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How to identify a genuine
"BSA 1948 D1 Bantam"

Foreword by Hans Kreuzen
I wrote this page to let enthusiasts know what a genuine 1948 D1 bantam should look like, I have seen so many Bantams for sale, claiming to be a 1948, but are in fact 1949 or even plungers that started in 1950,
Please note that I am by no means an expert on the early Bantams, But I hope that this page will identify all the small differences found on a 1948 Bantam.
The information and research was collected for my own 1948 restoration project and is to be used as a guide only.
I hope, that to the best of my knowledge, it is correct, but, please do not hesitate to have a chat on the "BSA Bantams Australia" facebook page or email me with corrections to improve this page, Email:paintdoctor@bigpond.com
I also would like to thank all of the people who have helped me with information, pictures and advice, a special thanks goes to Steve Walsh, dating officer for the BSA Bantam Club in the UK. and Steve Mitchell, owner of an unrestored 1948 Bantam survivor in the UK, Steve was a great help during my own 1948 Bantam restoration.




My own 1948 BSA D1 Bantam, with matching recorded frame and engine numbers,
This Bantam was dispatched from the BSA factory to Bennet & Wood Sydney on the 14th October 1948, and has been restored as close as possible to the original specifications.

Brief History of the 1948 BSA D1 Bantam:


The BSA D1 123cc. engine and frame, recorded as a "Machine" was introduced to the public in 1948 and was mainly sold for export to the colonies, including America. to help bring some much needed export money back into the UK after the second world war.


Before this, the first 5 months of engine production was for export only, and used to power the Swedish Monark M70 motorcycle, These engines where stamped with the UYD1-*** instead of the YD1-*** The engine design had been taken from the German designed DKW RT125 as part of the war reparations. The engine design was used by many other motorcycle companies, including the 1947 Harley Davidson S Model 125 lightweight, later models where named the Harley Davidson "Hummer" this engine kept the originally designed clutch, primary chain and gear lever on the left hand side, The engine proved itself, and with small motorcycles becoming ever more popular in Britain, BSA decided to build a complete motorcycle around the D1 engine, and in October 1948, the BSA Bantam was officially launched, the bike had telescopic forks, a rigid rear end, direct electrics, shovel front-mudguard and fishtail silencer. With the "three gears" lever on the right hand side for the British market and a maximum speed of around 50 mph, good brakes for the time and great fuel economy.
The 6 volt lighting was supplied by a 27 Watt Wico-Pacy Geni-Mag generator, direct electrics meant no battery, The engine has to be running for the main lights to work. A small battery was included to operate a smaller pilot bulb in the headlamp when parked. Ignition was supplied from the same unit, in the form of a simple Magneto; this also eliminated the need for a battery. The Smiths speedometer was listed as an optional extra.

The earliest written records start with the GPO bikes from September 1947, I do not know for sure if these where for Bantam's, as according to a Classic Bike Guide "GPO Bantams" article, It is in December of 1948, that the GPO telegram Service in the UK, initially order 50 bright red 125cc Bantams complete with leg-shields, bumper/crash bars and a first aid kit bolted on the side of the rear guard.



The Australia (P.M.G.) Post Master General started using the rigid D1 Bantams around 1949/50.


The BSA Dispatch Numbers:

