RP Excerpts

Simon Holyfield

1. Introduction

Many people, from our grandparents to our parents and to ourselves have been introduced to the world of motorcycling through some simple two stroke machine such as the BSA Bantam. For our grandparents, they were a cheap form of motorised transport; for our parents, they may have been their first venture in classic biking for they are simple and relatively cheap - they are an ideal first restoration project. But today, we live in a very different world – we have been brought up without very much experience or teaching of mechanical equipment, we may not have been taught woodwork, metalwork or even been interested in design & technology at school. But that is no reason to be excluded from the psychological, social, commercial benefits & enjoyment that can be found in the world of old vehicles.

This Restorer's Guide is written from the point of view of helping someone with very little or no mechanical knowledge who is new to the hobby, or who is attempting their first project. What books there are, seem to start with the assumption of a lot of presumed technical knowledge and they jump about from bike to bike.

Based on feedback from members, the BSA Bantam Club has commissioned this book: a 'restorer's primer’ that is geared at describing & illustrating all aspects of an individual's first full restoration and rebuild project. The book uses a plunger frame D1 Bantam throughout, being the one of the most numerous models Those of you who have managed to find a D3 or a rigid D1 will have no fear, for these words are for you too.

Those of you who have other three speed Bantams – and I am talking about the numerous D7s, and the less populous D5s are still catered for by the more general sections and the fact that the three speed engine design is very similar be it in 125, 150 or 175 form.

D10 and D14 four speed owners can learn a lot about their machines as well.

Of course, many of the techniques & technologies explained in the book are not solely applicable to Bantams –restorers of other lightweight two stroke machines will find plenty of interest in its pages and whilst the book has been published on behalf of the BSA Bantam Club it’s text is applicable to all as a first-rate introduction into the world of restoring classic bikes

I hope you enjoy reading it as much as I have enjoyed writing it!

Simon Holyfield CEng MIMechE Sheringham, Norfolk September 2013

2. Acknowledgements

Writing a book, as I have discovered, is quite challenging though very enjoyable. The key thing is time – seeing as I have a day job and a family & an energetic spaniel to entertain! This book has been in germination in various forms for many years, but would not have got off the ground if it hadn’t been for the efforts of Bryan Price at the BSA Bantam club, who worked hard to convince the club that it would be possible to achieve.

Most of the pictures that are used to illustrate this book came from my own D1 restoration; those that didn’t came from an appeal posted to the Bantam Club forum. Many, many members responded with offers of pictures to be used, far more than I could ever need. Additionally, a couple of people provided significant texts, notably John Kirk, who did all the proof reading, Phil Keast, who provided all the pictures for the carburetter rebuild, Ashley Gray, who provided all the pictures for the engine rebuild section, Peter Sturgess, who wrote the section on drum brakes, and Colyn Thomas, who wrote the sections on spark plugs, bearings and the section on rear chains.

Many thanks to you all:

• Bob Board, aka Cocorico

• Richard Mallet, aka Itma

• Howard Blakeborough

• Waterman

• Basil Smith

• Jess Steele

• Garry Whitehouse, aka Lone Wolf

• David Birch, aka Davidwb

• Michael Foster, aka Mikef

• Neil Chapman, aka D7-Silver

• Norvin

• Rick Howell, aka HowD1

• Dave Bevan

• Doug & Sara Brown

• Phil Keast, aka Cornish Rooster

• Stephen, aka Anderzander

• Gordon G. May

• Peter Sturgess CEng FIMechE, Engineering Inspiration Ltd.

• Steve at Progressive Classic Products

• Colyn Thomas, the Technical Officer of the BSA Bantam Club.

• Brenton Roy and John Nash of the Ariel Owners Motorcycle Club, for the Tyre Fitting Section

• Ashley Gray, for most of the engine rebuild pictures

Finally thanks must go to my ever loving wife Vicky, who has put up with my obsession with all things technical for so many years, who talks about me & what I do so proudly in our local and who gave me the space & time to get back into a hobby which I have loved since childhood.

3. Contents

4. Why do you want to restore an old bike? 10

4.1. How fast does it go Mister? 12 4.2. Tinkering & making them better 12 4.3. So what’s next?............................................................................................................................13

5. Bantam History 14

5.1. Post-War Scramble 14

5.2. The Beginning - D1 Bantam 15

5.3. More Power - D3 Major 17

5.4. A new frame – Swinging arm D3 18

5.5. More power – the D5 18

5.6. Corporate Identity – the D7 19 5.7. A Modern Motorcycle – the D10 & D14 20 5.8. End of an Era – B175 ..................................................................................................................21

6. BSA Bantam D1 23

6.1. Specifications 23 6.2. Engine & Frame Numbers 24 6.3. Production Numbers....................................................................................................................26 6.4. Changes by Model Year 26 6.5. Colours by Model Year 27

7. What to look for in a project bike .........................................................................................................29

7.1. Where to find it 29 7.2. What do I want from this restoration? 29 7.3. How badly is that broken? ...........................................................................................................30

8. Research 32

&

11.4. Using the Micrometer 66

11.5. Dial Test Indicator 68

11.6. Comparators 68

12. Threads 69

12.1. Thread basics – what we are trying to achieve............................................................................69

12.2. How to describe a fastener 69

12.3. How to measure a thread 71

12.4. Data Tables for Threads in common use 72 12.5. Fasteners & uses 77

13. Oils & Greases, Sealants & Other Fluids 81

13.1. Use...............................................................................................................................................81

13.2. Two Stroke Oil 82 13.3. Properties 82

13.4. Grades..........................................................................................................................................83 13.5. Additives 84

13.6. Standards 85 13.7. Synthetic oils................................................................................................................................86 13.8. Grease 86 13.9. Other Lubricants 87 13.10. Sealants .......................................................................................................................................87 13.11. Locking Fluids 88

14. Bearings 89

14.1. Roller Bearings 89 14.2. Lubrication 90 14.3. Common causes of bearing failure 91 14.4. Radial Internal Clearances...........................................................................................................91 14.5. Care of operating bearings. 91 14.6. Roller bearings fitted to your Bantam. 92

15. Workshop safety 93

15.1. Job Safety Analysis 93 15.2. Working Environment 93 15.3. Eye Protection 94 15.4. Ear Nose & Throat 95 15.5. Hand Protection 95 15.6. Feet 97 15.7. Your Back 97

16. Tools 99

16.1. Tools for Maintenance & Assembly 99 16.2. For More Adventurous Activities 99 16.3. Special Tools for Bantams 100 16.4. Standard Workshop Tools 101 16.5. Taps & dies 103

17. Stripping & Cleaning 109

17.1. Cleaning 109

17.2. Electro Cleaning.........................................................................................................................109 17.3. Cleaning Exhausts 110 17.4. Acid Cleaning 110 17.5. Getting it undone 111 17.6. Off to the take-away 111 17.7. Don’t throw ANYTHING away! 112

18. Fabrication..........................................................................................................................................113

18.1. General 113 18.2. Material 113 18.3. Marking Out & Pattern Making...................................................................................................114 18.4. Cutting 115 18.5. Cleaning Up 116 18.6. Bending......................................................................................................................................116

18.7. Welding 117 18.8. Brazing 118

Newcomers Guide to Restoration

19. Paintwork 119

19.1. Colour Matching 119 19.2. Colour Identification 119 19.3. Cleaning Paint off at Home 120 19.4. Outsourcing Painting 121 19.5. Powdercoat 122 19.6. Cellulose 123 19.7. Two-Pack 123 19.8. Rattle Cans 124 19.9. Brushing Paints 125 19.10. Lining 126 19.11. Cylinder Barrels 127

