New member and Bantam build

Hi all, my name is Louis and i am a 15 year old kid from New Zealand. I have been interested in motorbikes for a while and i have recently built a board track racer replica using 2 villiers midget engines. I have been given a 125cc Bantam project and i am planning to make it into a racer.
The main criteria is that it has to be road legal so i can use it for transport as well as racing.

Here are some pictures of my board track racer first









And here are the pictures of my bantam project









I would love all the tips and suggestions i can get

Hi louis

looks like a great little project you got going there, !!! you may find some people with some limited knowledge will not answer you, as your in another country and not able to swell our ranks, so they may not be interested in you, but I will answer ! If i were you, I would look at George Todd's new book, and check out his facebook page (the book "shoe string racer") he will mail it directly to you. it has loads of very interesting information about his liife, and the BSA Bantam he raced and developed, and then passed on to others, some say it's out of date and old hat. but to my mind its the methodology and simple changes that makes up development, to eak out a remarkable level of power and reliability, I have followed a similar - during my return to Bantam Rcaing, after many years away. Its taken two year of development with a lot of help from Uk stallwarts of the Bantam cause people like Alan Brown", a fast rider tuner himslef, and "Trevor Amos" exhaust man, and lots of hot air, lol. and "Tom miller" gearbox mod man and the london Brotherhood chairman, assistant to all at race meetings, all really helpfull guys, sadly you dont have these in your race paddock, but they do come on here well two of them do, all they do is help others, sadly Tom Miller does not post, but he does talk through others.


I now have a very, very, very(windup) fast and resonably powerful Bantam, Im also also "very modest" about this.

With the right rules or rider It would be a winner, but because Iam not the rider Iuseto be, or the current rules, that so need changing" that favouse small bhafron statures, ("light weight riders), sadly like many I'm in middle age now and just not as light I I was in my 20's, to do the bike justice.

but I am getting there and last year often surprised a few, and for sure when Iattend any mettings I willsurprise a few more, as you can no doubt read I try to make up for this, "when I get the opportuninty".lol.

The sad thing is Ihave not been able to drill home this cense of fun, in my son who had intended to race, in the same class, he was put off by a very poorly placed dig at me. About the legality of his Barrel (but we are over this) he spent 12 months maticulasly polishing ports, changing direction and making sure it followed a good coander effect by bolting it to a margarine tub with smoke pellets and a valume cleaner on the exhaust, this took months painstaking work, finally building his engine, but comments about it's legality on here put him off for life.

Reading between the lines, you can see there are indeed lots of friendly leg pulling, some look at the funny side, but others can not see this as they had a transplant from Birth of their (personalty bypass) so dont be put off.


Looking at your stuff, you have a really old D1 cases with an early narrow fin barrel, Your cases that are good- same as my current race engine, unike others, I worked in the foundry where they cast these for BSA, a lot more material on the walls of these cases, than on later d1,d3,d5,d7 sand cast types, especially around the main bearings wall face material, was /is 2mm thicker, every one goes for the D7 sand cast cases but contrary to popular belief by one cam these are not the strongest, especially for a 175cc the die cast cases are much stronger for this clastt, well unless you intend to weld or over do the transfer entry by taking out too much metal to get a bigger transfer barrel, on it. I have only ever used the D1 cases as a result of the extra thickness, there is a lot more material on them, so I feel you have a good base.

if you have three holes on the right side crank as you look at it, on the internal drive side face, then this is the only way you can tell they are the correct type, more importantly I see you have a plunger frame, my dad (who built my engine before I was born) and now at the ripe age of 79 has just completed his rolling chassis, I was at his house yesterday, preparing for the comming race season, my gooodness its cold in his shed, we have some really nice new cranks, our own piston a two piece product with some extremly light and top secret materials, that just look amazing, also it not new as Itried it in the 80's it works, but stopped using due to other issues, Dads sprinter "also has a plunger frame" to be used, just for sprinting, we have been busy and have built a few options for our engines, development of our new Race motor has been going really well, its giving me astronimical Torque, one could only dream of, the HP at 22 is still a bit low but as I only had 18.9hp last year and about max 11ftlbs at a race meeting although its very easy to wind this upwards staying reliable is the only way, to close to the edge, I see its just time before I have 30hp and 20ftlbs, but I can not wait to try her out on the track, if your on face book check out a very close friend of mine, his name is Lar's but his face book name is !!! BSA BANTAM RACER,!!! contrary to some beliefs "he is a nice guy and real", ! he has many pictures of plunger racing Bantams on his page, sadly he came across to the uk to work and help me in a business venture, only here a few months we organised for him to have a ride on my Racing Bantam at Mallory park, he dropped it in the rain, considerable damge, to both him and the bike that I,m still only just finding.! he's gone back to Denmark, where he was fired for his inabillity to work, he is back to work now. "what a wonderful world we live in". Lars is still in touch and is also building a racing Plunger Bantam, he purchased two close ratio gear boxes from me, with some other bits and peices, and he is planning to come across to do the festival of 1000 bikes when its all finished.

