Amos Todd 186

Might come to nothing but i would like to here about this motorcycle or even see a picture.


Trevor Amos wrote:
Hi,James,
Great info , could i have your bore dia please and can i assume standard dia crank and rod length values.
I hope i can help with a few observations based on my experience with the 4 speed 186 engine that was
produced by BSA , and , taken over by us from George Todd.

kind regards , Trevor



Kind Regards


Eddie

Hi Ed

certainly will , i`ll dig out some info and pass it on

Trevor

Hi Ed ,
Here we go then, the history as i know it , rightly or wrongly , is thus .
The whole machine was produced "in house" by BSA with specific items being sub-contracted to specialist firms . The concept was to produce a
testbed engine and compete in the Irish 200cc class , where the machine to beat was the Bultaco 196 , and QUB could offer technical input .
Derivative engines , for motocross and trials , were also to considdered , going all the way up to 250cc !

Cycle parts were the D5 frame , modified by Reynolds under the supervision of of Ken Sprayson . Twin down tubes , needed to clear the straight
out exhaust duct , ran from steering head to the swing arm pivot. Ducati forks and brake were fitted up front and the rear hub was a full width
job with large dia flanges and finning between . It was obviously Bantam but unseen at that point on a road bike .

On now to the engine. Crank cases , based on the D14/4 , were sand cast for strength and rigidity with inlet bosses cast in for a disc valve option
later . Bigger dia main bearings supported the crank . Cast in were small dia beveled crank chambers . The crankcase mouth height was
reduced in height and extra screw holes were included.
The crank , with integral shafts and plugged balance holes , was made by Alpha Bearings and featured a bevel for the , later intended , disc
valve. The crank throw was 62mm and featured a Bultaco con rod of 116mm centers with a bronze small end bearing . The piston was D14/4
plus .5mm dia Hepolite , giving a bore of 62mm , and a square configuration of 186cc . The standard piston rings proved fragile so were replaced
by steel ones we had made and proved to be faultless .
The gear box had four close ratios , and the shafts ran in ball races . Selector mechanism ,clutch actuation and body were all standard D14/4 ,
and the std clutch assembly, with extra springs, if looked after, proved to be adequate .
The cylinder head had two horizontal fins the remainder being vertical, it had considerably more fin area than a" George or Brian " option,
as a result the engine looked quite tall . A central plug featured in a hemispherical combustion chamber and the 50% squish band , of .8mm
clearance gave a comp ratio of 12,5.1! The engine ran very coolly and never holed a piston or deto`ed , the odd seizure could even be put
down to the waywood contact breakers . Oh, if we only had access to an electronic system in the 70s .
The alloy barrel was a real gem and a lot of thought went into it`s design and had a quality liner shrunk in . Ample transfer passage area
was featured with nice radii for controlled gas flow . Only two transfer ports though ! Efflux angles covered an adequate piston crown area
for bulk flow and cooling.
The exhaust port duct was dead stright out and down to a 41mm outlet , much too big but that was, again , 70s thinking . Pipe retention
was a castelated , screw in collar.

The carb was , originally, a 29.5mm TT but was soon upgraded to 32mm TT and a real improvement was felt from mid range to top , this
was one engine that was under carbed . The engine would rev all day to 10,000 rpm in the lower gears and peak out at 9,500-9750rpm .
The whole package was bullet proof but for the odd primary chain failiure , which , given it`s grunt , one could excuse . It also ran much
higher gearing than the current crop of 175s , 16t gear box sprockets for both Cadwell and Lydden .

It will always be part of the human condition to be wise after the event , that i regret parting with the machine , such a shame that it faded
into an historical footnote .
If anyone should get a whif of it , let me know post haste !

Regards , Trevor

ps , let me have your email address Ed and i`ll send you some more info and pics as attachments ----Trevor

Good Afternoon Trevor,


Just wanted to say thank you very much for taking the time to write all of that information, a very interesting read.

I have messaged you my email address.



Kind Regards



Eddie

Sorry Ed , hav`nt received any thing yet, have another attempt , If still no go i will contact you !

Trevor

Trevor I'm sure like me others are interested in this. Please don't pm photos and further info for Edwards own personal viewing. Please let us all have a look.

Good Evening Trevor,

It is still in my outbox so maybe your inbox is full possibly? I will leave it to you as to where to post the information so people dont feel i will be the only one seeing this.


Regards


Eddie

Good Evening Trevor,


I did try another mail but that didnt go either. Im sure when you have the time we will all learn a little bit more.


Kind Regards


Eddie

Courtesy & Property of Trevor Amos.

