| Technical Index |
| Engine |
| Primary Transmission And Rear Chain |
| Gearbox |
| Carburetor And Air Filter |
| Frame |
| Forks / Shocks |
| Brakes Wheels And Tires |
| Electrical |
| Torque Settings |
| Capacities |
| B50 | B25 | ||||
| Capacity | 499cc (30.5 cu.in.) | 247cc (15 cu.in.) | |||
| Bore | 84mm | 67mm | |||
| Stroke | 90mm | 70mm | |||
| Oil pressure valve | 45-50 lbs p.s.i. | 80-100 lbs p.s.i. | |||
| Compression Ratio | 10:1 | 10:1 | |||
| Spark Plug | Champion N4 or Equivalent. MX N3 | Champion N3 | |||
| Spark Plug Gap | 0,5 – 0,65mm (0.020 – .025 in.) | ||||
| Contact Breaker Gap | 0,38mm (0.015 in.) (Click here for Boyer Ignition) | ||||
| Ignition Timing | 34 degrees BTDC (Fully Advanced) | 37 degrees BTDC (Fully Advanced) | |||
| Piston distance before TDC | 8.7mm (0.342 in.) | ||||
| Valve Clearances Inlet (Cold) | 0,20mm (0,008 in) | ||||
| Valve Clearances Exhaust (Cold) | 0,25mm (.010 in.) | ||||
| Valve spring load open | 214 lbs | ||||
| Valve spring load closed | 81 lbs | ||||
| Inner Valve spring length ( fitted ) | 1.218 in. | ||||
| Outer Valve spring length (fitted) | 1.312 in. | ||||
| Crankcase drive side inner bearing | Hoffmann R.325L Sparepart no: | ||||
| Crankcase drive side outer bearing | Hoffmann LS9 (Ball) FAG 1640 Sparepart no: 65-5883 ( 37-2363 ) 7/8"x2"x9/16" | ||||
| Crankcase gear side bearing | Hoffmann R.325L ( SKF NJ305.ECP ?? ) Sparepart no: 24-0724 ( 70-9974 ) 25 X 62 X 17MM | ||||
| Big-end diameter (rod) | 1.8116-1.8110 | ||||
| Crankpin diameter | 1.4961-1.4957 | ||||
| Gearbox Mainshaft left side | Hoffmann 130 ( SKF 6206 RS1 with one side rubber seal) Sparepart no: 29-3837 ( 70-8014 ) 30 X 62 X 16 mm | ||||
| Gearbox Mainshaft left side Oil Seal | 1.562" x 2.062" x 0.187" | ||||
| Gearbox Mainshaft right side | Hoffmann LS7 ( SKF RLS5 ) Sparepart no: 90-0011 15,875 X 39,668 X 11,113 mm | ||||
| Gearbox Layshaft | Torrington B108 2 pcs ( SKF BMNJL108 ) Sparepart no: 40-3292 5/8 X 13/16 X 1/2" | ||||
| Motor no on left side of crankcase below cylinder baseFrame no on left side of front motor lug or frame head | |||||
| Engine Sprocket | B50 28 Teeth ( B25 23 Teeth ) |
| Clutch Sprocket | 52 Teeth |
| Primary Chain | Dubble Row, 3/8 Pitch duplex 70 Pitches |
| Rear Chain | 105 Pitches,5/8 x 1/4 in. (107 Pitches B50T) (106 Pitches B50MX) |
| Rear Chain line rear | 2 7/8 in. |
| Clutch Pushrod Length | 22.9mm (9.0 in.) |
| Clutch Pushrod Diameter | 0.1875 in. |
| Clutch Plates | 5 fiber clutch, 5 metal clutch |
| Thickness of friction plate | 4.2mm (0.167 in.) |
| Free length of springs | 42mm (1.66 in.) |
| Clutch rollers | 25 pcs rollers 3/16 X 3/16" |
|
Four speed, Multiplate clutch with built- in shock absorber |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gearbox ratios | Gear Ratio | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| First | 2:65 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Second | 1:64 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Third | 1:24 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Top | 1:0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Biggest Gear box sprocket is 19 teeth, Smallest rear sprocket is 47 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Ratios Overall
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Standard B50 SS & T Amal R930/62 |
|||||
| Main Jet | 106 | ||||
| Needle Jet | 200 | ||||
| Needle Position | Top (1) | ||||
| Throttle Valve | 3 1/2 | ||||
| Throttle spring free length | 64mm (2.5 in.) | ||||
| Air Filter | Pleated impregnated paper | ||||
| B50 MX 1971-1972 R932/18,B50 MX 1973 R932/28) | |||||
|
Main Jet |
106 | ||||
| Needle Jet 1971-1972 | 250 | ||||
| Needle Jet 1973 | 180/250 | ||||
| Needle Position | 2 | ||||
| Throttle Valve 1971 – 1972 | 3 | ||||
| Throttle Valve 1973 | 3 1/2 | ||||
| Air Filter | Pleated impregnated paper | ||||
| Standard B25 ( Amal 932 28mm) | |||||
|
Main Jet |
260 | ||||
| Needle Jet | 106 | ||||
| Needle Position | Top (1) | ||||
| Throttle Valve | 3 1/2 | ||||
| Needle | 928 / 107 | ||||
| Choke Tube | 928 / 107 | ||||
| Air Filter | Pleated impregnated paper | ||||
| Index | |||||
|
Welded frame with large diameter top tube for strength. Top tube doubles Swinging arm with quadrant adjustment for rear chain.
