| January | — | — | rotocap valve rotating device for up to 2500RPM |
| January | — | — | lifters- smaller diameter contact flange |
| January | — | 141 201 | square boss heads - 004� valve adjustment sticker added |
| February | — | 141 671 | crankshaft bearing #2 larger oil drilling pocket |
| March | — | — | crankshaft bearing #2 larger oil drilling pocket |
| March | — | — | crankshaft bearing #2 larger oil drilling pocket |
| April | — | 143 507 | thick walled valve spring caps |
| August | — | — | 124A and 126A now 85mm pistons cam bearing shells added, connecting rods have bolts, more cooling fins added, different style pushrods |
| August | — | 146 528 | crank bearing #2, steel backed shells |
| September | — | — | crank bearing #2, steel backed shells |
| October | — | 148 421 | cover plate and governor drive changes, 122 different exhaust valves |
| November | — | — | radii of main bearings #1 and #3 rolled in |
| November | — | — | radii of main bearings #1 and #3 rolled in |
| November | — | 149 400 | 3 upper studs now longer and sunk deeper into case |
| December | — | — | reinforced angle on front cover plate |