The information below can only be used as a guide and are taken from the written records that survived, You need to understand that the early record books are damaged and in terrible condition, some of the very early records are lost for ever or unreadable, there also appears to be no date order, to the dispatch of new bikes. For example, the first engine that can be read is 153, with frame number 26648, it was sent to the US, but the date sent is missing.
The next record that can be read fully is 173 which was again sent to the US, with frame number 26933 in May 1950. and as a final example, engine number 314 with frame number 5294 left the factory in May 1949.
The earliest recorded machines (Bantam's) were the GPO Bantams, dispatched in September and October 1947, with engine numbers that start with YD1 18351, the frame numbers match on most GPO machines,
Next in the BSA dispatch records are the December 1948 engine numbers for the D1 Bantam "Machine" sold to the public and export, even thou all the literature shows the Bantam being official launched in October 1948, these machines start at engine number YD1 101 and frames numbers vary from around 102 to 36000, there is no consistency with the frame numbers what's so ever. Frame numbers where allocated randomly and are all over the place, it seams there was no order in the assembly, BSA just used the next engine or frame in line to assemble the next D1 Bantam motorcycle.
After all of the above confusing information , It is my personal opinion, that the early frame numbers with three numbers (YD1-***) would have to be the earliest frames produced. Final note to keep in mind: The prefix numbers started with YD 101, so a frame number like YD1-589 is actually YD1-488


The Early BSA 123cc Two Stroke Engine, Primary Cover and 3 Speed Gearbox:
Please note that there is lots of manuals and literature written on these engines and my aim is merely to briefly point out the subtle differences found on the early 1948 125 c.c engine.
In 1947 BSA produced the early 123 c.c. for Swedish export, they where stamped with the prefix UYD1-*** They proved to be robust and soon BSA decided to design a complete light weight motorcycle for this engine.
The early produced engine (Recorded) numbers used in 1948 will start with the prefix: YD-**** followed by four numbers. Unless someone proves me wrong, which I am sure they will, ha ha,
The picture shows my own engine with the engine number YD-1891.
Note that the engine numbers are stamped on the right hand side, next to the front engine mount and not the left, found on later engines.
The narrow finned 52 mm. bore cylinder barrel #90-1 with a 58 mm. stroke was used for many years, As well as the normal "No" top head gasket, "No" bottom barrel gasket was used on the very early engines.


The early engine casings Right #90-162 and left #90-163 featured oil lube holes, drilled to lubricate the crank shaft bearings in different locations,
Another noticeable difference is the use of fewer bolts used to bolt the two casings together, the pictures show the difference.


Another noticeable difference is the flat cast drive chain sprocket flange, later engines have a raised casting, note the extra casing bolt hole as well, on the later engine.
The early 1947 and 1948 primary covers #90-139 had a straight line instead of the BSA embossed logo found on the later engines.
The three speed gearbox has a chrome kick start lever #90-91 that is straight and not bent as introduced in 1953,


This picture shows the Gear pointer #90-93 that points to the gears over the waterslide transfer on the chain guard.


1948 Wico-Pacy Geni-mag generator:


The very early 1948 Wico-Pacy Geni-mag generator housing has a inspection round disc, held in place by a spring clip, instead of the two small screws used in late 1948 and standard in 1949.


The Wico Pacy Geni-Mag housing also had small imperfections like the thin HT lead mounting plate, and these where improved in the later type cast housings, See the pictures for the differences between the 1948 and 1949 alloy castings.
On my own 1948 alloy housing the serial numbers read: Spec: No: 1005 Serial No: 19273
The early flywheel for the 27-Watt Geni-Mag AC unit has no embossed writing cast on inside, unlike the later S55/Mark8 type that is clearly marked with the Wipac AC/DC,
Note: These two types of flywheels are not inter changeable as the later type has more magnets cast within the flywheel.
Another common problem is that most Bakelite HT pick-up's found, are cracked or broken,
I was lucky enough to buy a NOS one right here in Australia.


Fishtail Exhaust:



I went through all the trouble of ordering a new raw steel silencer from a UK manufacturer in pieces, so I could panel beat and metal finish the two plunger recesses, before welding it all up, before the chrome plating.


The chrome plated down pipe runs underneath the footrest, into a chrome fish tail "rigid" silencer, all the reproduced fishtail silencers are advertised as a rigid fishtail, This is wrong as they have the pressed indentations to suit the 1950 introduced plunger model.