20. Transfers 128

20.1. Types of Transfer 128 20.2. What do I need and where do I put them? 128 20.3. Application 130

21. Polishing & Plating at Home..............................................................................................................132 21.1. Polishing 132 21.2. Outsourcing chrome plating 135 21.3. Plating at home..........................................................................................................................135

22. Engine & Gearbox 140

22.1. Description 140 22.2. Data 145 22.3. Preparation 146 22.4. Stripping & inspecting the top end 147 22.5. Inspecting the Big-end Bearing..................................................................................................150 22.6. Dismantling – Generator side 150 22.7. Accessing & Inspecting the Primary Drive 151 22.8. Dismantling the clutch & primary drive ......................................................................................151 22.9. Taking the Engine out 153 22.10. Splitting the cases 153 22.11. Inspecting & renovating the crankshaft .....................................................................................154 22.12. Removing the gears & gear change mechanism 157 22.13. Inspecting & Renovating the Gears & Gear Change Mechanism 158 22.14. Inspecting & renovating the crankcases....................................................................................159 22.15. Replacing the Crankshaft assembly 160 22.16. Reassembling the gear cluster & gear change mechanism 162 22.17. Reassembling the crankcases...................................................................................................165 22.18. Refitting the engine 166 22.19. Reassembling the Kickstart 166 22.20. Reassembling the clutch & primary drive ..................................................................................166 22.21. Refitting the gearbox sprocket oil seal and the rear chain 170 22.22. Reassembling the generator 171 22.23. Reassembling the top end.........................................................................................................171 22.24. Cylinder Head 172 22.25. Refitting the ancillaries 172 22.26. Adjusting the Clutch...................................................................................................................172 22.27. Rear Chain 173 23. Fuel & Exhaust Systems 179 23.1. Bantam carburetters ..................................................................................................................179 23.2. Air Cleaner & Strangler 183 23.3. Refurbishing the carburetter 183 23.4. Tuning & Repair.........................................................................................................................189 23.5. Modifications 191 23.6. Fuel 194 23.7. Fuel taps & lines ........................................................................................................................196 23.8. Fuel Filters 198 23.9. Exhaust Systems 198 24. Frames, forks & swinging arms .........................................................................................................201 24.1. Frame & Fork Design & Development 201

24.2. Fork Maintenance 202

24.3. Yokes & Head Bearings 202 24.4. Dismantle the Forks 203 24.5. Reassembly 205 24.6. Handlebars & Controls 205 24.7. Main Frame 206 24.8. Plunger suspension 207 24.9. Stands, Footrests & the Brake Pedal 208 24.10. Seats 211

25. Tinware 215

25.1. Fuel tanks 215 25.2. Mudguards 220 25.3. Chainguard 222 25.4. Number Plate Holders 223 25.5. Toolbox 224 25.6. Battery Carrier 225 25.7. Luggage Rack 226

26. Wheels 227

26.1. Removing & Replacing Wheels 227 26.2. Wheel Bearings..........................................................................................................................229 26.3. Wheel Building 232 26.4. Tyres 243

27. Brakes 253

27.1. Dismantling the brakes 253 27.2. Relining Shoes 253 27.3. Setting up the Brakes.................................................................................................................254 27.4. Fitting stop switches to direct lighting bikes 256

28. Electrics 257

28.1. Background 257 28.2. Generator Recognition 257 28.3. Issues for All Systems 258 28.4. Wico-Pacy Geni-Mag 265 28.5. Lucas Alternator 268 28.6. Wico-Pacy Series 55 272 28.7. Bantam Electrical Systems 278 28.8. Electrical Components 288 28.9. Wiring & Earthing 303 28.10. Modifications ..............................................................................................................................308

29. Instruments 315 29.1. Speedometer 315 29.2. Bantam Fitment 315 29.3. How it works 316 29.4. Speedo Diagnostics & Repair 317 29.5. The Speedo Cable 322 29.6. Speedo Drive Gearbox 322 29.7. Ammeter 323

30. Cables 324 30.1. Cables & Uses 324 30.2. Outer Casings, Nipples, ferrules, inners etc. 325 30.3. Buying Parts 326 30.4. Making up a cable......................................................................................................................326 30.5. Cable Management 331 30.6. Lubricating Cables 331

31. Assembly............................................................................................................................................333 31.1. Approach to Assembly 333 31.2. Assembling a Bantam 333

32. Road Test & Shaking Down 337 32.1. Riding an old bike 337

A Newcomers Guide to Restoration

32.2. Riding a rebuilt bike 337 32.3. Riding a Bantam 338

33. Accessories 341

33.1. Tool Kit 341 33.2. Leg Shields ................................................................................................................................342 33.3. Bumper bars 342 33.4. Dual Seats 342 33.5. Pillion Footrests 342

34. Maintenance 343

34.1. Maintenance Routine 343 34.2. Lubrication Schedule .................................................................................................................344 34.3. Fault Diagnosis 346 34.4. Crankcase Drain 352

35. Legal Stuff..........................................................................................................................................353

35.1. Know your Bantam 353 35.2. Insurance 353 35.3. The MOT 353 35.4. Road Tax 354 35.5. Getting it registered 354 35.6. Recovering the original numbers...............................................................................................355 35.7. Getting an age-related registration number 356 35.8. The Q plate 356

36. Helpful Information 357

36.1. Metric/Imperial Conversion Tables ............................................................................................357 36.2. Letter & Number Drill sizes 358 36.3. Recommendations for Parts & Services: 360 36.4. Bibliography 361

37. Hold Points 363

4. Why

to restore an old bike?

You’ll read, if you are into the classic biking world, of the phenomenon of an aging population in the movement. I guess that goes with a number of factors – one of course is the spiralling value of these old things we know and love, due to scarcity, publicity, maturity and the investment market; one is the fact that since cars have become so widespread in the last 50 years and recently so cheap, that there is less likelihood that a motorcycle will be selected as transport for the impoverished teenager and then of course as the era of mass produced British motorcycles becomes history for many of us, the retrospective longing for the machines we had in our youth shifts to machines from other countries.

One of the things Henry Ford & others finally took away from us when he gave us transport for the masses was the skilled artisan. Prior to the 20th century, furniture, ironwork, stonework, clothing was produced on a cottage industry basis by local craftsmen & women & this carried on until the industrial revolution. The advent of the production line mean that the skilled man, whilst still working with his hands was now working to a pattern dictated by others – the satisfaction of personal creativity had taken another blow, as it would as industrial methods progressed driven by market forces & the needs of a country at war. Now, few of us are engaged in technical roles – indeed we are no longer trained to use our hands in school

So the classic British motorcycle has much to offer those to whom Matchless, BSA and Francis Barnett are unfamiliar, just as Kymco, Lifan & Hyosung are to me. One of those things, of great importance to most of us, is the reestablishment of that connection between the satisfaction of our own handiwork and the thrill of speed in the open air, coupled with the increased confidence & self-reliance stemming from the knowledge that the machine that was once immobile & broken is now alive once again – you pulled it from that hedge, you collected those parts, and you made it into a machine that could go. You took it to the MOT man, and he rewarded you with a certificate that said ‘you have done well’ – and you rode it away, probably the long way home. Isn’t that better than taking it back to the shop for someone to repair, handing it back to you with a hefty bill and the feeling that you weren’t up to the job, and it cost you a day’s wages into the bargain? And what would happen if it broke down miles from home on a wet Sunday afternoon? Well maybe that is just my own need for constant back-patting coming out (call Dr. Freud!), but that satisfaction, for many of the folks in the classic vehicle movement is a very real part of the experience. Then, as Charles Ware proposed back in the early 1980’s with his book ‘Durable Car Ownership’ which dealt with the economic merits of running & repairing the Morris Minor, there are very real economic & environmental benefits to running older vehicles. Charles’ revolutionary idea was to treat the car as a long term investment rather than a consumable. It would not be used for a year or two, serviced once with new oil & replaced with a new one like a washing machine or vacuum cleaner. It would be systematically repaired, by a trained technician using newly manufactured spare

do you want

5. Bantam History

So if you are still interested, let’s start to understand how this little beastie came into the world. Despite the Bantam being considered the archetypal 'truly British' lightweight motorcycle outselling all others, it was in fact a German design. It’s commonly known, especially amongst Bantam enthusiasts, that the design for the machine was derived from the DKW RT 125, received as war reparations. But what does this mean?

