Congratulations to Facebook reader Bill Beebe, who correctly guessed this bike within 20 minutes of the post. Second prize to John Markley Frank who was first on the site itself. The engine is obviously from an Ariel Square Four, but this motorcycle is actually a Healey 1000/4.
photo from http://www.rescogs.com/2015/06/beautiful-motorcycles-at-concorso-deleganza-villa-deste/
Ariel stopped producing the Square Four in 1959, and by the late 60s some spare parts were becoming harder to find. George and Tim Healey were brothers based out of Redditch, England that started building replacement parts – by ’67 it was a full time business and they decided they could create a new-and-improved Square Four motorcycle. Starting in 1971, they sourced Egli-styled frames from Roger Slater, who had UK manufacturing rights, and then built bikes which were claimed to produced 10 more horsepower (up to 50hp) and weighed 80 pounds less than the old Ariel. For more on this bike, check out this article from Greg Williams. Unfortunately, the Healey was not much of a commercial success and according to Best of British Bikes
photo from http://www.classicbikersclub.com/gallery/healey-1000-4
If you can find one in good running shape today, expect to pay around $50,000…