- Pre-unit construction
Pre-unit construction, also called separate construction, is a
motorcycle engine architecture where the engine andgearbox are separate casings, with their own oil reservoirs, and usually attached to parallel plates that also attach to the frame. Even though Singer [ [http://www.ianchadwick.com/motorcycles/britbikes/brit_s.html IanChadwick "Brit Bikes S"] (Retrieved 25 November 2006)] offered an integrated engine and gearbox in a single casing in 1911, it was not until the 1950s that technical advances meant it was possible to reliably construct engines with integral gearboxes in one "unit", known asunit construction . Another variant is "semi unit construction", where the gearbox is bolted directly to the engine.The term pre-unit is particularly applied to BSA and Triumph vertical twin motorcycles as a consequence of the strong publicity attached to their change to the unit construction of vertical twins in the early 1960s. Norton and
Royal Enfield kept producing separate construction engine and gearbox motorcycles.The 1969 "Isolastic" frame
Norton Commando had the engine, gearbox, "and swingarm" bolted together on plates bolted to the frame with shimmed rubber bushes.Among the Japanese manufacturers, Kawasaki produced a separate construction 650 cc vertical twin, inherited as a consequence of taking over Meguro in 1964,cite book|title=The Illustrated Encyclopedia of Motorcycles|author=Erwin Tragatsch (Editor)|Publisher=New Burlington Books|date=1979|edition=Edition: 1988|page=207|ISBN=0-906286-07-7] . The Meguro 650 was a copy of the BSA A7 and A10 design, external appearance was similar although no parts are interchangeable. [cite web|url=http://www.ianchadwick.com/motorcycles/w650/history.html|publisher=Ianchadwick.com|title=W650 History|accessdate=2007-01-14]
References
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