The design for the Ariel Square 4 goes all the way back to 1931, soon after Edward Turner created the interesting new four-cylinder motorcycle engine formed from two OHC parallel twins. The design became known as the square four engine, and lent its name to this Ariel motorcycle. Turner had actually shopped his engine design out to other British firms, but BSA rejected it.
By 1953, the Ariel Square Four 1000 had already gone through a few revisions, and was formally known as the Mark II. The Mark II featured a 997 cc engine. Upgrades to the powerplant included separate barrels, a new cylinder head, and four exhaust pipes, which bumped up horsepower to 40. This enabled the Square Four to ‘do the ton’, even with a curb weight of 425 pounds.
Here are two examples of the Square Four – one a beautifully refinished Mk I, the other an original Mk II. The Mk I has had 5 owners from new, the most recent of whom added an hour’s worth of miles (up to the current 35,505) and then decommissioned the bike for display in his collection. This auction is ending soon, but find this bike for sale in a suburb of Vancouver, British Columbia with a BIN of $22,542
I’ve also got a Mk II for you – this one’s got 56,000 miles and is an unrestored, numbers matching bike with two owners. The motor was rebuilt 6 years ago, got some break in mileage, and was then put away for storage. With the exception of the tail light, this bike is original. It comes with some extras like additional pipes, a new battery, and the original saddle bags.
Find this Mk II for sale in Asbury Park, New Jersey with bidding up to $7,100 and the reserve not yet met