Tech stuff

Index:
Oil bracket for A65 machines
BSA Bearings

Oil bracket for A65 machines

Diagrams provided to guide fabrication of bracket to hold spin-on oil filter.

bracket

bracket1

bracket1a

filter2

 

 

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
  • slipper shells
  • balls
  • rollers

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

INA (FAG, etc)