Royal Enfield 1931 Model J31 499 cc 1 cyl OHV 3605

Royal Enfield 1931 499 cc Model J31 De Luxe Two-Port OHV frame # 10620 engine # J4405

video: https://youtu.be/9I5bLaz39KE

“The late Twenties had proved a difficult period for the British Motor Cycle Industry, with periods of industrial unrest, which saw many manufacturers go to the wall. British motorcycle production had fallen from a peak figure of 160,000 in 1927 to 126,000 in 1930, would drop to 74,700 in 1931 and to as low as 52,200 in 1933 before the turning point of the Great Depression. The Enfield Cycle Company had weathered the initial downturn in the market better than many other manufacturers. During the post-war period the works had been expanded year on year to meet demand for the company’s products and was among the most modern and best-equipped in the country. The company had always offered well-engineered designs and by using the latest production methods the machines could be sold at competitive prices. The company was in a better position than most at the start of the Thirties.” (source: Peter Miller, Royal Enfield, The Early History 1851 to 1930)
Sloping engines were first introduced by RE for the 1930 model year, after the style popularized by the successful BSA Sloper models. Dry sump lubrication was also introduced that year on two De Luxe models. The oil was carried in an extension of the crankcase and was pumped by a feed pump through the crank pin and flywheel to the big end and from there distributed by splash to the rest of the engine. It was then collected in a shallow sump and pumped back to the forward chamber by a return pump. The advantage of this system was the absence of a separate oil tank with external oil pipes, that gave these models a very uncluttered outer appearance.
The Model J and its economy version JA were introduced in 1930 as 488 cc overhead valve machines with bore x stroke dimensions of 85.5 x 85 mm. The “De Luxe Two-Port OHV” J, with a price of £55, was the most expensive single in the model range; this price didn’t include electric lighting. The 1931 model range still comprised the 488cc Standard JA, but a revised model with duplex cradle frame and 499 cc long stroke 80 x 99.25 power source became available as Model J.
The J we present here has been restored to a high standard in the 1980s and is an excellent runner. She was sparsely ridden till the mid-nineties, since when she’s been stored indoors on room temperature and has been regularly cared for. She comes with Bosch electrics – even in Britain considered superior to the Lucas products- and there’s passenger accommodation in the form of an elaborately sprung seat. The Terry saddle has a quality leather finish and the oil sump is protected by a metal sheet. The hand-change 3-speed gearbox is a Sturmey-Archer product and parking is made easy by the practical side stand, not often available on early thirties machines. Noteworthy is that the ignition advance is not effected by a lever on the handlebars, but by turning the left handlebar grip. The absence of external oil lines gives this well-designed, quality post vintage single a clean and purposeful look, which is enhanced by the thoughtful way the control cables have been led through the handlebars.