5.1. Post-War Scramble

After World War II, in accordance with agreements made at the Potsdam Conference held between July 17 and August 2, 1945, Germany was made to pay the allied nations US$20 billion, mainly in machinery and manufacturing plants. In addition, in accordance with the agreed-upon policy of the de-industrialisation and pastoralization of Germany, large numbers of civilian factories were dismantled for transport to France and the UK, or simply destroyed.

Beginning even before the German surrender and continuing for the next two years, the United States pursued a vigorous program to harvest all technological and scientific know-how as well as all patents and many leading scientists in Germany (known as Operation Paperclip), which led, amongst other things, to the US space program.

In the end, war victims in many countries were compensated by the property of Germans that were expelled after World War II. Dismantling in the west stopped in 1950, though reparations to the Soviet Union continued until 1953.

DKW produced trucks and heavy equipment in Zschopau, in the former East Germany. Their name, Dampf Kraft Wagen, translates approximately to "Steam Power Vehicle". With the introduction of motorcycles, their acronym was popularly known as "Das

Kleine

At the

would have been particularly interested in the DKW designs, since their "loop scavenging" system, invented by Dr. Adolf Schnürle & patented in 1934, was vastly superior to other two-stroke technology and was equally applicable to diesel & petrol engines.

the

So, the DKW drawings, which would probably have been on rolls of linen back in the forties, would have been identified by some British or US engineers as intellectual property useful to the rebuilding allied nations and were made available to allied motorcycle factories by some mechanism. The same design went into production in at least two and perhaps four countries in addition to the UK. Harley-Davidson started producing their

Wunder" - The Little Marvel.

conclusion of World War II,

Allies

6. BSA Bantam D1

So as we said in the beginning, this book will focus on one of the most numerous of all Bantam models, the plunger-framed D1. This section looks at the data you are going to need in your research – performance, specifications, frame & engine numbers, year on year model changes &, all important, colours.

6.1. Specifications

The data in the performance tables is taken from contemporary road tests in the pages of ‘The Motorcycle’ or ‘Motorcycling’ magazines. Machine specifications are taken from BSA, Lucas or Wico-Pacy data sheets.

6.1.1. Performance

Speeds in Gears

D1, 1948 D1 Deluxe, 1950 D3, 1954

1st 21 mph - 27 mph 2nd 41 mph 37 mph 38 mph 3rd 47 mph 49 mph 51 mph

Acceleration 0-30 mph 6.6 secs 6.8 secs ¼ mile 45 mph 33 mph 48 mph

Fuel Consumption 20 mph 192 mpg 150 mpg 30 mph 160 mpg 179 mpg 128 mpg 40 mph 128 mpg 115 mpg 104 mpg

Braking 30-0 mph 27’ 6” dry surface 22’ 6” dry surface 36’ wet surface Weight/cc 1.34 lb. 1.46 lb.

10-20 mph 15-25 mph 20-30 mph

Acceleration

1st 2.8 secs (D1) 2.5 secs (D3) 3.5 secs (D3) 2nd 3.8 secs (D1) 3.5 secs (D3) 4.0 secs (D1) 3.5 secs (D3) 3.8 secs (D1) 3.4 secs (D3) 3rd 12.6 secs (D1) 6.2 secs (D1) 6.4 secs (D3) 7.6 secs (D1) 6.0 secs (D3)

6.1.2.

A Newcomers Guide to Restoration

8.3.4. Factory Despatch Records

Factory Despatch Records are held by the Bantam Club, the BSA Owners Club and the Vintage Motorcycle Club; these are typically microfiche photographs of the hand written records maintained by the manufacturers despatch departments. Typically they record the frame number, engine number and the receiving dealer, along with details of specification & any non-standard parts provided

Bantam despatch records are unusual in that they are listed by model and then engine number, which makes life interesting if you do not have the standard engine. Frame number batches are known for each production year, which, if you know the model of your bike makes life easier for the club archivist when he is looking for your frame in the despatch record.

Additionally, it should be noted that machines found faulty on road test passed to the rectification department and were despatch from there. These were usefully not recorded in the despatch record.

8.4. Manufacturers Sales Literature

These vary hugely through the Bantam years reflecting the society into which Bantams were sold. Early posters featured the village sub-Post Mistress puttering off the meet the Vicar for tea & scones; the earnest blazer clad fellow explaining the intricacies of his machine to a smartly dressed lady friend who’s itching to get back to the tennis court; later we have wannabe Ton-Up Boys, with leathers & helmets, being started on a race along the A406 by a strange creature in spotted pyjamas.

Useful, often heavily retouched for printing, many of these are artist’s renditions & not photographs of actual machines. The adverts were produced by the advertising department; sometimes well in advance of that year’s model being manufactured. So often the finish was a rough guess at what colours may be used, and/or just a product of the artists imagination.

To be treated with caution, reflecting the imagination which went in to their creation.

8.5. Other Machines

Most locations around the country have some kind of transport museum, when you can drag the family out on a Sunday afternoon to look at some old bikes. This can be a an easy way to see your machine in the flesh, as it will be when restored but be aware that the fact that it’s in a museum is no guarantee of originality.

Other possibilities include local enthusiasts who you might find through the owners club or the Vintage Motorcycle Club, old bike dealers, whom you might find advertising the back of your favourite old bike magazine.

8.6. Owners Clubs

Of course, the Owners club is where you are going to find the largest concentration of expertise on your chosen machine. You are going to find friendly folk who want you to take part in their favourite hobby, and who have encyclopaedic knowledge of the bike you are working on, and will be able to help you find rare parts or someone to make them.

You are probably going to find an active physical & online social network as well – from branch meetings, ride outs to local events & national & international rallies – you can commit as much or as little time as your lifestyle allows.

BSA Bantam Club Publications include this book, and the useful ‘Good Blokes Guide’:

A Newcomers Guide to Restoration

Have you ever needed a local specialist who can attend to the needs of your classic, or an MOT station that understands old vehicles? The Good Blokes Guide has been put together by our members recommending specialists in your area who can help! Currently, the Guide is issued as a printed version available to members and a pdf available online.

A further club publication is ‘The Masquerading D3’ which is an account of my own D1 restoration.

8.7. Forums

Last but not least is the fantastic Bantam Owners Club forum. Out there in the ether is a host of folks talking online about all things Bantam – post your problems, share experiences, maybe even find parts or a new bike – there is always someone to help you. Most of the pictures used to illustrate this book, those that are not mine, come from Bantam Club forum members. You will find it through Google or directly at http://www.bsabantamclub.com/forum. This is one of the most active motorcycle forums I’ve come across, and it makes the club friendly, supportive and above all accessible, day or night, across the world. Other motorcycle clubs should be envious.

A Newcomers Guide to Restoration

9. Recording & Planning

This section is about planning your restoration, and recording what you do – photos, blogs, financial management & managing the restoration.

9.1. Got it home?

Resist the temptation to take it to pieces, or to get it running! Whilst Bantams are not excessively vulnerable to long term storage, many bikes should not be run without careful thought and preparation, unless dire consequences are welcome in the home...

9.2. Identify your Bantam

Bantams do not use what is known as a VIN or Vehicle Identification Number nowadays. Bantams were recorded by engine and frame number in a register by the BSA despatch department (see section 8.3.4 of this book) and we can use the frame & engine numbers listed in section 6.2 of this book to figure out what we have bought.

