BSA Bearings

NOTE: This is an early draft for review purposes only. Take everything with a large grain of salt


This BSA bearing quick reference is inspired by the Norton Owners Club (NSW) Commando bearing guide. While later BSA parts books and manuals provided much more information regarding the bearings fitted than the Norton equivalents, it is still somewhat fiddly to work through the parts books and / or factory workshop manuals to find what bearings are required.

BSA, like most mototcycle manufacturers, fitted a number of different bearing types to the models over the years. Plain bushes and slipper shells tend to be specialist items, but the various ball and roller bearings were off-the-shelf components which should still be available from industrial bearing suppliers.


The aim of this guide is to eventually compile a full list of off-the-shelf bearings and oil seals, both original fitment and modern cross-references) for all post-War BSA models.

Please note that this is (and probably will remain) a work in progress. We try our best, but don't guarantee to get it all correct. Suggestions and corrections will be incorporated as time permits.


Information for this guide has been obtained from BSA manuals, bearing cross-references, Ruper Ratio's Unit Singles book and contributions from other BSA enthusiasts

General bearing stuff

Bearings come in 4 basic forms


bushes are generally machined from sintered bronze, and can be made by any machinist with access to a lathe and supplies of bearing stock. Unless you have ready (cheap) access to a lathe, expertise and sintered bronze rod it is usually best to buy bushes ready-made from a motorcycle parts supplier. Bushes tend to be used in low(er) friction / limited space locations with a reasonable oil supply. Most camshaft and gear pinions run on bushes, as do many gearbox layshafts. Gudgeon pins (wrist pins for the Americans) also usually run on bushes. Bushes are also used for light loads in applications with limited lubrication, such as rocker shafts. Bushes have a high load-carrying capacity

slipper shells are thin steel shells with a lining of softer metal (usually babbit, white metal or aluminium alloy) for the friction surface. The bearing should have no metal-to-metal contact, but relies on an oil film between the disparate metal surfaces. The usual application is for connecting rod big-end shells running on one-piece crankshafts. The infamous BSA twin "timing side bush" is actually a cylindrical slipper shell. Used slipper shells can be re-metalled by specialists, but it is usually best to buy new replacements from a motorcycle parts supplier. Slippers have a high load-carrying capacity and require good high-pressure oil supply

Ball bearings come in 2 forms, loose or caged. Loose balls are generally only used in steering head races or (very early) wheel bearings. The races (cup and cone) are specialist items, but the balls should be avaiilable from bearing suppliers. The ball bearings used most often are ball journal bearings, which come complete with the inner and outer races (cup and cone). The balls are held in place by a cage, which may be made from steel, brass or polyamide. Brass cages tend to be best for engine and gearbox use. Some applications also have a cage without the cup and cone. The BSA 6-spring clutch used a pair o open ball cages.
Ball bearings have a much lower load-carrying capacity than bushes or rollers, but can carry axial loads as well as radial loads. This makes them useful in situations where a shaft has to be held in place with minimal sideways movement. Ball bearings can work in poorly lubricated environments, and sealed pre-lubricated ball bearings are to be preferred ito unsealed versions n exposed applications such as wheel bearings.

Roller bearings can come loose or caged. Rollers also come in various aspect ratios. Long thin rollers are referred to as needle rollers. Rollers can also have various degrees of radius at the ends, ranging from very sharp to rounded.
Roller bearing assemblies are either parallel or taper. Parallel rollers have a very good radial load-carrying capacity but are quite poor for axial loads. Tapered rollers have good radial and axial load-carrying capacity - in *one* direction. They tend to be used in pairs at both ends of a shaft (eg the steering heads of the oil-in-frame twins, car wheel bearings) and need a slight pre-load to stop them chattering. Needle rollers come in parallel or radial configurations. radial needle rollers are used as thrust bearings. They have a very high axial load capacity, but next to no radial capacity.
Roller bearings can work with light lubrication. Sealed pre-lubricated rollers are to be preferred to unsealed rollers in exposed applications

BSA engine and gearbox bearing units generally seem to be C3 clearance (larger clearance than standard). Brass cages are preferred. Brass is comparatively soft, so causes less damage than steel if the cage falls apart. It handles heat better than polyamide so brass-caged bearings can be re-used after removal by heating.