Amal 261/001D Carburettor and Strangler:


The easiest way to identify the 261/001D model is the screw on thread float bowl top, instead of the later 1953, two screws top, used on the 361/1 model
Apart from the two screws, there is no difference between the two carbs.
The Amal 261/001D carburettor uses a Main jet: 75, Throttle valve: 5, Needle jet: 0-106, needle position: 2nd notch from top.
The zinc coated strangler has the Amal "cleaning instruction" water slide placed on the back.


1948 Forks, Head stock plate, Center stand and Rigid Frame:


The very early 1948 forks, use slotted head grub screws #90-5032 to hold the four brass slider bushes in place, These grub screws were still listed in the 1949 parts catalogue even though they stopped using them. No spacing steel tube were used, as found on the later models, the four grub screws were centre punched to stop them working loose. Towards the end of 1948 the brass bushes were silver soldered into position.


No rubber gaiters where used in 1948 and the fork seal end caps where of the zinc plated thin smooth type. I had my worn sliders forks hard chromed and machined four new bushes to suit.


The top 1948 triple tree plate has 37 mm. spacings for the handlebar clamps, This was changed to the smaller 32 mm. spacing in December 1949, the bottom Handle bar saddle clamps are cast alloy and the top clamp plates are chromed steel plate, full alloy clamps are used in late 1949.


The early 1948 rigid frame will have the frame numbers YD1 followed by three numbers, Note that some 1948 frames have larger numbers as there was no order in the frame numbers used, according to the hand written records. The letters "B" and "G" as well as a number "4" were found on my 1948 frame.


The frame also features a spring steel clip #90-4709 and support plate #90-4710 to capture the centre stand in the up position, the clip is mounted with two bolts to the centre down tube, In December 1949 a spring and "C" bracket was introduced instead. The early centre stand has a small gusset plate for reinforcement, in later years this was improved with a larger gusset plate as the stand would bent under all the weight.


Rim's and Tyres:


The steel 19" rims featured the stamped "Trade Dunlop Mark" and "Made in England" and were painted in Pastel green, The size for front and rear rims are 19" by 2.75 with 36 painted steel spokes, Chrome rims where introduced in 1953.


The original 1948 Bantam was fitted with Dunlop "Universal" tyres, these are no longer available and the tread pattern is not being reproduced.


Tank, Petrol cap, Guards, Chain guard, Toolbox, Luggage rack:

1948/ 49 petrol cap Late 1949/ 50 petrol cap

The 8 litre capacity tank has the petrol filler cap on the left hand side and uses a Ewarts push pull flat slide petrol tap with cork seals and a brass fuel line. The 1948 and early 1949 petrol cap is easiest recognized by the Castrol "XL" Essolube "40" engraving, the very late 1949 petrol caps have the Castrol "XXL" Essolube "50" engraving, The front deep valanced guard has a embossed raised section for the side painted registration numbers, the rear guard features the standard half valanced sides, as found on all the rigid rear guards.


My 1948 chain guard has a straight cut edge, I know of a 2 weeks older 1948 Bantam in the UK with the same edge, I find this very strange, as the later 1949 chain guards features a rolled edge instead.


The toolbox has two chrome screws to fasten the lid, this type was used until at least 1952, a single centre screw type was introduced around 1953. The luggage rack is very narrow and has no centre cross bar,
The later 1949-1953 parts catalogue lists two types of carriers. Without the bar listed as " Standard" and with the single center bar "Colonial" rack #90-681, the most common rack has two cross bars,


Paint, Pin stripes and Water slides used in 1948:
The first 1948 Bantam advertised was only available in Pastel green, The story is that a new batch of green was colour matched from the last batch, so this is why every Bantam is a slightly different green, The best way to find "your" original colour, is to look inside the brake drums or under the fuel tank.
The petrol tank also featured 2 gold pinstripes on the centre top and also a gold and red pin-stripe around the cream inserts. The story from someone working on the assemble line is that the dagger lined pin-striping changed in size depending on the day as a new brush was issued out on Monday's and come Friday was worn out, only producing a fat line.
The cream insert grew in shape and size over the later years, note that the 1948/49 cream inserts are very flat.