Frame numbers appear in one of two places: stamped on the headstock, on the left hand side, or on the front frame down tube adjacent to the engine mounting lugs, again on the left hand side. These can be very difficult to see, especially if the frame has recently been painted (powder coat will fill up the shallow stamped numbers rendering them invisible) but persevere – you may have to take some abrasive paper to the paint to find the numbers.

Frame numbers moved from engine mounting lug to headstock in 1955/56, so make sure you know where it ought to be before you ruin the paint. You are looking for ¼” stamped letters & numbers. Remember, if you have no registration document for this machine, and need to reregister it, the DVLA will need to have evidence of the frame number.

Engine numbers are a little easier, if only because we don’t often fill up the numbers with paint. Up to 1953, the engine number was stamped around the front mounting lug, on the left. Later, the number moved behind the

barrel, under the carburetter, just beside where the chain guard is bolted

Lastly you may find various other numbers stamped or cast into your machine. Various frame lugs may have cast in part numbers; the Wipac generators have etched part numbers on the stator casting; the carburetter has a part number stamped into the flange; the crankcases have small 3 digit numbers stamped into their edges to identify them as a matched pair.

of this book may (no promises) tell you more

Look for all these – you want the information! The various sections

about these numbers.

A Newcomers Guide to Restoration

18. Fabrication

You will find, as you get into bike restoration, that sheet metal items are often damaged, missing, & hard to find. Bantams are fitted with many sheet metal parts – cable clips, number plates, and battery carriers – and lead acid batteries happily spill corrosive fluid especially if crude charge control systems are employed, and this results in rapid corrosion of your battery carrier. So, it can be very helpful to be able to make your own parts.

18.1. General

Sheet metal fabrication is pretty straightforward, needing relatively simple, inexpensive tools. If you have a jigsaw, a vice, and a drill you can make many things.

For the purposes of this section, we’ll look at fabricating a simple front number plate.

18.2. Material

Most parts you will want to make will today be made from what is called cold rolled sheet – sheet steel that has been rolled to thickness at room temperature. This comes in a variety of thicknesses, e.g. 0.6, 0.8, 0.9, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0 mm; In the past these were sold as standard wire gauge – 20 SWG (about 1.0 mm), 18 SWG (about 1.2 mm), 16SWG ( about 1.6 mm), 14 SWG (about 2.0 mm). Thicker materials are more usually referred to as ‘plate’ and are usually hot rolled (guess what that means), resulting in a blackened finished, rather than the shiny finish of cold rolled sheet.

You’ll use, potentially: 

1.0 mm or 20 SWG for things that don’t carry any load – like this number plate 

1.2 mm or 18 SWG for small clips & brackets 

2.0 mm or 14 SWG for larger brackets & things that are stressed – a battery carrier for example 

3.0 mm or 10 SWG, or thicker for things like the centre stand stop plate, the centre stand ‘C link’ etc

You can buy this stuff in a number of ways. If you have any industry in your neck of the woods you can usually find a steel fabricator to befriend – he will have lots of CRS knocking around (depending on his business) and may let you have some for beer money – if you are lucky he might cut it up for you.

The other option, which I quite like, is eBay. This is usually quite expensive but it can usually yield exactly what you want, and it is easy to get stuff sent to you.

A Newcomers Guide to Restoration

Then finally you can make the first cut. Try and guide the saw so that it cuts along the lines, but just outside the lines. You need to leave a little material to be cleaned up by the file, without having to file away of large amounts of material, and you need to be able to accommodate a little wayward movement of the saw.

18.5. Cleaning Up

When you have cut the shape out, it’s time to clean up the blank to the design you want.

Use a relatively coarse file (a bastard cut), and a vice to support the work. Put the work low down in the vice, to avoid the work moving about. Use the file to file across the work in the direction shown in the picture, along the length of the file, to bring the cut edges down to the drawn lines and ensuring that the edges are even.

Use flat files for the convex edges & straight edges; use half-round files for concave edges. Switch to a second-cut file to improve the surface finish

You can use the draw-filing technique outlined in section 16.4.2 of this book, to improve the finish on the edges. Try and produce clean, square edges to make the plate look like it once emerged from a West Midlands press tool.

Next job, deburr the edges. Use a second cut file, in the draw-file position, at 45° to the edges of the plate. Use it gently, to just remove the burrs and then to just break the edge into a nice smooth finish.

18.6. Bending

Sheet bending can be performed in a variety of ways depending upon the desired result. The battery carrier, for example, has a bend at the top that reflects the radius of the battery; the fold at the bottom is a much tighter

Figure 18-1 Vice jaws with angle section added to increase width

21. Polishing & Plating at Home

I suppose you could argue that a lot of the ‘restoration’ of your bike will come in this chapter, in that it is the replacement & renovation of the finish which is going to make it look new and shiny again, if that is what you want. Bear in mind, before you get too fanatical, that replacing an original sand cast crankcase with a shiny polished one, however glitzy, is not the way it came out of the factory…

21.1. Polishing

Polishing at home is something that will:

1. Save you a lot of money

2. Give you a lot of satisfaction

3. Take a lot of time

4. Make a mess of your Christmas jumper

It’s a pretty simple process as long as you are methodical about it. For this section I have some photographs of some Ariel parts to show you.

Now, polishing is a technique that smooths high spots from the surface of a part, such that the various lumps and bumps, and pits and troughs, become more uniform and better at reflecting light. In our minds eye, we might see a polish as a creamy liquid which might be faintly abrasive. In practice, there is little to choose between polishes and abrasives – it is a matter of the degree of ‘abrasiveness’.

Here is a 'before' shot of an Ariel Square Four engine, straight out of the van it was delivered in. This graphically illustrates why you need the abrasive - the creamy polish will never shift that oxidation:

The first thing you need to do with this is clean it, so go and take a look at chapter 17. Then, you need to take it to pieces, because you want to be able to handle the components and you want to make sure that the polished areas extended only as far as they did in the factory.

You will find that to deal with alloy that is aged like the Ariel timing cover shown in the picture you will need some serious abrasion. Figure 21-1 shows the Abrasive Compound Kit, which contains three mops and three grades of abrasive, from 80 to 300 grit from The Polishing Shop at http://www.thepolishingshop.co.uk/ . The products these guys offer are great value and they arrive very quickly.

22. Engine & Gearbox

The purpose of this section is to describe the dismantling, inspection and reassembly of the engine & gearbox. The section takes you right through the engine & gearbox unit strip, inspection & rebuild from start to finish, so there are no excuses for you newcomers!

22.1. Description

The single cylinder two stroke engine used in the BSA Bantam range did not change in its basic layout throughout the 23 years that Bantams were produced. It is designed with the air cooled, piston-ported engine in the same unit as the three or four speed gearbox, with a multi-plate clutch and an electrical generator. The engine is laid out such that the primary drive and clutch is on the right of the engine, rider facing forward, along with the kick start and gear change; with the secondary drive and the electrical generator on the left.

The 3 speed gearbox persisted until the D1 & D3 models were a distant memory, and beyond – the 4 speed gearbox did not appear until 1966, with appearance of the Pastoral, Bushman & D10 Sport.

22.1.1. Crankshaft

The engine is based upon a simple crankshaft, constructed from two cast iron flywheels, with sheet steel discs, retained by staking, used to reduce crankcase volume & increase secondary compression without increasing flywheel mass. These discs, often known as ‘stuffing plates’ were changed several times during the life of the engine as the original staking, which consisted of little more than dot-punched stakes over the chamfered edges of the plates, often failed to retain the plates with the result that they came loose and rattled.

