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The original YZ250 of 1974 used an air-cooled 250cc two-stroke engine of 70 mm bore and a 64 mm stroke, which was improved semi-annually. The air-cooled motor was replaced in 1982 with a 249 cc liquid-cooled two-stroke reed-valved engine with a mechanical, rather than servo-driven, YPVS exhaust valve for a wider spread of power.
Yamaha YA-1. YA-1 built August 1954, produced January 1955. The first bike manufactured by Yamaha was actually a copy of the German DKW RT 125; it had an air-cooled, two-stroke, single cylinder 125 cc engine [1]
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In 2003 it received an aluminum subframe, which was replaced in the 2006 model with an all-aluminum frame. The YZ250F has been praised for combining the broad-power characteristics of a four-stroke engine with the light handling more common in smaller, 125 cc two-stroke motorcycles.
In addition, the cylinders received a so-called Yamaha Power Valve System (YPVS). The first model series (TZ 250 A) of the water-cooled twin with contactless thyristor magneto ignition had a power output of 51 HP, the last expansion stage [clarification needed], the TZ 250 A (3TC) from 1990, 76 HP.
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The TZR250 was still raced in the Yamaha Past Masters race series with the British racing club as of 2024. [4] Racing engines are currently claiming about 56 hp (42 kW) at 11,000 rpm. [citation needed] Racing fuel ratios typically 1:30. Standard exhausts are difficult to improve on in terms of power and torque, but they are very large and ...
Having been discontinued in 1991 in favor of the Yamaha XT350, this model was reintroduced in 2008, replacing the Yamaha XT225, due to increased popularity of the 250 cc class. [4] The XT250 is branded the SEROW 250 in Japan.