|
|
|
Dimensions |
|
| Height | 1140mm (45 in) |
| Length | T & SS 2160mm (85 in.) MX 2090mm (82.5 in) |
| Wheelbase | 1410mm (55.5 in) |
| Weight (SS) | 140,6 Kg (310,0 lbs) |
| Weight (T) | 135,2 Kg (298,0 lbs) |
| Weight (MX) | 116 Kg (256 lbs) |
| Width | T & SS 737mm (29,0 in) MX 850mm (33.5 in.) |
| Ground clearance (SS) | 178mm (7,0 in) |
| Ground clearance (T & MX) | 190mm (7,5 in) |
| Seat Height |
813mm (32,0 in) |
| Fork angle | 63 degrees |
| Lock angle | 45 degrees |
| Dry weight engine | 38,5kg (85lbs.) |
| Swing arm bearing | 2 pcs Torrington B.1616 ( SKF B1616 ) Art no: 83-2245 1 X 1-1/4 X 1" |
|
Forks ( Telescopic with internal Springs Hydraulically damped) |
|
| Fork spring | 97-4011 |
| Sping rating | 25 lbs. / in. |
| Total Fork Travel | 17,1mm (6 3/4 in.) |
| Trail | 100mm (3.96 in.) |
| Fork Leg Oil Capacity | 190 cc (2/5 U.S. pints 1/3 UK pint ) in each leg |
| Spring Free Length | Main 482mm ( 19.2 in.) Recoil 23.8mm (0.94in.) |
| Fork Bearings | Timken LM11949L Art no: 97-4031 1,781 X 0,75 X 0,61" |
|
Shocks |
|
| Damper unit ( Girling no) | 64052453 (MX 64052487) |
| Adjustment | Cam |
| Spring rating | 100 (MX 70-100) |
| Movement | 65mm (2.56 in.) (MX 74,5mm 2.94in.) |
| Extended Length | 12.9 in. |
Drumbrake
with individual snail cam shoe adjustment
Front
Wheel T
Front
Wheel MX
Rear
wheel
Drumbrake
with floating cams
|
Front |
|
| Rim Size | WM2 X 18 |
| Tire Size | K 70 3.25 x 18 in. |
| Tire Pressure | 22 p.s.i. |
|
Front |
|
| Drum Type | Twin Leading Shoe |
| Drum Diameter | 203mm (8 in.) |
| Lining area | 75 cm2 (11.62 sq.in.) |
| Rim Size | WM1 X 20 |
| Tire Size | 3.00 x 20 in. |
| Tire Pressure | Off road 10 p.s.i. On road 22 p.s.i. |
|
Front |
|
| Drum Type | Single leading shoe |
| Drum Diameter | 152mm (6 in.) |
| Lining width | 22,2mm (7/8 in.) |
| Lining length | 147mm (5.78 in.) |
| Lining thickness | 4mm (5/32 in.) |
| Lining area | 32,6 cm2 (5.06 sq.in.) |
| Rim Size | WM1 X 20 |
| Tire Size | 3.00 x 20 in. |
| Tire Pressure | 8 p.s.i. |
|
Front |
|
| Drum Type | Single leading shoe |
| Drum Diameter | 152mm (6 in.) |
| Lining width | 22,2mm (7/8 in.) |
| Lining length | 147mm (5.78 in.) |
| Lining thickness | 4mm (5/32 in.) |
| Lining area | 32,6 cm2 (5.06 sq.in.) |
| Rim Size | SS WM2 X 18 ( T & MX WM3 X 18 ) |
| Tire Size | SS 3.50 X 18in. T & MX 4.00 X 18 |
| Tire Pressure | SS 24 p.s.i., T Off road 14 p.s.i On road 24 p.s.i., MX 12 p.s.i.. |
|
Rear |
|
| Drum Diameter | 178mm (7 in.) |
| Lining width | 28,6mm (1 1/8 in.) |
| Lining length | 175mm (6.88 in.) |
| Lining thickness | 4,8mm (3/16 in.) |
| Lining area | 49,9mm (7.74 in.) |
| Bearings | Hoffman 120 ( SKF6204 2RS ) Art no: 37-1340 ( 37-0653 ) 20 X 47 X 14 mm |
|
General |
|
| Voltage | 12 V Positive earth/ ground |