What do all the markings mean?

Bearing assemblies almost always have numbers on one edge of the outer race, inner race or both races . This number should represent the base bearing assembly type, with one or more modifiers. The 1971 BSA twins workshop manual has a section on the modifier markings. Siimilar sheets should be available from bearing companies.
The main modifers of interest for British bikes are:

C3 or 000  larger radial internal clearance
M machined brass cage located on the rolling elements
RS one "rubber" seal
-2RS two "rubber" seals
TBH phenolic cage
TNH polyamide cage located on rolling elements
Y pressed brass cage
Z one metal shield
-2Z two metal shields

Imperial and metric dimension

Items manufactured to Imperial dimensions (inches, feet, yards, perches, chains, etc) were usually dimensioned in multiples of 1/64 of an inch rather then hundredths. The dimensions normally come out neatly in eighths or quarters, with the very occasional sixteenth, thirty-second or sixty-fourth. Bear this in mind when measuring bearings with calipers or micrometers calibrated in decimal fractions of an inch. Once upon a time, calipers used to be graduated in sixty-fourths.
Items manufactured to metric dimensions tend to be made in decimal fractions of a millimetre


BSA Unit Singles C15, C25 B25, B40, B44, B50


Engine

Crankshaft




Drive side outer




1971 - 1973 (B50)

ball journal
1


Hoffman LS9


Drive side inner



1959 - 1973

roller journal
1


Hoffman
R325L


Timing Side




1959 - 1970

ball journal
1


Hoffman
325


1971 - 1973 (B50)

roller journal
1


Hoffman
R325L

Gearbox

Mainshaft




Drive side



1968 - 1973

ball journal 1


Hoffman 130


Timing side



1963 - 1973 (non-distributor models)

ball journal 1


Hoffman LS7 (L27?)






Layshaft




Drive side



1968 - 1973

needle roller 1


Torrington
B108


Timing side (kickstart spindle)




1968 - 1973

needle roller
1


Torrington B108
Clutch





Centre
3/16" x 3/16"
loose roller
25

Wheels

Front




Single-sided brake



1962 - 1969
7/8" x 2" x 9/16"? ball journal
2


Hoffman?
LS90R

single-sided brake



1968 - 1970

ball journal
2


Hoffman?
LS9RS


conical hub



1971 - 1972
20mm x 47mm x 14mm ball journal
2


Hoffman
120

Rear





QD "crinkle hub"



196? - 1970 (drum)

ball journal
1


Hoffman
LS9


hub

ball journal
2


Hoffman
LS9RS


bolt-on drum



196? - 1970
7/8" x 2" x 9/16"? ball journal
2


Hoffman?
LS90RS?


full width hub



1962 - 1965

ball journal


conical hub



1971 - 1972
20mm x 47mm x 14mm ball journal
2


Hoffman 120



Front end

Steering head
1962 - 1970
1/4"?
loose ball
40

1971 - 1972

taper roller
2


Timken
LM.11949L


Rear end

Swinging arm





1971 - 1973

needle roller
2


Torrington
B1616



BSA Pre-Unit Twins A7 / A10

Wheels


Rear
QD "crinkle hub"
195? - 1963 (drum) ball journal 1
Hoffman LS9
hub ball journal 2
Hoffman LS9


BSA Unit Twins A50 / A65 / A70


Engine

Crankshaft




Drive side



1962 - 1965



1966 - 1972 1.125" x 2.812" x .812"
(1 1/8" x 2 13/16" x 13/16" ?)
roller journal
1