Hi Ed,
Gratefull thanks for that , hope you enjoy it all Ned , bit late , but Ed got us there !
I have a few more anecdotes connecting the BSA competition shop to QUB ,but have to assemble the papers to make a
coherent post ?

regards Trevor.

Fascinating! Thanks!

Hi Trevor,

Your welcome, glad i could help and thank you for sharing the photos and info with us.



Regards



Eddie

just been studying the photo's Trevor

photo's

1st a very youth-full looking Dave Amos, "he was always better looking" well that what he said! "taken at Cadwell-park no doubt about this.

2nd is more difficult, But Definately Trevor Amos, and either at RAF Watton or west Rrainham,? I \'m guessing! Watton because of the hanger in the rear

3rd one is Lydden "a guess based on hill in background".


regards Derek

I could be wrong but as far as i know it is as follows:


Pic One - Trevor Amos - Cadwell

Pic Two - Dave Amos

Pic Three - Lydden


Eddie

Hi all,
Spot on Ed, ten out of ten.
There you are Derek , i was really the good looking one all along !

nice chuckle though lads , all the best , Trevor

To be fair i had an unfair advantage, trevor named the photo's and i forgot to put the tags up!

An amazing piece of history and engineering.



Eddie

if Georg Todd was looking in he may have something to say on this !!

And "why is his name (amos Todd) missing of two of the photo's ?

The "GTD" 200cc is a low bike, did you not have issues with the exhaust touching.

Derek

Good Evening Trevor,

Apologies to adding to the questions,

Were the foot rest section and front brake popular to the era?



Kind Regards


Eddie

Read an interesting article today "Martin Hodder goes to... MEET THE BANTAM RACERS" featuring Trevor & David Amos.


Eddie

Hello Trevor - remember me? I've come back to haunt you all, 'cpt I'm happy to say in real life I'm so happy to see big Bantam I made is still going!!
It's all SO long ago now that I've forgotten the details of building that engine, but somewhere in all my paperwork there must be some info left.
I can see how important it is to set the record straight, so I simply have to find time for that The pictures you posted certainly helped recall some of it...

I'm absolutely astonished that Bantam Racing became so firmly established in the intervening years - after all, I can go back to my first race at Blandford
at Easter 1950. There was a young man Geoff Duke riding a quite new style Norton, the original Featherbed unveiled there for the first time I believe.
John Hogan easily won the 125 race in which there also 150cc 4-stroke JAP (or was it Blackburn?) running on dope - soon after 1950, dope was banned in road racing... I tried some in the Bantam at the time, but without a decent cylinder head I couldn't raise a high enough compression-ratio

So, like I said - I had better start raiding my archive for what there is left and perhaps do some writing
Until then, have a good day,
George Todd

Hello George ,
Oh , i most certainly do remember you , and could i , on behalf of all Bantam enthusiasts from around the world , welcome you to
the Bantam Forum . It seems like only yesterday that brother David and i first met you at Sundayshill Cottage , i felt a bit like a
gauche young novice being confronted by the mystical "High priest" but , you and your wife made us so welcome that the visit
was a joy .
I have a copy of an article you did for the Motor Cycling magazine and is dated June 1956 , that is a full 55yrs ago and here you are
still writing about our favourite topic , long may it continue !

We all eagrely look forward to more revelations and memories from what be your extensive archive and deep knowlege of all
things Bantam and , maybe , the Altair days !

Warm regards , Trevor

Hi all some more goodies from George

for some more info he is going through it and gradually loading to his face book page, I would suggest those with a face book page pop along to Georges page. some very intereting quotes/pictures.

George said:- on his face book page :-
The forks were from a Ducati model - this famous Italian firm was going downhill at the time (1970). But look at them now - producing fabulous bikes, Why the hell couldn't we have done that at BSA's? I'll tell you all one day, when I have time:-)— at Falfield, Glos.

George said :- My guess is that it topped the "ton" (100mph) easily... When I tested it, the acceleration was almost frightening:-) If only BSA's had progressed with this cylinder& head development for their most successful small bike. Instead, it was pushed aside for silly projects like a 3-wheeler for "Mum to go shopping". It failed.

Thank you George





regards Derek

Looks like the engine described in the Aussie Scott letter ?

Anyone wanting to build an Amos Todd replica - read this post lots of detail in it.

The only thing you will not find I fear is a 4sp close ratio box, but a D3 or D5 s/a frame should not be a problem.... one on ebay £65

"Mike"

4 speed close ratio Boxes have been available for some time now, these are redily available anyone wanting one can contact Rex Gaunt, I understand they run slightly different ratios to the Amos box.

but you need some std G-box parts to make up a full box, all readily available from Rex Gaunt Racing,

just ask Rex Gaunt he has had them made.

Derek