Im sure you have so much to read here, lots of very good info from home page too, finally there is also a guy in your neck of the woods called "John Senddle" he has a few bikes one from the UK, one was a real fast bike in its day.

sadly I dont do tips "like most racers "I'm tight", But I will give loads of suggestions, you just have to work out which one's apply to you.

very best regards Derek, "the reformed"

Hello Louis ,
Welcome to the Bantam racing Forum ! That is one very sweet machine you have constructed there , if that level of expertise is shown in constructing your Bantam project , it will be a stunner .
Any questions you may have , no matter haw trivial you may feel they are , then ask away , someone is sure to give you an appropriate answer .

Keep us all informed with a progress report , Regards , Trevor

Thanks for your replies Derek and Trevor. My frame needs repairs as the result of a frontal crash i think. Is there any information about head tube angle as i am going to have to replace some areas of frame joining to the head tube.

Hi Louis!
Wow!

That Villiers Flyer -- it really looks fantastic. Slick tyres and no brakes. I´d really like to have a go on that on a dirt track.

Have you calculated the stored-enegy of those two flywheels?

And what a vast space to lay out all your bits?

Keep in touch,

All the best,
Cheers!

John-Boy.

Hi Louis
PM sent. Check to left of ‘log out’

Jimmie

An excellent piece of work.
I have sent you a personal message.
cheers
John

It looks like my bantam has had a frontal accident at some time in its life. The head tube has been pushed in at a funny angle so i am going to have cut the head tube off and weld in some new tube. What is the headtube angle for a D1 bantam? or should i put more rake on it?

Hi Louis Your Board tracker looks great your standard of work is impressive for anyone, are you sure your 15? I was pleased to see John has contacted you and if you want it he can give you my SKYPE name, I will be happy to have a chat. Your workshop looks fit to kill for and pleeeease will you let me know what’s under the big white sheet. It looks long with a drum front brake, I did think that it looked like 2 bikes under the sheet but I can only see two wheels. Good luck and best wishes with your project.
Smiffy.

Hi Ted, Yes I am am quite sure that I am 15! Hiding under the sheet is my dads aero engined Riley 9 special.

I have got all the suspension set up and together. I am going to get it rideable first and sort out all the problems and then strip it down for a full restoration.








I have also been putting the engine together and I will hopefully have it running tomorrow. I have also penned the 2 flywheel covers in. Do these make much difference to the performance of the engine?

I have had some progress on the bantam recently, first up I have made some little clip on's out of steel tube. The actual bars are just tacked on at the moment until I decide that this is the angle i want on them.







Secondly I have brought what I think is a very good thing, its an early 1960's Benelli drum brake. It is a full width, finned, cast alloy bit of Italian stuff. My plan is to spoke it into the bantam rim so I will have good braking performance but without having to put Japanese parts in it.

Not sure I'd weld the clipon like that, end on , most are cut out with a rad matching the clamp tube that way you'll get a greater weld area, they look very wide like that too , eye up some of the photos of some current racres you'll see just how narrow they are.

Agreed Dan but better then the brazing job I saw that had failed. Just a thin streak  of braze -- and not all the way around --
with a lumpy,thick "collar"    that could have  fooled any scrutineer -- but not the one I saw ...  I was present when this scrupulous  scrutineer thumped the end of the Clip-On and it fell off.

The rider was most upset and threatened the Scrutineer with violence ....

Sorry! I probably said this before.....
..

There will still be a good weld area around the tube, I imagine it would take a huge force to break them off. They still need cutting down to a shorter length.

I have got the engine nearly all together and ordered a 20 thou oversize piston kit from rexcauntracing. When that gets here I will get the barrel bored to match. How many thou clearance should the piston have in the bore?



I got the flywheel ignition all assembled with a new crankshaft supporting bush that I turned on the lathe. It makes a good spark which I am very pleased about.




The tires are from Peter Woodend. They are 2.75/19 Duro ribbed.



The rims and rear hub parts have been bead blasted, primed and I have painted them with topcoat. The color is Ceramco blue.

