The faithful old XS650 has been around since 1968, and when launched was the largest road bike Yamaha made, and I think it was their first foray into 4 strokes of any real size.
The bike's a vertical parallel twin, 2-valve per cylinder, overhead cam, and has been called the Japanese Bonnie. The first models were was kick start only, the electric foot being added around 1972.
The engine and gearbox are integral ('unit construction' for those into the Brit stuff), so the wet sump engine's oil has to deal with the gearbox 'shearing' effect along with the normal 'engine wear' component, with only a couple of gauzes to protect things (as per, say, Triumphs of the era - Pre-unit stuff like older British and HDs were built with a separate engine and gearbox, and therefore ran separate oils).
Up until around about 1978, all models were the 'roadsters' (spoked wheels and traditional styling) then the 'US Custom' hit the scene, with cast wheels, stepped seat, high-rise bars and fatter rear tyre.
The XS650 was raced on the American Flat Tracks with fair success, and in the past decade or two (or three?) has become a popular bike with folks wishing to make customs/bobbers/choppers/rats/whatever.
Infact, your more likely to see a customised XS650 than a stock one (so which is the rarer?)
Over the years, various Monkeys have played with XS650s, so here's a chance to have a thread that shows your bike...
So details - Whats been done, what you call it (bobber etc), why ya did it, how good/bad is it, what's next, how long have you been into them and PICCIES
http://en.wikipedia.org/wiki/Yamaha_XS_650http://www.xs650.biz/p/28/1423/home Europe outlet for MikesXS
http://www.mikesxs.net/ MikesXS in the USA
http://www.xs650.com/http://xs650temp.proboards.com/index.cgi?board=Fuel&action=display&thread=7705http://www.cmsnl.com/yamaha-xs650-b-1974-1976_model8524/partslist/http://www.yambits.co.uk/http://glchoppers.webs.com/xs650buildspage1.htm