Hoffman RM.11L


R & M MRJA 1 1/8


RHP
MRJA1.1/8J



only appears to be available in original RHP


Gearbox

Mainshaft




Drive side



1962 - 1972
1 1/4" x 2 1/2" x 5/8" ball journal 1


Hoffman 9554/V4


Skefco RLS.9 1 1/4



1654-2RS
 (remove inner rubber shield)


Timing side



1962 - 1972
3/4" x 1 7/8" x 9/16" ball journal 1


Hoffman L.38


Skefco RLS.6


R & M LJ 3/4
Layshaft

RLS6-2RS
(remove inner rubber shield)


Drive side



1962 - 1972
3/4" x 3/4" needle roller 1


Torrington
M.12121-OH



CS1212


Timing side



1962 - 1972
3/4" x 3/4" needle roller
1


Torrington B.1212-OH



B1212OH

Clutch





Centre
1/4" x 1/4"
loose roller
20

Wheels

Front




Single-sided brake



1962 - 1969
7/8" x 2" x 9/16" ball journal
2


Hoffman
LS90R

full-width brake



1968 - 1970
20mm x 47mm x 14mm ball journal
2


Hoffman
120


conical hub



1971 - 1972
20mm x 47mm x 14mm ball journal
2


Hoffman
120

Rear





QD "crinkle hub"



1962 - 1970




bolt-on drum



1962 - 1970
7/8" x 2" x 9/16" ball journal
2


Hoffman
LS90RS?


full width hub



1962 - 1965

ball journal


conical hub



1971 - 1972
20mm x 47mm x 14mm ball journal
2


Hoffman 120



Front end

Steering head
1962 - 1970
1/4"
loose ball
40

1971 - 1972

taper roller
2


Timken
LM.11949L



BSA / Triumph triples A75 Rocket Three, X75 Hurricane, T150/T160 Trident


Engine

Crankshaft




Drive side



1968 - 1977

ball journal 1


Hoffman LS.11

Timing side



1968 - 1977
roller journal
1


Hoffman R.125
Timing gear






needle roller
1


Torrington B.1110


Gearbox

Mainshaft




Drive side

1

1968 - 1977









Timing side

1

1968 - 1977








Layshaft





Drive side



1968 - 1977


1






Timing side



1968 - 1977


1





Clutch




shaft



1968 - 1977?

needle roller


INA
SC.228 1

thrust race




1968 - 1977?

radial roller
1


Torrington
NTA.2233

lever

ball journal


1968 - 1977?





Hoffman
S5


Wheels

Front




full-width brake



1968 - 1970 20mm x 47mm x 14mm ball journal
2


Hoffman 120


conical hub



1971 - 1973 20mm x 47mm x 14mm ball journal
2


Hoffman
120


disc brake




1973 - 1977


2
Rear




bolt-on drum



1968 - 1970
20 x 47 x 14 mm ball journal
2


Hoffman 120


conical hub



1971 - 1975
20 x 47 x 14 mm ball journal
2


Hoffman 120


disc brake




1975 - 1977


2


Steering head


1968 - 1977?
1/4"
loose ball
40

What goes with which?


The last BSAs were manufactured in 1973, so many of the bearings will be obsolete.
Most bearing shops will have excellent cross-reference charts, but it might prove useful to have some initial alternatives

Here goes...

Original Alternative

Manufacturer Bearing Manufacturer Bearing
Hoffman LS90R
Hoffman LS9
SKF / Skefko RLS7
RHP L J 7/8
R&M L J 7/8
FBC LS9
generic 1640
Hoffman 120
generic 6204
Hoffman 125
FAG
 (+ generic?)
6205
Hoffman R325L
NF305
Hoffman 325
generic 6305
Hoffman 130
generic 6206
Hoffman LS7
LJ 5/8"



There are some useful online cross-references as well

NSK bearing cross-reference

INA (FAG, etc)