PAR­AL­LEL TWIN

Motorcycle Monthly - - Knowledge -

Lay­out: Two cylin­ders next to one an­other, con­nected to a com­mon crank­shaft. Ben­e­fits: Nar­row lay­out, strong torque, good econ­omy.

The par­al­lel twin was to form the back­bone of the Bri­tish mo­tor­cy­cle in­dus­try for the best part of 40 years. There are many sto­ries to its cre­ation, but a pop­u­lar his­tory is re­lated to Ariel’s chief en­gi­neer Val Page, who ex­per­i­mented with two cylin­ders from the firm’s square-four mo­tor.

He saw the po­ten­tial in the con­fig­u­ra­tion and, switch­ing jobs to work for Tri­umph, went on to pro­duce the ‘6/1’ 650cc twin in the early 1930s for use in pow­er­ing side­cars. Tri­umph’s Ed­ward Turner took up where Val left off and was ac­count­able for the Speed Twin in 1937, which proved such an im­pres­sive con­fig­u­ra­tion that ev­ery­one from BSA to Norton adopted the en­gine-type.

The Ja­panese also saw the po­ten­tial in the twin de­sign and fa­mously put it to the Bri­tish in the 60s with Honda re­leas­ing the 450cc twin Black Bomber in ’64, while Yamaha over­whelmed the twin mar­ket in 1968 when it re­leased the XS650. Nowa­days, twins are favoured for their mild na­ture and good econ­omy.

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