Note the picture of the original paint 1948 tank, The Maroon and not Red, water slide BSA logo on the tank was slightly different from all the brochures and BSA manuals front covers, After measuring the original 1948 BSA logo from a original tank in the UK, I managed reproduce and plot the logo for my computer cutter that is correct in design and size.
The famous Bantam chicken logo was introduced towards the end of 1949.



The 1948 bantam also featured the "clear backed" and not the later black backed piled arms logo on the toolbox and headstock, The green rear number plate bridge featured a gold BSA and pilled arms waterslide without the 125cc found on later models. The chain guard has a gold three position gear pointer water slide, The optional Smiths Speedometer use a 'Lightweight machine" Waterslide transfer, The strangler features a "cleaning Instructions" waterslide.


1948 Head light, Fluted lens and Wipac bowden cable lever switch:


Not many original alloy headlights survived, as the old batteries use to leak and corrode the alloy shell. The Wico Pacy Ref. number, #1-58 aluminium headlight uses the Wipac embossed, fluted glass lens.


The headlight rim together with the reflector and bulb assembly, is secured to the alloy headlight bucket by means of a hinge that is locate by two rivets, a spring clip held the headlight closed and a gentle pull on the rim, would open the headlight to service the globes and batteries.
By November 1948, the headlight still had the hinge fitted, but the locking clip was replaced with the common standard screw underneath the headlight, still found on all models.
The embossed Wipac headlight rim is made from alloy and is normally painted green, but it is shown on my bike in bare alloy as seen in 1948 sales brochures, I spent too much time straightening and polishing mine, to paint it now, ha ha.


The 1948 Wipac cable operated lever switch shows the OFF, FULL, DIP, PARK embossed script on the top diecast alloy plate, the 1949 switch is identical except for showing only the OFF script.


These pictures show the Wipac Bowden cable switch that is mounted to the battery holder plate, inside the headlight.
The cable runs from the headlight shell through the small hole underneath the speedometer, to the Wipac cable switch on the handle bar.


Tail Light and Number plate housing:
The small Wico Pacy Ref. number #1-59" small egg sized alloy housing with a single filament bulb holder that illuminates the number plate though the two cut out sections covered in clear plastic. The smooth, thin, red plastic, doomed lens is held in by the chrome steel rim that clips onto two lugs and is locked at the bottom by means of a small screw.


The tail light housing, is a pressed steel cup, behind the main number plate frame and some are held in place with two very small bolts and nuts and some are spot welded.

Mansfield Saddle:

Originally manufactured in England by Mansfield, Heathfield Road, Birmingham, the saddle's part number is #90-9001 Type 43
The seat frame has a straight "vertically down" front mount and is covered in a leatherette early vinyl type material, It has no stitching on the top of the seat like found on the Lycett type after market covers.
It also features a Mansfield badge that is riveted on the rear.


My own seat, re trimmed to duplicate the original 1948 Manfields cover, it's close but not quite correct.

Pictures of the Wrights and Mansfield seats that where fitted on 1949 and later Bantams

Tool kit, Grease gun and Tire inflator:



It is a great fun to search forums and places like eBay, to collect all the original tools that were kept in the tool-bag #90-9013 The original tool kit contained: Tecalemit Grease gun #28-4265 Dunlop tyre lever #90-9018 Sparking plug spanner #66-9132 Double ended spanner #EB259 Box spanner #65-9115 Box spanner Carburettor #90-9022 Exhaust pipe union nut spanner #90-9016 Screw driver attachment #66-9038 Combination spanner #29-9254 Tommy bar #29-9253 Rubber cable harness clip #66-9049 (Made in England embossed)
The Autoplas steel bodied tyre inflator #90-9010 mounted under the fuel tank was used to inflate the original Dunlop tyres no longer available now.


