Once upon a time, the American motorcycle market was crowded with machines known, somewhat derisively, as "UJM's", for "Universal Japanese Motorcycle". Each of the Big Four offered them: A backbone-framed machine, invariably powered by a DOHC air-cooled inline four, available in Small (<600), Medium (750), and Large (~1000) sizes and, protestations of brand-loyal partisans notwithstanding, they were all much of a muchness.
You'd buy one of these bikes, grab an aftermarket catalog, and kit it out for the flavor of riding you liked best. Profiling on a Saturday night? Get some high bars, chrome bits, and shiny engine guards. Touring? Add saddlebags, a Vetter fairing, and highway pegs, and you were good to go. Interested in going fast? Flat bars, a four-into-one pipe, and some trick shocks turned the UJM into a "cafe racer."
Kawasaki cheated a little bit with its "Retro UJM", the Zephyr 550; the four-into-one exhaust gives away the slightly sporty pretensions, and the rest of the spec sheet would have been a box-stock racer's dream back in the day. The previous owner of my bike had made a few more modifications to enhance the bike's performance, and the end result is a fun and uncomplicated little bike to ride.
Even with the slightly wider-than-factory bars, the "sit up and beg" riding posture would be familiar to any UJM rider, although the deliberately lowered seat hight can cause the legs of taller riders to feel a little cramped. When parking, your toe won't find the sidestand where you think it would be; it's tucked up underneath next to the exhaust collector in order to gain a bit more ground clearance. This search for lean angle also means that a standard feature of the old UJM's, the centerstand, is nowhere to be found on the littlest Zephyr. The front brakes are surprisingly capable, with twin piston calipers more than powerful enough for a sub-450lb tiddler.
You'll notice I keep mentioning the longer-than-factory bars; years of sportbikes with low-mounted clip ons had gotten me into a bad habit of straight-arming the handlebars. The Zephyr cured this in about three miles of twisty pavement. With this much leverage on the front wheel, a bent elbow and a relaxed grip on the bars are called for, lest small unintentional inputs have the bike hunting for a line through a turn like a beagle puppy on a slack leash. Also, with the Yosh pipe and jetting to match, the ZR550 pulls a lot more like my RF600 than my old GPz. Crack open the throttle at 6500 in third on the GPz, and it would pull strongly but unspectacularly forward. Do the same on the Zephyr, and the bike will emit an exuberant bark through the endcan, as the bars get light and the tach needle jumps to the right. The acceleration is probably a lot closer to the RF's on paper, too; the Zephyr may give up fifteen or so horses to the newer RF, but it's a good fifty or sixty pounds lighter in the bargain.
I wouldn't pick it as my first choice for a roadtrip, but I already have a bike for that chore. All in all, it's exactly what I was looking for: simple and uncomplicated; a bike that's unafraid to display the 'motor' part of 'motorcycle'; light and tossable and equally willing to toddle around town at low revs or get wild-eyed and playful if prodded. The fact that it's dirt cheap, reliable, and gets good gas mileage is just the icing on the cake.