Figure 22-1 Engine Cross-section

The timing and drive side main shafts were pressed into the flywheels using an interference fit; there is no keyway to locate the mainshafts nor is there any nut to retain them. The result of this approach is that if the timing side mainshaft is not pressed in in the correct position, the engine will be impossible to time. The drive side main shaft carries the engine sprocket, which is keyed to the mainshaft and retained with a nut and tab washer. The timing side mainshaft carries the flywheel for the generator, and the ignition points cam. The generator flywheel is keyed to the mainshaft and is retained by a nut, and the points cam is retained by a further key and a small screw into the end of the shaft.

The big end bearing consists of a machined crankpin, again pressed into the flywheels and retained only by an interference fit. The big end bearing consisted originally of a crowded roller bearing running directly on the crank pin; the rollers were provided with two washers to contain them and the connecting rod axially within the big end assembly.

The big end bearing assembly was revised to a roller bearing with aluminium caged rollers in 1958.

The connecting rod is manufactured from forged steel, and is of conventional ‘H’ section. The small end bearing consists of a phosphor bronze bush, pressed into position. This was later changed for a needle roller bearing, but not within the life of the D1 & D3 models.

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you will want to measure it across the bike (transverse) and in line with the wheels (longitudinally). You will find the worst wear in the middle of the piston stroke, in line with the wheels since this is where the piston exerts the most load on the side of the barrel. Use the table in section 22.2

Now is a good time to paint the barrel, so take a look at the notes in section 19.11.When you are done, put the cylinder head and barrel in a safe place and you can look at the piston.

22.4.3. Piston

To remove the piston, first remove one circlip using a pair of needle nose pliers, or a small screwdriver to lever out the circlip. Be careful, these can disappear at the slightest whim and are another reason that you must cover the crankcase mouth with rag! You can bin the circlip as they must not be reused – they are very cheap and you really don’t want it coming out in service. Push on the end of the gudgeon pin; it may slide out without further assistance but if it is stiff, use a hot-air paint stripper to heat the piston crown. After a few minutes heating, the aluminium alloy piston should have expanded more than the steel gudgeon pin, enough to free the pin. Wear some gloves to protect your fingers and support the piston as you push the pin out – you don’t want to be putting any side load on the rod.

22.4.4. Piston Rings

Now examine the piston rings noting that these are located in their grooves by means of small pegs which engage in the piston ring gaps. If in good condition, the rings will be found to present a uniformly smooth metallic surface over their entire peripheries, and if they are in this condition and obviously have a certain amount of "springiness' as evidenced by the fact that their free gap is considerably greater than the closed gap when in the bore they should not be disturbed. If on the other hand, the rings show signs of heat as evidenced by brown or more highly discoloured patches, they should be replaced by new rings, and in this case particular attention should be paid to the fit of the ends of the rings on their locating pegs in the piston ring grooves, and they should also be checked in the bore to ensure that they have an adequate gap

First place the ring in the cylinder bore in a position where it is clear of the ports and, making certain that it is square by pressing the skirt of the piston against it or a suitable bar of material of the correct diameter, examine the gap which should be not less than specified (see section 22.2) Having satisfied yourself on this point, place the ring in its groove on the piston and make certain that it is free without perceptible up and down play. If it is not free and the groove itself is clean, rub the ring down on a piece of fine emery cloth laid on a dead flat surface, using a rotary motion of the arm to ensure uniform pressure on the ring. As soon as ring is found to be free in its groove, wipe it absolutely clean and fit it into position.

Get your micrometer out (see section 11.4) or find an engine reconditioning centre to measure the piston diameter for you. You want to measure it at the top, in the middle and at the bottom, and you will want to measure it across the bike (transverse) and in line with the wheels (longitudinally). You will find the worst wear at the top of the piston, in line with the wheels since this is where the piston exerts the most load on the side of the barrel. Use the table in section 22.2

Check also that there is sufficient clearance between the inner portion of the gap and the locating peg in the groove. Do this by closing the ring in its groove by finger pressure until there is no gap, thus showing that there is clearance at the peg underneath. If the gap will not close, indicating that the steps are binding on the peg, ease the steps gently with a dead smooth file. If the piston has been removed from the connecting rod refit it, first putting a smear of oil on the gudgeon pin, not forgetting a new circlip to replace the one which was removed. The piston must be replaced in its original position i.e., with piston ring gaps towards the rear on D1 and the front on D3 engines.

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Then put a piece of clean rag over the piston and crankcase mouth and turn your attention to the bottom end

22.5. Inspecting the Big-end Bearing

While the cylinder is off you can test the big-end bearing for wear. Take a firm grip on the connecting rod and pull it upwards until the crank is at top dead centre. Then hold the crank in place – put the bike in gear - and with it in this position try gently but firmly to pull and push the connecting rod in the direction of its travel in order to feel whether there is any play. If the big-end is good, you should not be able to feel any play in this direction. It is usually possible to move the rod sideways, i.e. parallel to the mainshafts If you can feel any play in the up & down direction, you should be preparing to get the big end replaced by a specialist. This is not a job for the amateur, and requires special tools and a press to dismantle the crankshaft.

22.6. Dismantling – Generator side

Your approach to this work depends upon the extent of your problems – whether you are trying to sort out the generator, the clutch mechanism or to fully strip the engine. Those that are fully stripping the engine will have the top end off already and can lock the engine for flywheel removal using a rod through the small end eye; if you are just seeking to repair the generator or the clutch mechanism, you can lock the engine with the rear brake, chain and gearbox. If you plan to lock the engine with something in the small end eye, use something as large as possible such that the small end bush is not indented, and protect the crankcase mouth with small pieces of hardwood.

Dismantling the generator side begins with removal of the points cover (2 screws, 3BA). Remove the points cam (Wipac models) by undoing the 3BA screw and removing the cam with a pair of needle nose pliers. Watch out for the tiny key!

Disconnect the cabling from the wiring harness – you will probably have removed the HT lead already, but now you can release the generator cables from their bullets and from the cable clip on the toolbox, if it is still there. Remove generator stator by undoing the three ¼” BSW screws in their slots, replace the points cover for safe keeping and store it away safely.

The next step is removal of the flywheel (generator rotor) nut. You will need to lock the engine at this point using your chosen method. When you have done this you will be able to use flywheel extractor (see section 16.3.1) to remove the flywheel

Please, please do NOT attempt to remove the flywheel without this tool! You cannot fit an ordinary puller into the Wipac flywheel and you will damage the flywheel, the long spindly mainshaft, or both. To use it, wind the inner screw right out of the larger outer part and screw

Figure 22-5 Broken generator mainshaft

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engine – you are going to find some movement, and if you are really unlucky you may even be able to see light either side of the slide. You may be able to find a better, replacement or even new slide but if the body is worn, it may be necessary to find a replacement.

Check the needle, which does not have any marking but should be smooth and with no step in the taper. Check the clip holding the needle in the slide (Figure 23-16) – these are sometimes cracked and may not hold the needle securely.

Take a close look at the float. Shake the float – there should be no sound of fuel splashing about inside. If there is, you can release the soldered centre seam with a hot air gun, preferably at a distance – you won’t ignite the fuel inside but wear goggles and gloves. And NO NAKED FLAMES. Re-soldering is best done with a soldering iron – using a heat gun results in an excess of temperature in the air trapped in the float which will contract and suck the solder out of the joint, making it leak. Keep the temperature down and work around the seam gradually.

Check the needle is straight, and make sure there is no step in the tapered nose.

Have a look at the clip and the bolt holding the carburettor to the engine – make sure the thread is sound 23.3.5. Rebuild Rebuilding the carburettor starts with replacement of the two body screws shown in Figure 23-13. Use a 6 BA fibre washer on the feed hole screw.

Next, fit the needle jet into its threaded hole on the body, followed by the main jet.