Not I get what this is, is it mostly for the road? The rear hub is the early type, apparently these are not good enough to take the stresses, I learnt that one early on, also the clipons do need changing ,sorry to keep on, its not only for strength in physical terms but the vibrations tend to crack things like clipons and lower rear frame near swingarm mounts .

Hi Dan, I am building this bike to be a "racer" not that i think it will be very competitive because i am only a 15 year old with a very basic knowledge of tuning 2 strokes. I have been reading all the 2 stroke tuning books I can get my hands on so experimenting with tuning of the bantam engine should give me some good experience!

Good to know about that rear hub, where about's do they fail? This would be good to know.

You do seem very adamant about the clip on's haha but I am not convinced. I don't see how welding them on in front of the clamp tube would get any more weld area than doing it how I have done it, wouldn't the only plus be that the bars are further in front so you could stretch out more?

`Scuse me butting in, Dan and BoardTracker ...
I think it is a matter of quality of the weld, BoardTracker. I brazed mine on and to avoid what I had said before -- that there was insufficient braze between the two,  extended  the brazed-contact length by cutting the clip-on-tube in a U shape (plan view), bashing out the "ears"  and then bending the "ears" out and round the larger, clamp-tube. This was so that the brazing started at  roughly the centre-line (neutral-axis), forward and back, of the clamp-tube. Made twice the length of brazing that way. I have seen other arrangements where the clip-on tube is shaped in a long curve to be forward -- or rearward -- of the clamp-tube which also extends the length of weld toward the neutral-axis*** of the clamp tube.

I did this -- not because I didn´t trust my brazing (I did) -- it was  because only about two months before I made my Clip-Ons ,  the (Swiss International) Sidecar Champion, Camaithias AND his passenger were killed at Brands Hatch because of such bad brazing.
That was  when the plate holding both the gear lever and the rear brake pedal  broke away from its brazing onto the frame. The scrutineers made a big thing of it:    showing that only a pencil-thin line of braze was holding the plate to the frame  -- and not all the way around.... Imagine approaching a bend at high speed and both your gear lever and brake-pedal are suddnly floating about in the fresh air!!

Like I said earlier, I saw a scrutineer break off a clip-on by just thumping the end of the Clip-On. Racing is dodgy enough without adding to its hazards by bad welding/brazing etc....

*** I expect you both know this already but it is now the opportunity to point it out to all ... Whether it matters or not that the weld or braze starts on the Neutral-Axis of the clamp-tube for Clip-Ons is unknown to me but where welded-in reinforcement-fillets & webs are made in frame construction they should be welded along the (bending-direction) neutral-axis of both tubes. A single web welded into the curve will eventually crack due to vibration as Dan says. i.e. As I say now; Two thin plates -- either side -- welded to the centre lines (neautral-axises) of the two tubes may not be stronger than a corresponding thick web but the resistance to failure by bending is much more than a single web-plate....

But there it is, BoardTracker. If you trust your butt-welding and you are going to ride/race the machine --. then why not?  But a GOOD weld should be good-enough...  

...hopefully!

CheerS!.

the picture will help, if you see the length of the weld is greater and the area larger when the handle bar is scoped out and matched to the clamp tube.  it may well be okay how your doing it, not seen it done like that before only the way in the picture and guess its for strength and joint integrity .

the hub you have is pressed steel rather than cast iron, it has riveted sprockets rather that screwed on type , this is what i was told  when building mine

"No one uses the early hubs for racing (too dodgy and difficult to use), and yes there is a better location area for the sprockets on the later D7 onwards type of hubs. They are generally fairly easy to obtain from ebay etc, make sure that the bolt threads on the new style go right though to the back of the hub (do a re-thread) and your sprocket screws (we use Allen head type 1/4 bsf thread) just show at the back of the hub with the sprocket fitted. This way you get maximum strength and there will be no breaking of the casting where the screws go through."

Yes Dan, that´s it. Even doubles up on the way I have seen some clip-ons. And those you´ve shown can be turned over so that the clip-on is behind the clamp-tube.

What´s the cost of that snazzy pair of SES Clip-Ons?

Cheers!

i think they're about £60 or so.

Thanks Dan... that´s 20 quid more than I spent on making Bantam, Icarus-2. But then Icarus-2 was made up of lots of bits I already had -- like a close-ratio gear set -- bits of kitchen ware and road-going tyres etc... etc... hanging up or laying about in the garage.

Thing about this Icarus-2 Bantam was that I experimented with the frame and front-end steering geometry to get conclusive results during practice at Brand´s -- which could be disconcerting at times. It "Flopped" into corners and was hard to get upright but once one got used to that -- it was fun to ride. Great Intermediate-Level-rival Collin, Wobbleyman Aldridge reckoned it was dangerous but he still raced it at Llandow when his own Bantam blew its motor to bits and was actually lying second when Icarus-2 also blew its motor -- yet again.... Reliabilty factor was almost nill!

