Thankyou all for your quick and helpful replies yes the company recommended to me is indeed Armoto Ltd they are quite close to me as I am located in north Notts.Am still looking for a workshop manual for engine and gearbox which is a Burman unit with kickstart removed to accommodate the rearset gear...

I recently purchased a 500cc single cylinder Ariel racer. I was told it was 1952. It appears to have been specifically built for racing with a much modified frame and equipment. The engine appears to have good compression and looking through the spark plug hole the piston appears to be a hemi-spheri...