location and numbers BSA WD M20
Bearing numbers listed shown are the numbers used by one of the original suppliers. BSA used a number of different companies to supply bearings and the numbers listed can easily be cross referenced by a bearing factor to the modern equivalent where available.
Clutch loose: 1/4x1/4 rollers Qty 22
Steering head cups and cones loose: 1/4dia. Ball bearings Qty 40
Front wheel bearing: 2K1178X and 2K1130N1 (inners and outers numbered separately)
Rear wheel bearing: 2K05079 and 2Ko5185 (inners and outers numbered separately)
The rear wheel bearings can be replaced with a modern equivalent, Bearing: no.30204
Timing side lipped roller: MRJA7/8
Timing side ball: RHP MJ 7/8" - SKF RMS7 - FAG MS-9
Drive side lipped roller: MRJA25
Drive side ball: 6205C3
Engine main bearings should be a C3 class fit. Specify this when ordering.
Gearbox main bearing: 6207
Gearbox mainshaft bearing (Kickstart end): LJ3/4
Dynamo bearing (drive end): 6202
Dynamo bearing (Brush end, 60 watt only): 608
Wartime 45watt ‘short body’ dynamos were fitted with an ‘Oilite’ bush on the brush end. of the armature. The 60watt ‘long body’ dynamo was introduced in 1954 and replaced the earlier type. This later type is frequently found on earlier machines.
Points end bearing: E15
Drive end bearing. Two types of drive end bearing were used in Lucas ‘Magdyno’ mags. The periods of use overlapped each other so it is not possible to be specific about which type would be used in a given year as this period of change coincided with the late pre war and wartime period. 
Type 1: N3048
Type 2: E15
The E15 is the more common and later type. N3048 is generally no longer available.
Ian Wright