That´s a thing to mention about The Wobbleyman: his bike went kaput during a meeting and someone lent him a big Triumph to race in an Allcomers event. When he got it back the owner couldn´t understand why the twist-grip was almost upside down -- obviously Wobbles had tried to screw the whole Clip-On off to get more from the motor.

Perhaps a good reason for proprietary Clip-Ons -- with lots of weld/braze length!!!


I am amazed at how much bits and things cost these days and know it is no use thinking about it. Beer was less than 2-Bob a pint at one time ....

As I mentioned on here before -- probably many times -- I got into Bantam cum road-racing by accident but I would not have missed it for all the tea in China -- even though it was only 5 and a bit seasons....

Keep at it!

Cheers,
JayBee....

Those are a very good looking pair of clipons Dan that I would love to buy, the whole point of this project for me though is to try to make everything and do everything I can on the bike myself spending as little possible money on the way!

I will keep an eye out for one of those hubs, they sound like a good thing.

As I asked before, does anyone know what the piston clearance in the bore should be? I have ordered a 20 thou oversize piston kit so when that comes I will need to get the barrel bored to the right diameter.

John, When you say that you experimented with the steering geometry were you cutting of the head tube and welding it on at different angles?

hello, i wasnt suggesting buying, i meant make yours like them, never buy!! god thats a dirty word, buy  

the piston bore thing, normally the clearance is on the piston already , so the bore would be whatever it is plus 20 thou.

Hi BT...!
No no -- never buy -- if you have welding gear and can get on a lathe and other machines there´s enormous satisfaction in the making of...

BUT I KNOW YOU KNOW THAT ALREADY... there´s something about being an "engineer" though --  that 95% of civilisation do not know -- that is, "An engineer can make anything, and make it work for a few  cents that any other dumb cluck needs scores of dollars to make the same...."
That was roughly  what USA´s President Hoover said in 1923 ....

I´d advise taking note of what has been said by a good expert on Ride & Handling on here Mick Potter*** who is an expert on such and has scribed some useful info on here about suspension units front and rear. You have to remember that it is better to start off with something that is recommended  as "normal" for racing so that you have a Norm to compare with.

I see you have plunger rear suspension and whilst a lot of Early Bantam racers used this -- including the successful, Australian Walsh Bantam  -- everyone seems to have moved on to proprietary suspension systems since then....

If you look back thro´some of my posts on here you should come across a couple of drawings of what I had done to the geometry of Icarus-2 -- if not I´ll get our Edward Pickering to re-post it for you. It´s all to do with what some call "Centre-Point Steering" or some such name. It is that a line drawn  through the steering head NORMALLY bisects the rolling radius at about 1/2" ABOVE the the halfway point of the RR. i.e. the line bisects the RR at less than halfway on the Rolling Radius down from the spindle to thé road.... The experiment I tried was having the bisection a 1/2" below... which meant the radius of gyration of forks-and-wheel weight was increased. Along  with this is also the deceleration forces (on braking) of the total weight which also acts to develop this FLOPPING.

An expert later said it invited the "High Sider" so I suggest you don´t go for it unless you are going to race on grass or board....    

To all intents & purposes it is NOT recommended. It was just a silly experiment that on a more powerful, higher speed racer would be disastrous.

I heard from Wobbleyman who had taken over both my Bantams when I went to Canada that Icarus-2 had been fitted with OTHER front forks. Probably fell off a lorry....!

Point of interest about modifying steering head angles I saw two fantastic frame breakages during my Grass Track days. Both failed at the down-tube just below the steering head. One  at a Grass meeting and th other at Rye House on a grass-trackers practice day. The first was a rapid high-sider where the down tube  broke
and the engine dug into the earth. Rider OK --      just a bit annoyed. The second was Syd Jervis who came out of the bend and slowly sank into the cinders with the wheelbase getting longer.

Both these frames had had their rake angle modified. Both had a single web -- welded in-- from top-tube  to down-tube which showed buckling before fracture of both web and down tube.

I think that backs what Dan said about víbration stresses being severe and although the road gives a smoother ride the frame does go through a lot of stress during racing.

I´d be interested to hear more. Are you going in for Board Trrck racing young man?  It is something I never tried and would have loved to give a go.

Silly question that -- you are using Clip-Ons ....??

*** I corrected the name later -- apologies to Mr Coombs and Mr Potter.

Keep with it,
#Cheers!