Fit the jet cover with a new fibre washer. It’s easier to tighten this on the bike.

Drop the float into the float chamber, making sure the pin engages with the hole in the bottom of the float chamber. Reassemble the tickler into the float chamber lid.

Figure 23-12 Throttle slide location screw

Figure 23-13 Body & screws

Figure 23-14 Float in place

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Lower the float chamber lid over the float needle, and use a new gasket (see Figure 23-15 – you may have to make this yourself). Locate and tighten down the float chamber screws with shakeproof washers, or screw down the float chamber lid.

Next, take the needle and put the needle clip into the correct position on the needle. Drop the needle and clip into the throttle slide, with the open side of the clip aligned with the cable groove. Fit the threaded adjuster into the mixing chamber top, and pass the throttle cable through the adjuster. Take the throttle spring and pass it over the cable, and hold the lid and the spring in one hand. With the throttle slide in the other hand, compress the spring with your thumb and manoeuvre the free end of the throttle cable into the groove in the throttle slide until the nipple will slip into the hole at the bottom of the slide. You can then release your grip on the spring and the slide should hold it in place.

This whole sequence is shown in Figure 23-16, and you should end up with the spring seated as shown in Figure 23-17.

Next, you need to drop the slide into the carburettor body. A few things to watch here – first, as you pass the needle in, make sure it goes into the needle jet.

Next, make sure the cutaway is to the rear, away from the engine. This will put the groove in the slide to the offside of the bike and the cable groove also to the rear.

You can see the cable groove from the inlet of the carburettor body, where the air cleaner fits; no groove is visible from the engine end.

This sequence is shown in Figure 23-18

Figure 23-16 Throttle Needle

Figure 23-17 Throttle spring seated

Figure 23-15 Float Chamber Gasket

Once the slide is aligned with the location screw, it should slide home into the body. When it is fully down, you will not be able to see through the body past the slide. Now you can screw down the mixing chamber lid.

Operation of the throttle should have the slide moving smoothly up and revealing the needle, as shown in Figure 23-19.

23.4. Tuning & Repair

Carburettor issues can be rectified with the information in the following section.

23.4.1. Cable Controls

See that there is a minimum of backlash when the controls are set back and that any movement of the handlebar does not cause the throttle to open; this is done with the adjuster on the top of the carburetter. See that the throttle shuts down freely, but note also that Amal lightweight carburetters have no throttle stop screw. A fully slack cable will cause the engine to stop, since the throttle will be closed.

23.4.2. Petrol Feed

Detach petrol pipe union at the float chamber end; turn on petrol tap momentarily and see that fuel gushes out. Avoid petrol pipes with vertical loops as they cause air locks. Flooding may be due to a worn or bent needle or a leaky float, but nearly all flooding with new machines is due to impurities (grit, fluff, etc.) in the tank-so clean out the float chamber periodically till the trouble ceases. If the trouble persists the tank might be drained, swilled out, etc. Note that if the carburetter, either vertical or horizontal, is flooding with the engine stopped, the overflow from

Figure 23-18 Replacing the throttle slide

Figure 23-19 Slide partly open

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In either case, the pipe was clamped to a one piece silencer commonly called the fishtail. It was manufactured from two sheet metal pressings, closed over a fabricated set of baffles and seam welded along both edges such that it could not be dismantled. These silencers can still be obtained, built to the original specifications from Progressive Classic Products (see section 36.2)

The fact that these silencers could not be dismantled was more of a problem then than it maybe appears today. In the 1950s, two-stroke owners were expected to mix their fuel with regular engine oil, which resulted

in considerable unburnt carbon in the exhaust which naturally found its way into the exhaust and then into the silencer, which caught the carbon and eventually clogged to the point where performance suffered. The remedy was to fill the silencer with a caustic soda solution or to burn the carbon out with a torch, resulting in burns, discoloured chrome and plumes of acrid smoke coming from the shed.

Nowadays, we have self-mixing two stroke oils which do not produce unburnt carbon and silencer clogging is unlikely to be a problem.

Such hard times we live in…

23.9.2.

Torpedo Silencer

In 1953, the original fishtail silencer was replaced with a short tubular silencer with removable baffles that could be dismantled for cleaning. The first version was relatively short and mounted from a welded stud on the silencer to a hole in the rear section of the frame. All machines equipped with the torpedo silencer had the exhaust routed over the footrest bar.

The silencer was fitted with a detachable cast alloy end cap held in position by a single central acorn nut inside the exhaust opening. This is easily unscrewed and the cap and internal baffle removed for cleaning. Incidentally, the cone is the same colour as the machine – green or grey, though reproduction cones are usually black. The baffle is a stack of flanged, perforated discs welded to a tube. A long stud is arranged centrally within the silencer, and the baffle is located over this stud and retained in place by the end cap. The baffle discs are provided with a decreasing number of holes toward the rear of the silencer to dissipate the energy in the exhaust gas. All that was necessary was to remove the end cap & nuts, and pull out the baffle which could then be scraped clean or treated to a dose of caustic soda from your Mum’s kitchen or the blowlamp from Dad’s shed.

Decarbonising this baffle then was a simple process and, in the days before modern 2-stroke oils arrived was recommended to be carried out at regular intervals of about three thousand miles (5,000 km.). The symptoms indicating an excessive deposit of carbon are roughness of the engine and a tendency to pink under load, erratic running with excessive four and eight stroking, and an appreciable falling off in power. This is particularly

noticeable when the exhaust port becomes fouled with carbon as it causes an obstruction to the free escape of the exhaust gas, and interferes with the correct scavenging of the cylinder which is so necessary for the efficient transfer of combustible mixture from the crankcase.

This short torpedo silencer remained in service until the demise of the plunger frame D1 in 1963.

The appearance of the swinging arm D3 in 1956 removed the opportunity to mount the silencer on the rear of the frame, and the silencer had to be changed. This brought a longer version of the torpedo silencer, with the mounting stud mounted much further forward and a considerable increase in the length of the taper leading into the silencer.

The end cap and baffling arrangements were similar to the short torpedo.

Figure 23-23 Long Torpedo on Jess Steele's lovely D5

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24. Frames, forks & swinging arms

This section is here to tell you what you need to know about your frame, forks & rear suspension. It gives details of design and development, inspection & repairs, bushes, stands, seals, springs etc. head bearings, and seats.

24.1. Frame & Fork Design & Development

Bantam frame development was rather conservative during the life of the D1 and D3. There were essentially two frames, both very similar single loop designs with either a rigid rear end or, after 1950 a simple plunger type rear suspension. At the time plunger suspension was a common modification since the factory could provide rear springing whilst maintaining the front half of the frame common with the cheaper rigid bikes and without having to alter chain runs, wheel offsets or braking systems. A significant redesign occurred in 1957 when BSA offered a swinging arm rear end for the D5.

Pillion footrest lugs appeared on all frames in 1953.

Fork development was a little more complex. Initially BSA offered a sprung, undamped telescopic fork with upper bushes fixed to the outer, sprung tubes and lower bushes retained by threaded closures. These were changed to fully removable bushes in 1951.

Gaiters were added to the forks after initial production batches. The bottom yoke was cast iron with conventional clamps retaining the fork legs; the upper yoke was pressed steel. The fork leg trapped the top yoke with a large nut, which held the top of the spring in its centre with an adapter retained by a nut.

Initially the outer tubes were parallel; in 1954, for the D3, larger diameter fork tubes were introduced, swaged down below the bottom fork yoke to use the same diameter unsprung legs The top yoke was changed to a casting and the upper sprung legs had a turned taper which fitted into a matching taper in the top yoke, making the whole assembly much more rigid. The springs were similarly retained in the top nut – using an adapter in the top of the spring which passed into the top nut and was retained by a standard nut, though this time the nut was hidden behind a plated cover.

