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suitable exhaust system and gearing, the performance was acceptable at last.
Many of these engines had been sold by the time I joined Anzani, but the ‘fixes’
were not acknowledged or adopted straight away, and then only partially. The
final Dynastart units incorporated an extra needle roller bearing, but this was a
long way inboard from the cam, which still floated about a bit! Only one ring
expander was fitted to each piston, and that to the lower ring too! The Zenith
carburettor that was adopted, was not exactly the model I had chosen either,
and had one small, but irritating flat spot. The production cars were just
acceptable, and that was how the design was frozen. The original prototype
(‘OYE 20’) became the demonstrator, and as such was thrashed mercilessly by
all and sundry, but was still running sweetly when I left, much to the amusement
of the ex-JARC staff.
A flawed design then...?
I would not have described the air cooled Unitwins as exactly ‘a flawed design’. I
described the shortcomings of the engine that I installed in the JARC, but once
these had been rectified the motor ran well enough and gave good service. The
close spacing of the cylinders would have been a limiting factor if any attempt
had been made to squeeze much more power from it, but the performance
potential was severely limited by the tiny rotary valve induction system that was
incorporated into the centre main bearing journal, and so this was never a
problem. What astounded me about this unit was the complete cock up that had
been made when the Dynastart had been added, and that totally untried
engines had been sold in quite large quantities. The motorcycle engines were
OK but not very exciting. Perhaps, with new alloy cylinders and ‘normal’ piston
controlled inlet ports they would have become more desirable, but my
suggestions fell on deaf ears.
We'll leave it there for now. Thanks Peter, that was absolutely fascinating. I'm
sure all the visitors to the site will be very pleased to be able to read such a vivid
account. Some lovely memories, some fascinating detail and some talking
points perhaps we can revisit on another day.
On behalf of all our visitors can I say, good luck, keep well and come and visit
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