| 1192cc (1200) | 77mm x 64mm |
| 1285cc (1300, 1300A and 1303) | 77mm x 69mm |
| 1493cc (1500) | 83mm x 69mm |
| 1584cc (1600, 1302S and 1303S) | 85.5mm x 69mm |
| 1192cc | 7.0:1 |
| 1285cc | 7.3:1 (1303 - 7.5:1) |
| 1493cc | 7.5:1 |
| 1584cc | 7.5:1 |
| Nos. 1, 2 and 3 | 2.1654 |
| No. 4 | 1.5748 |
| Nos. 1, 3 and 4 | Sleeve type, aluminium alloy |
| No. 2 | Split shells, aluminium alloy |
| Nos. 1, 2 and 4 | 0.0016 to 0.004 (limit 0.0072) |
| No. 4 | 0.002 to 0.004 (limit 0.0075) |
| Regrind undersizes | -.25mm, -.50mm and -.75mm |
| End float | 0.0027 to 0.005 (limit 0.006) |
| Crankpin diameter | 2.1654 |
| Crankpin regrind undersizes | -.25mm, -.50mm and -.75mm |
| Running clearance, big-end | 0.0008 to 0.003 (limit 0.006) |
| End float, big-end | 0.004 to 0.016 (limit 0.028) |
| Maximum permissible weight variation | 0.18 oz |
| Type | Aluminium alloy with steel strut |
| Running clearance (½ inch below crown at right angles to gudgeon pin) | 0.0015 to 0.002 (0.0024 on 1500) (limit 0.008) |
| Weight tolerance, maximum | 0.18 oz |
| Piston rings | 2 compression, 1 oil scraper |
| Side clearance, top compression | 0.0027 to 0.0035 (limit 0.005) |
| Side clearance, second compression | 0.002 to 0.0027 (limit 0.004) |
| Side clearance, oil control | 0.0012 to 0.002 (limit 0.004) |
| Compression ring gap | 0.012 to 0.018 (limit 0.035) |
| Oil control ring gap | 0.010 to 0.016 (limit 0.037) |
| Gudgeon pin type | Fully floating, located by circlips |
| Gudgeon pin bush | Bronze, pressed into connecting rod |
| Gudgeon pin clearance in bush | 0.0004 to 0.0008 (limit 0.0016) |
| Type | Cast iron, three bearings |
| Bearings | Split, steel-backed, white metal lined |
| Running clearance | 0.0008 to 0.002 (limit 0.0047) |
| End float | 0.0024 to 0.0045 (limit 0.0056) |
| Backlash between timing gears | 0.0000 to 0.002 |
| Diameter | 0.7466 to 0.7472 (limit 0.7452) |
| Working clearance | 0.0008 to 0.0024 (limit 0.0047) |
| Rocker shaft Diameter | 0.7073 to 0.7080 (limit 0.7069) |
| Running clearance or rocker | 0.0006 to 0.002 (limit 0.0031) |
| Head diameter, inlet: | |
| 1192cc | 1.24 |
| 1285cc | 1.3 |
| 1493cc and 1584cc | 1.4 |
| Head diameter, exhaust: | |
| 1192cc and 1285cc | 1.18 |
| 1493cc and 1584cc | 1.26 |
| Seat angle | 45° |
| Stem diameter, inlet | 0.3126 to 0.3130 |
| Stem diameter, exhaust | 0.3114 to 0.3118 |
| Stem to guide clearance, inlet: | |
| 1192cc and 1285cc | 0.0020 to 0.0030 |
| 1493cc and 1584cc | 0.008 to 0.009 |
| Stem to guide clearance, exhaust: | |
| 1192cc and 1285cc | 0.0031 to 0.0041 |
| 1493cc and 1584cc | 0.011 to 0.012 |
| Free length: | |
| Free length: 1192cc and 1285cc | 1.89 |
| Loaded length: | |
| 1192cc | 1.32 at ±7 lb |
| 1285cc, 1493cc and 1584cc | 1.22 at 126 ±8 lb |
| Inlet opens and closes: | |
| 1192cc | 6° BTDC, 35½° ABDC |
| 1285cc, 1493cc and 1584cc | 7½° BTDC, 37° ABDC |
| Exhaust opens and closes: | |
| 1192cc | 42½° BBDC, 3° ATDC |
| 1285cc, 1493cc and 1584cc | 44½° BBDC, 4° ATDC |
| Inlet and exhaust (cold) | 0.004 (0.2mm) |
| End float in housing (with gasket) | 0.003 to 0.007 |
| Backlash between gears | 0.001 to 0.003 |
| Pressure (hot, SAE.20 oil) | 7 lb/sq inch (idling) |
| Pressure (hot, SAE.20 oil) | 28 lb/sq inch (at 2500 rev/min) |
| Relief valve spring free length | 2,480 ±0.040 |
| Load when compressed to 0.930 | 17 lb |
| Clearance between fan and fan housing | 0.065 |