The optional Smiths Speedometer and Speedo meter drive:



When the speedometer was not fitted by the dealers, the standard "Top Yolk Plain Plate #90-5036" steel cover plate was fitted instead.
The "Optional extra" Smiths #S411 Type "D" Lightweight Speedometer, features a smooth housing in 1948 and was painted Pastel green with the "Light Weight Machine" waterslide transfer on the flat side.
The speedometer drive #90-6024 and speedometer drive plain washer #M101a are mounted onto the early small diameter rear axle.
The speedo cable #90-9020 is listed as 45 1/2" long


Original Running in Instruction Card and Riders' Instruction Book for your brand new Bantam:



This folded small "Card" was supplied when purchasing your brand new 1948 Bantam from your BSA dealer, It includes all the instructions for running the engine in and shows all the basic operating controls.


The small 1948 "Riders' Instruction Book" for the BSA Bantam, model D1 125c.c.two stroke, was also supplied, when purchasing your brand new Bantam from your nearest dealer, It shows everything you need to know on how to maintain, lubricate and service your new Bantam. Note that this booklet shown in these pictures, is the original 1948 book, it even shows the plain primary cover and it also covers the locking spring clip headlight.


1948 Sales brochure.

Unrestored 1948 D1 Bantams:
Anyone else out there own a 1948 Bantam? Please let me know.

This is Rick Charlesworth 1948 D1 Bantam, I believe this Bantam to be the oldest "unrestored" survivor in Australia, the frame number is YD1 470 and this Bantam was dispatched on the 29th Oct, 1948 to Australia.
This is Steve Mitchell 1948 D1 Bantam, this Bantam is the oldest "unrestored" survivor in the United Kingdom, the frame number is YD1 715 and this Bantam was dispatched on the 16th Nov, 1948 in the U.K.
This is Hans Kreuzen 1948 D1 Bantam, this Bantam was dispatched 2 weeks later than my restored 48, the frame number is YD1 639 and this Bantam was dispatched on the 29th Oct, 1948 to Australia


Restored 1948 D1 Bantams:
This is Hans Kreuzen 1948 D1 Bantam, I believe this Bantam to be the oldest "restored" Bantam in Australia, the frame number is YD1 589 and this Bantam was dispatched on the 14th Oct, 1948 to Australia.
This is Kevin Leek 1948 D1 Bantam, his rigid was dispatched from the factory on the 18th Dec, 1948 to the BSA Distributor in Lincs. U.K, it was first registered Jan 1st 1949. Kevin is the 2nd owner from new.


Unrestored 1949 D1 Bantams:
This is Hans Kreuzen 1949 D1 Bantam, this Bantam will receive a survivor restoration to preserve it's history, This bike shows all the new features found on the 1950 model, the frame number is YD1-25667 and this Bantam was dispatched on the 15th Dec, 1949 to Australia
This is Tim Whiting 1949 " PLUNGER" Bantam in the U.K. This bantam was dispatched in December 1949 and registered on the 1st of Jan 1950. The brand new plunger model was officially released in 1950, but this Bantam proves that BSA dispatched plungers in 1949,
Note that this frame number is only a 131 younger to my own 49 rigid, and the letter "S"(Springer) is missing in the frame number.


Restored 1949 D1 Bantams:
David's father This is David Birch 1949 D1 Bantam, this Bantam was purchaced new, by David's father and restored by David Birch, the engine has 70'000 original miles on the clock, with the original rings and bore, The petrol tank must have been replaced at some stage with a later right hand filler cap, this Bantam was dispatched in early October, 1949 U.K.
This is David Davidson 1949 D1 Bantam, this Bantam was purchaced as a basket case and has been fully restored by David him self. this Bantam was dispatched in 1949 U.K.


Some more Bantam pictures:
My own 1950 plunger and my 1948 rigid during it's restoration.
Another picture of my 1950 plunger.


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