The unsprung legs were in all cases chrome plated and carried a coarse thread at the top which screwed into the springs. The unsprung lower legs changed in 1954 when the mudguard was moved from its original mounting place on the upper fork tubes to an unsprung position, mounting from lugs welded to the lower fork legs.

At the same time, the headlamp bracket which had been a simple folded affair mounted off the bottom yoke clamp bolts was deleted and changed to a more elegant pressed metal cowl, welded to tubular shrouds which surrounded the fork upper tubes.

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clamp nuts with the tabs in position and push any wire loops well back behind the working faces of the stator legs to prevent them from fouling the flywheel.

Replacement of the Condenser

To change the condenser it is necessary to lift the stator as before described, and disconnect the lead from the terminal post and unscrew the clamp nut which is located on the contact breaker cover spring post. When replacing, make sure that the condenser lead is pushed down as far as possible into the well formed by the stator housing otherwise there is a danger of the flywheel rubbing and possibly severing it.

Replacement of the Flywheel

The robust construction of the flywheel reduces the possibility of any faults on this unit to a minimum. The three powerful magnet inserts are cast in the rim of the wheel and it is not possible to demagnetize them by ordinary usage. No keepers are necessary when the magneto housing and stator are removed. The boss of the flywheel is located on the crankshaft by a keyed taper and locked by a nut and shakeproof washer. It is unnecessary to remove the flywheel unless at any time the engine has to be dismantled. A thread cut on the outside of the flywheel boss enables the wheel to be removed by use of a special extractor. When replacing, the flywheel must be perfectly clean inside and outside.

28.5. Lucas Alternator

The Lucas 1A45 was fitted to some 5000 deluxe machines until 1953, with a complete Lucas lighting, ignition & charging set.

28.5.1. Description

The Lucas Model 1A45 unit, which has a nominal output of 45 watts, consists of a 6pole laminated steel rotor and a stator comprising two permanent magnets, a laminated field system and two coil windings housed in an aluminium casing.

The rotor, combined with the contact breaker cam, is bolted direct to the engine crankshaft.

The alternator body, which carries the stator coils and contact breaker plate, is spigotted into the crankcase. The contact breaker plate is located by two fixing screws passing through radial slots, (B in Figure 28-7)

The condenser is of normal Lucas design with a capacity of .2 microfarads, fitted to the points back plate with a screw, and connected to the points terminal as shown in Figure 28-6.

The principle of operation of the induction alternator is the same as that of other generators, that is, the reversal of magnetic flux through the coil core which generates a voltage in the coil winding. In the normal generator, the reversal of flux is achieved by rotating either the magnet or coil, but in this design the coils and magnets are stationary and a laminated steel rotor is used to cause the flux reversals.

Figure 28-7 Lucas Alternator

Figure 28-6 Lucas 1A45 Generator attached to a Bantam engine

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The rotor is of 6-pole design in order to give as many flux reversals as practicable during one revolution. Thus the windings are stationary, so avoiding the use of commutator, slip rings or collector brushes, making for greater robustness of construction and hence increased reliability.

The generator reaches its rated voltage at a low engine speed and the voltage is then maintained within close limits over a very wide speed range.

Electrical Performance

In addition to supplying the current required by the lamps (Lucas equipped machines have an increased headlamp bulb wattage of 30 W), the 1A45 unit also supplies power for the coil ignition equipment.

At the time, there was a long standing objection to coil ignition on motor cycles, the inability to start if the battery is run down. This was overcome by the provision of an "emergency start" switching facility which temporarily disconnected the battery so that all the available energy from the permanent magnet alternator was applied to the coil, with the result that a slow speed performance approaching that of a magneto enables the machine to start

Battery Charging

Since batteries can be charged only by direct current, a Westalite Selenium metal rectifier is incorporated in the system, and all components then run off direct current from the battery source, two plates are used in the rectifier assembly to provide full-wave rectification in conjunction with the centre-tapped generator. The rating of the rectifier plates has been thoroughly investigated both in temperate climates, and in the high ambient temperatures of the Middle East. The rectifier is of robust construction and is sealed against water ingress, making it suitable for mounting in a semiexposed position where it will receive adequate air cooling. With this equipment there is no need to fit a cut out as the reverse current through the rectifier is very small, and is a negligible drain on the battery. To avoid even this slight drain, which is very little more than the usual surface discharge across the top of the battery, the ignition switch is arranged to disconnect the battery and alternator when the ignition is switched off. The ignition switch has three positions: "Off," "Emergency Start," and "Normal Start." "Emergency Start" position enables the engine to be started and run with a flat battery. The alternator has an ample margin of safety but should not be run with the battery removed and/or the ignition switch in the emergency position any longer than is necessary.

Figure 28-8 Westalite Rectifier

Note: Switch off the "head" and "pilot" lamps before starting the engine with the ignition switch in the "emergency start" position. Failure to observe this precaution may result in blown headlamp bulbs. Immediately the engine is running turn the ignition switch smartly back to the normal running position then switch on the "head'; or "pilot" lamps as required.

Two Charging Rates

Reduced charge switching is coupled to the lighting switch so that full output is obtained from the generator only when the lamps are switched on. During day running a reduced charge resistance is inserted into the circuit. Since the excitation is by means of permanent magnets, the wattage output for a given speed is limited and a higher battery voltage results in a decrease of charging current rather than an increase, so that the system is to a certain extent self-regulating. The lighting switch is similar to the standard Lucas U.39 motor cycle lighting switch and provides positions for "Lights-off - Half charge," "Pilot and Tail lights and Full charge," and "Head and Taillights with Full charge."

Performance Data

Full charge output is 7-10 A; Half-charge output is 5 A, of which 3 A is available for battery charging with lights off, the rest being used for the coil ignition. The alternator will commence to charge the battery at 600 engine revolutions per minute and maximum output is attained at approximately 2,000 r.p.m and is substantially maintained to maximum engine revolution.

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28.5.2. Routine Maintenance

Maintenance is restricted to occasional inspection and lubrication of the contact breaker parts, and normal routine attention to the battery. No adjustment is necessary (or possible] to either alternator or rectifier.

Contact Breaker Assembly

Every 1,000 miles (or monthly, whichever is the lesser period) remove the contact-breaker inspection cover for inspection of the contact points. The contacts must be free from grease or oil. If they are burned or blackened, clean them with a fine carborundum stone or very fine emery cloth, afterwards wiping away any trace of dirt or metal dust with a petrolmoistened cloth. Reset contact-points to .010 - .012ins. A few drops of good quality engine oil should be applied to the cam lubricating wick if it is dry. Place a small amount of grease or clean engine oil on the contact-breaker pivot.

To remove the contact breaker, unscrew the contact-breaker base fixing screws, and then lift up the contact plate complete with the condenser. The position of the contact-breaker base relative to the alternator body should be noted and marked to obviate the need for resetting the ignition timing on reassembly.

Ignition Timing

Ignition timing is not critical to the successful running of these engines. Minor adjustment can be carried out while the engine is running. To advance the timing, slacken the screws retaining the contact breaker back plate slightly rotate the plate in the opposite direction to the rotation of the flywheel.

Figure 28-9 Lucas 1A45 Generator

Bulb horn

28.8.5. Ignition coils & Rectifiers

The parts listed in Table 28-2 are shown here. Use the model numbers shown in the note column for reference.

Switch Notes

Lucas CQ, used 1950 to 1953 on Lucas equipped Bantams.

Mounted beneath the tank on a welded bracket.

Clearhooters HF150 From 54 parts book. Listed in grey and green

Switch Notes

28.8.6.

Batteries

The batteries listed in Table 28-2 are no longer, or very rarely available new or in a usable condition and so you are looking at using a reproduction or perhaps original battery case to hide a modern battery.

