This is from the site Bring a Trailer (https://bringatrailer.com/) ...
This 1952 Ariel Square Four is powered by a 997cc OHV four-cylinder engine paired with a 4-speed gearbox. Finished in black and silver with gold pinstriping, the bike was reportedly refurbished in the UK before being imported to the US under previous ownership. The seller has added more than 400 miles since acquiring the bike in 2012, and notable service performed within the past 75 miles included engine and carburetor rebuilds as outlined below. This Square Four is now being offered with parts receipts and a clear Missouri title in the seller’s name.
Ariel produced the Square Four in various iterations between 1931 and 1959. This example comes from the fourth year of Mark I production and was repainted during the refurbishment. Closeups of the brightwork and finish on tank, fenders, and frame are provided in the gallery below. An imperfection is noted on the passenger pillion seat.
The suspension system is comprised of a telescopic front fork and Anstey-link rear suspension. Chrome rims wear painted centers and matching gold pinstriping.
Charging is managed by a Lucas generator, and an ammeter is mounted just above the 120-mph Smiths speedometer. 11 miles are shown on the odometer, and actual mileage is unknown.
To achieve a size slightly larger size than a conventional British twin, the Square Four utilizes two crankshafts running in parallel within a common crankcase. Displacement for the Mark I is 997cc, and the four cylinders share a common aluminum cylinder block and OHV head.
The engine was rebuilt during the seller’s ownership with components from Draganfly Motorcycles in the UK. New pistons, valves, guides, timing chain, and a Morgo oil pump were installed, and the connecting rods and camshaft were reconditioned at this time. Additional photos from the rebuild are provided in the gallery below.