Saturday, January 2, 2010

The mighty V-Twins

The late 1930's were a golden era for Royal Enfield. In 1938 the model line boasted 18 different models. Among them were the mighty V-Twins. They started in 1930 with a 976cc engine and crept to 1140cc in 1937 as in the model depicted here. It was used to tow a stylish enclosed sidecar rig, but was also available as a solo. The massive side-valve, twin-cylinder engine with totally enclosed valve gear had Royal Enfield's pioneering dry-sump lubrication system. It was probably the largest displacement motorcycle of its time. This large powerplant combined with a heavyweight, four-speed, hand-controlled gearbox to ensure that the Model K with standard ratios was ideal for both sidecar and solo use. Lucas 6 volt Magdyno lighting was standard as was black enamel finish with gold lining. The top-of-the-range Model KX featured detachable and interchangeable wheels and was marketed in solo form at 77 Pounds 10s 'or by gradual payments'. To give some perspective, according to this calculator adjusting for inflation that would be about 3700 Pounds today, but adjusting for average incomes it was equivalent to 15,000 pounds today, quite a pricey proposition! In a recent auction a solo model went for 10,000 pounds. In solo form the KX boasted 80mph performance and 65mpg economy at touring speeds. It made this top 100 motorcycles list, together with the Connie, the Crusader, the Bullet, the Flying Flea and the RE 200. The sidecar had comfortable seating for two, allowing four people to be transported. In spite of the massive engine, power was limited. The 976cc engine put out 22bhp at 3000 rpm. That is the same as a single cylinder modern Bullet 500! To tow those battleship sidecars would have been quite a chore, possibly facilitated by the more leisurely pace of traffic at the time. After the war these machines were probably too expensive for the prevailing economic conditions and eventually too expensive compared to cars. Royal Enfield concentrated on more nimble single cylinders and parallel twins after the war and did not produce any more v-twins after 1939. Any other ideas out there as to why no more v-twins after the war?


  1. Interesting post. I have read (can't recall where, sorry) that big thirsty twins were out of fashion due to economic hard times, the exception being the Triumph vertical twin because "it looked like a single"! In other words, it was no time for showy extravagance, even if you could afford it.

  2. Thanks, David. Tony Wilson-Jones also makes the following cryptic comment in "Enfield Engineer" about the sidevalve V-Twin engine: "These engines had followed the o.h.v. models in having fully enclosed valve gear, but while this feature proved an unqualified success in o.h.v. engines it added to the distortion problems always present with air cooled s.v. engines. So much was this that already before the 1939-45 war I, personally, had come to the conclusion that the s.v. engine was doomed as far as motorcycles were concerned"

  3. What is the con-rod crank pin layout on a KX ?



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