| Alternator | RM 21 115 watt (MX RM.22) |
| Rotor | 54213901 |
| Rectifier | 2DS 506 |
| Zener Diode | ZD715 (MX -) |
| Battery | PUZ5A |
| Capacitor | 2MC |
| Coil | 17 M 12 (MX Wipac ET) |
| Contact Breaker | 6CA |
| Igition capacitor | 54441582 |
| Fuse | 35 Amp |
| Flasher Unit | 8FL |
| Master ignition switch | 149.SA |
|
Bulbs |
|
| Headlight | 12 V 45/40 Watt |
| Tail / Stop light | 12V 21/ 6 Watt |
| Parking | 12V 6 Watt Bayonet |
| Direction Indicators | 12V 21 Watt |
| Warning Lights | 12V 2 Watt |
| Cylinder head nuts B25 3/8 U.N.F. | 26-28 ft./lb. 3.6-3.9 kg/m |
| Cylinder head nuts B25 B.S.C. | 18-20 ft./lb. 2.5-2.8 kg/m |
| Cylinder head nuts B50 5/16 U.N.F. | 18-20 ft./lb. 2.5-2.8 kg/m |
| Cylinder head nuts B50 7/16 U.N.F. | 30-33 ft. /lb. 4.1-4.6 kg/m |
| Flywheel bolts (B25) 3/8 U.N.F. | 50 ft./lb. 6.9 kg/m |
| Con rod nuts (B25) 5/16 U.N.F. | 22 ft./lb. 3.0 kg/m |
| Rocker box nuts 5/16 U.N.F. | 8 ft./lb. 1.1 kg/m |
| Crankpin nuts B50 7/8 W.F. | 200 ft./lb. 27.6 kg/m |
| Crankshaft pinion nut B25 5/8 B.S.C. | 50-55 ft./lb. 6.9-7.6 kg/m |
| Crankshaft pinion nut B50 5/8 U.N.F. | 55 ft./lb. 7.6 kg/m |
| Kickstart ratchet nut 1/2 B.S.C. | 38-40 ft./lb. 5.3-5.5 kg/m |
| Oil Pump stud nuts 1/4 U.N.F. | 5-7 ft./lb. 0.7-1.0 kg/m |
| Oil Pump stud nuts 1/4 U.N.F. | 5-7 ft./lb. 0.7-1.0 kg/m |
| Rotor mounting nut B25 5/8 B.S.C. | 60 ft./lb. 8.3 kg/m |
| Rotor mounting nut B50 5/8 U.N.F. | 60 ft./lb. 8.3 kg/m |
| Stator mounting nuts 1/4 U.N.F. | 5-7 ft./lb. 0.7-1.0 kg/m |
| Clutch center nut 1/2 B.S.C. | 55-60 ft./lb. 7.6-8.3 kg/m |
| Gearbox sprocket nut 1 3/16 W.F. | 100 ft./lb. 13.8 kg/m |
| Fork leg top nuts 1 3/16 U.N.S | 50 – 55 ft. /lb. 6.9-7.6 kg/m |
| Fork yoke pinch bolts 3/ U.N.F. | 23 – 25 ft. /lb. 3.2-3.5 kg/m |
| Fork stanchion end plug 1 3/16 U.N.F. | 25 ft./lb. 3.5 kg/m |
| Timing and primary cover screws 1/4 U.N.C. | 3.5-4.5 ft./lb. 0.5-0.6 kg/m |
| Auto-adance unit bolt 1/4 U.N.F. | 6 ft./lb. 0.8 kg/m |
| Carburetter flange nuts 5/16 B.S.C. | 10 ft./lb. 1.4 kg/m |
| Flasher stanchion to flasher body nut 7/8 U.N.C. | 3 ft./lb. 0.4 kg/m |
| Zenor Diode nut | 24 -28 ft./lb. kg/m |
| Coil bracket nuts | 1 ft./lb. kg/m |
| Oil pressure release valve 7/8 U.N.C. | 25 ft./lb. 3.5 kg/m |
| Drawings over cover screews here | |
| Engine oil tank | 2,25 Liters (4 3/4 U.S. Pints 4 UK Pints) |
| Primary Chaincase |
140 cc, (1/4 Pint UK, 1/3 Pint USA) |
| Gearbox | 280 cc (1/2 Pint UK, 5/8 Pint USA) |
| Front Forks |
190 cc, (1/3 Pint UK, 2/5 Pint USA) |
| SS fuel tank | 13,5 Liters (3 1/2 U.S. Gallons 3 UK Gallons) |
| T fuel tank | 9 Liters (2 1/2 U.S. Gallons 2 UK Gallons) |
| MX fuel tank (Narrow) | 4,5 Liters (1 1/4 U.S. Gallons 1UK Gallons) |
Frame
Swing
AMAL
AMAL MK1 Parts
Gearbox
Wheels
Gearbox
Electrics