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The Yamaha XS650 is a mid-size motorcycle made by Yamaha Motor Company. The standard model was introduced in 1968 and produced through 1979. The "Special" cruiser model was introduced in 1978 and produced through 1985. The XS650 began with the 1955 Hosk SOHC 500 twin. After about 10 years of producing 500 twin, Hosk engineers designed a 650 cc twin. Later the Hosk company was acquired by Showa Corporation, and in 1960 Yamaha had bought Showa with Hosk's early design of 650 cc twin.〔(【引用サイトリンク】 Yamaha XS 650 )〕 When the Yamaha XS 650 was launched in 1968 it had one of the most advanced engines in its class of large parallel twin motorcycles. The engine and gearbox are unit construction with the crankcase split horizontally for ease of assembly whereas almost all contemporaries in its class in 1968 are either unit construction with a vertically split crankcase or pre-unit construction with separate engine and gearbox. The XS650's engine was used in AMA Professional Dirt Track Racing by national champion Kenny Roberts. In 1968 only the Laverda 750S, also launched that year, matched the XS 650's modernity of unit construction and SOHC valve operation. ==Model history== The 1970 model was designated the XS-1. Subsequent Yamaha Xs650 models〔(Yamaha Xs650 model ) ID table, Code, Serial Number, Year, Color(s) - Xs650chopper - Retrieved 2013-07-24〕 were XS-1B (1971), XS-2 (1972), then TX (1973), TX-A (1974), XS-B (1975), XS-C (1976), XS-D (1977), XS-E (1978), XS-F (1979). 1979 was the last year of the so-called "Standards" (an unofficial term commonly used to differentate it from the "Special," which has pullback bars, a teardrop tank, and other differences in appearance). The Es and Fs also came in Special form: XS-SE (S for Special) and XS-SF. From then on they were Specials only to XS-SG, XS-SH, XS-SJ, XS-SK. There was a Special II (Two) model designation in 1979 (XS-SF-II), 1980 (XS-G), 1981 (XS-H) which were models with fewer chrome parts and drum rear brake (1979, 1980) or wire wheels (1981) versus disc rear brake or cast wheels. The first two model years (XS-1 and XS-1B) were kick start only, with an electric starter added from the 1972 model year on. This had a compression release added to the front left exhaust tappet cover resulting in a square versus triangular cover found on the other exhaust and intake covers. Upon removal of the compression release mechanism in 1974 due to uprated starter, the square cover at the left exhaust valve was continued. Brake modification notes: * Drum fronts on early models cannot be changed. * Pre '77 & post '77 fronts have different (offset) brake discs, the wheels swap but not the discs. * Drum rear wheel into rear disc frame needs the rear drum frame swingarm too. * Disk rear wheel into rear drum frame needs the rear disc frame swingarm and also needs brake master-cylinder lugs welded to the frame. Handling differences on swapping rear wheels:- * Standard rear tire is 110/90-18. Special rear tire is 130/90-16. Because the Standard tire is narrower it will tend to steer a bit more quickly. Because the Special tire is wider it will tend to be a bit steadier in a straight line. Overall gearing is not changed from the Standard, as the two tires are essentially the same outside diameter. Prior to the XS-B model, the bike had a reputation for speed wobbles but adjustments to the 1975 setup overcame these. 1976 models had the front brake caliper moved to the right fork leg, behind the fork as opposed to in front of the fork. This placed the brake caliper nearer the steering pivot center-line, requiring slightly less effort to steer. Mid-'77 the front forks had a major redesign, fork tube diameter increased from 34 to and internals were changed (although this also holds true for various years of the same tube size). The entire fork assembly (with triple tree) will swap either way but fork parts are not equivalent. Also the brake caliper changed from a dual piston cast iron design for the fork to a aluminum single piston floating caliper for the forks. The brake caliper mounting lugs on the fork sliders are of different spacing for the and forks so the calipers can't be swapped. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Yamaha XS 650」の詳細全文を読む スポンサード リンク
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