60's 5 speed Bantam racer

Came across a 31 March 1966 copy of the 'Motor Cycle' which has an article about a race winning Australian 5 speed, twin ignition serving a single plug, Bantam racer. Charlie Edwards, a head mechanic on a 46,000 acre station was the builder. He cast the head with a half moon squish band giving a compression of 16 to 1. Then he redid the barrel. After turning off the fins, he cast on a light alloy sleeve which was machined smooth on the outside. He then welded on the lower five fins to clear the ports before shrinking on the upper six. A standard Bantam piston was used which needed regular replacement!
The flywheels were lightened and a home made con rod fitted. The two ignition systems were a Villiers 7E flywheel magneto in place of the original, and a 12 volt battery and coil. The mag sparked first by 1 and a 1/2 degrees.
He cut the gearbox of a spare Bantam, inverted it and bolted it to the left of the main. The details of the machining are amazing. However, once he got into 5th he could not change down! I think his technique in now known as carrying speed through the corners!

Perhaps only used in Sprints...!!??

Hi John

You may well be right but I have re read the piece and the only ref to sprinting is that the bike turns a standing quarter in 17 secs. Vic Willoughby (the author) also comments that ‘unfortunately, as race day drags on the engine tires of bussing at 8 to 10,000 rpm and looses its appetite....choke size of the Amal TT carb is varied, according to the nature of the circuit. from1 and 1/16 upwards’.

I wonder if this remarkable engine is still around?

Jim

PS After re reading the piece several times I now have to apologize to all our readers for the confusion caused by my rush into print!

I now notice the fourth last paragraph reads; ‘What he (Edwards) does point out is that once he has selected the higher ratios in the auxiliary box he can’t get out of it without stopping to reselect the lower ones manually’ It then continues ‘However, not being able to select the lower range or ratios once he has changed into fourth doesn’t bother Edwards; he only uses the lower gears for getting up speed and is them content to ring the changes on the upper range.’

Ahhaa! Jimmie! your PS adds some sense. That was similar to riding Andy Boyle´s 250 ABS with 5 gears at Llandow. With the Bantam I´d use only 2nd and top, once away from the grid and with Andy´s 250 I´d have it in 4th and 5th only -- the circuit was really only two bends. if a portion of grass was used at Pits -- after starting in first, in both cases. Previous to that I had the gearing all wrong and wasted time changing up and down until my leg ached.
But back to sprinting -- I was wrong in any case -- Brian White said that with the 175 on sprints he´d only use 3 gears anyway: the third gear change took up too much time.
...
Pity really! I seem to be learning more about Bantam & two-stroke tuning than I ever did when racing... Perhaps it would have stood me in good stead when I tried to tune Icarus-2 to have had all the knowledge expressed on here.
I have excuses for that -- Derek Neil was a keen engine man and he took it all on himself, whereas I had a harrowing job taking up too much of my spare time, a family to care for and not much time for tuning and racing. In any case, as said before, I´d not intended to race Bantam -- it just happened....

Cheers!