The tall Lucas 5 Ah or 9 Ah and Varley Mc5/9 batteries were used in a wide variety of bikes including the Triumph Tiger Cub as well as the D1 & D3 battery lighting Bantams

These boxes are often made from a pattern moulded from an original “Lucas" battery in fibre glass or polyurethane material, which looks very similar to the original ebonite

Lucas Westalite rectifier

SenTerCel Selenium Rectifer

SenTerCel Selenium Rectifer from 54 parts book

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casing. They are around 85-90 mm square inside, and around 150 mm high, so you will need to source a battery of suitable voltage & current rating that will go in the box. Many battery suppliers list the dimensions for this purpose, but it is worth noting that using a gel battery will enable you to have a wider choice as these batteries can be fitted in any orientation.

28.9. Wiring & Earthing

Bantam wiring harnesses are relatively simple, as can be seen from the diagrams in section 28.7. You can buy a wiring harness new, or you can build your own. This is particularly useful if you want to modify the harness, or if you are concerned over the quality of the harness you might buy. If you make the harness yourself, it’s guaranteed that it will fit.

28.9.1. Wire Selection & Sheathing

During the 1950’s plastics were beginning to appear in vehicle electrical systems, and the PVC covered cables used in vehicles until recently is quite suitable and is still available.

Table 28-3 shows some likely wire sizes that can be used in our bikes. Wire sizes can appear a little peculiar; but reflects some useful elements of the cable. The cable is manufactured from stranded copper conductors, and the size describes that. ‘14/0.30’ describes 14 strands of copper wire of 0.30 mm diameter. The corresponding total cross sectional area of the conductors is 1 mm2, and the diameter of a cable of this size for the typical automotive low voltage application is 2.7 mm. The current rating of the cable is shown in Amps.

More modern vehicles use a thinner wall, higher performance insulation with more, but thinner copper strands for a given cable size. This allows the weight of the wiring to be reduced, and allows the cable to carry a higher current load

Table

28-3 Wire Sizes

Wire sizes OD Configuration Rating Application

1 mm2 2.7 mm 14/0.30 8.75 A 2 mm2 3.4 mm 28/0.30 17.5 A 3 mm2 4.2 mm 44/0.30 27.5 A Shown for speedo lamp in 1951 owners manual 4 mm2 Shown for rear lamp in 1951 owners manual

Sheathing was provided by a characteristic woven cotton layer when these bikes were new, which is impossible to replicate in the home workshop. If you want a standard harness with this sheathing, you will need to source one from a Bantam parts supplier.

Sheathing options for the home harness builder include PVC tubing, a woven plastic mesh tube or traditional harness tape (which has no glue layer to get messy).

Woven sheathing expands & contracts to fit your harness, and is not too dissimilar to the cotton braid sheathing. Branches can be made neatly by bringing the wires through the wall of the braid; the ends are bets terminated by a short length of heat-shrink sleeving.

Period harness were also manufactured using rubber tube, which can be replicated using PVC sleeving which is readily available in a range of sizes. A branch is shown in the illustration in Figure 28-16, showing a break in the main harness, sleeved in a large tube, and a branch sleeved in a much smaller tube.

Figure 28-17 Dipswitch harness in woven sheathing

Figure 28-16 Main harness in PVC tubing

34. Maintenance

Easy maintenance is one of the great things about old bikes – but I guess none of you need convincing of that. No electronics, no hydraulics, no cooling system, no fuel injection and it is all so accessible you can do the work in minutes. I carry a head gasket in the toolbox, since I failed to torque the head down properly once and yes, I have had the head off by the side of the road!

The following sections describe how to maintain your pride and joy once you have it up and running.

34.1. Maintenance Routine

Most of your routine maintenance tasks are covered in the lubrication schedule in section 34.1.1. Those that aren’t are listed below. For this section, it is important to have identified your bike and particularly which generator it is fitted with. See sections 9.2 and 28.2 Service

55 28.6.3

28.4.2;

Electrical Lights Functionality

Stop Light Functionality

Every time you ride

Check every time you ride; adjust brake light switch as necessary

Ammeter 29.7

Lamp details –see section 28.8

Lamp details –see sections 28.8.2 & 28.8.3

Stop switch adjustment – see section 27.3.2

Horn Every time you ride 28.8.4

Battery Check fluid levels weekly if you are using a lead acid battery; modern regulators will require less frequent battery maintenance

34.1.1. Fastener Security

28.8.5

It’s important to regularly check the various nuts, bolts and screws that hold your bike together, especially after a rebuild. In practice there are relatively few different hex sizes, so it’s a simple matter to go over your bike periodically and check that nothing is coming loose.

After a rebuild, there may be things you have forgotten in your haste to get it going and a 15 minute exercise with the spanners can prevent disaster. Paint, especially powder coat, has some flexibility and fasteners will bed down and loosen off. You will find, if you repeat this exercise every few weeks that you have nuts that regularly loosen, and nuts which don’t. This is a part of learning about how your bike behaves, and you can modify your maintenance regime as you become familiar with it.

34.2. Lubrication Schedule

Items in the lubrication schedule in this section refer to the pictures below:

Newcomers Guide to Restoration

And help comes from the strangest places sometimes – my wife, who has no interest in motorcycles, is very good at asking how the broken thing is supposed to work, in minute detail. The result of me patiently explaining how it works usually results in that Eureka moment – when you finally figure out what’s broken.

34.3.1. Starting & Running

Note that symptoms which cause poor running, excessive fuel consumption or poor starting are very similar and one will rapidly lead to another. Look at all the symptoms and read the whole section before starting work.

Symptom Cause Remedy

Poor starting Condenser failure, often accompanied by pitting at the points

Points poorly adjusted or faulty

Disconnect the condenser and measure the resistance to ground. This should be very high – a low resistance here is the most likely culprit. However, condensers also fail open circuit, showing an infinite resistance – so substitute your failed sensor with a new one.

See section 28.3.3

The points should be gapped correctly, and should open with a small spark

Ignition coil faulty Coil windings have a pretty low resistance generally; sometimes difficult to measure when the meter’s accuracy is taken into account, so you will need to accurately zero your meter. The primary resistance will be a few ohms at most.

In a flywheel magneto, the primary winding is earthed at both ends whilst the points are closed. Behind the stator, fastened to one of the stator mounting studs is a tab which earths one end of the primary and the secondary. The other end of the primary coil is the wire attached to the black plastic post, to which the points spring is attached; if you detach this wire from the post and measure the resistance to ground you should get the true resistance of the primary.

Measure the resistance of the secondary (HT) cable to ground – this should appear on the meter as an immeasurable (low) resistance

Poor magnetism

The traditional answer is to find somebody who can remagnetise the generator rotor; today, permanent magnet rotors are much less common and the machine required to re-magnetise the rotor is a rare thing. Use the internet & the club forum to see what you can find, or perhaps consider a replacement rotor – either original equipment, or consider an replacement, modern generator (see section 0)

Retarded timing

Faulty spark plug

Adjust ignition timing – see section 28.3.2

Check your plug by removing it, lay it on the cylinder hear and kicking the bike over – you should see a nice fat spark. Make sure the plug is clean and there are no carbon deposits evident between the electrodes. If in doubt, replace the plug but again, you must not use a resistor type. See section 28.3.5

If there is still no spark, test the HT lead and the cap.

Faulty HT lead

Check your HT lead – it is a copper core lead isn’t it? You must not use a modern carbon core lead!!! Test the lead using the method shown under ‘faulty spark plug’ above.

Faulty plug cap

Check your plug cap using the method shown under ‘faulty spark plug’ above. You must not use a resistor type plug cap. If in doubt, remove the plug cap and connect the HT cable direct to the plug, without a cap, by baring some copper and