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GRI were motorcycles produced from 1920 to 1922. Distributed by Macrae and Dick of Inverness, the engine was designed by G. R. Inshaw.
The machine was first promoted in 1920 and was produced in 348cc and 496cc sizes with one overhead valve opened by a chain-driven ohc and rocker, and a rotary valve.
The engine was fitted into a conventional frame with Brampton forks. It had a two-speed Sturmey-Archer gearbox with belt final-drive.
As rotary valves were noted for being unreliable, the public did not take to the machine and it soon slipped from sight.
George Richard Inshaw (1888-1951)
"GEORGE RICHARD INSHAW was born in Birmingham in 1888 and received his theoretical training in engineering at Aston Technical College. In 1910, on the conclusion of a four-year apprenticeship with Mr. John G. Inshaw, Birmingham, engineer, he continued in the latter's firm as a draughtsman for a further period and subsequently held the position of consulting engineer and designer to the Inshaw Rotary Engine Syndicate, Ltd. His capacity for design gained him several patents which included the Inshaw Rotary Engine, designed and constructed at the works of the Gnome and Le Rhone Company, Ltd., Walthamstow; the G.R.I. motor-cycle single poppet-valve engine; and (jointly) the Inshaw Patent Steel Tube manufacturing plant, which was subsequently installed at Stewarts and Lloyds's works. For some years Mr. Inshaw was designer and consulting engineer to G.R.I. Motors, Ltd., Glasgow. Subsequently he went into business in the same city and became the managing director of the Unicone Company, Ltd., makers of a patent pipe joint which was designed and patented by Mr. Inshaw. He continued to hold this position until his death which occurred on 27th August 1951. Mr. Inshaw had been an Associate Member of the Institution of Automobile Engineers since 1922."