/Y^ HEADLIGHT 6V15/15W Br/*B£ Br/W WBu BEAM SELECTOR SWITCH FLYWHEEL AC. GENERATOR MAIN SWITCH ARRANGEMENT IG E c, C2 SL HO c3 HL Key removal OFF O o ol O Key can be removed I O o O Key can not be removed n O c^ o O ¦o El................Black G/W- Bu................Blue Br/W- Br................Brown 6/Y- Gr................Grey Bl/W- R ................Red Bu/W- W................White Green with White spiral Brown with White spiral Green with Yellow spiral ¦Black with White spiral Blue with White spiral