The Motorbike Archives

In a way the 250 Yamaha isn't "new." Most of the pieces have been around for a couple of years—as the Yamaha 350 R5. Although the 250 costs about $75 less than the 350 R5, the DS7 is as physically identical to the R5 as any 250 machine can be to a 350. If someone switched the sidecover badges, only a sharp observer could spot the lie. Externally the 250 carries slightly narrower tires than the 350. The 250 uses a 3.00 x 18 up front and a 3.25 x 18 on the rear, while the 350 is shod with a 3.25/3.50 combination. The long tapered mufflers distinguish the 1972 DS7 from earlier 350s—but the new R5s share the reshaped mufflers with the DS7.

Of course the heads, barrels and pistons are not common to both models. The displacement of the DS7 is 247ccs; bore and stroke dimensions are 54mm x 54mm. (The 350 has the same 54mm stroke, but the bore measures 64mm.) The 250, like the 350, has a five-port barrel: one induction, one exhaust and three transfer ports. The DS7 mounts two 28mm Mikuni carburetors, the same size instruments found on the R5. The lower engine cases house identical components with one exception the 250 pulls shorter (higher numerically) primary gearing. This change steps up the overall ratio in each gear, and that's expected: the 350 packs six more horsepower than the DS7, and the bigger engine can handle more gear.

Dogging the 250 DS7 doesn't make it, and the owner's manual clues the rider in: "Never lug your engine! (i.e., operate below 3500 rpm)" Should you insist on chugging the little Yamaha below 3500 rpm, the machine may well pay you back by eating sparkplugs. During break-in, the bike may suffer some fouling since the engine rpms should be held down. For the record, our machine fouled a set of NGK B-8HS plugs in the first twenty miles of testing; we installed another set of NGK B-8HS plugs which lasted the duration of the test. The plugs, when checked several hundred miles later, show a healthy medium-tan color.

The DS7 isn't particularly pipey; the power doesn't come pouring out in one great lump. The engine just gets stronger and stronger as the tack needle arcs upward. Nevertheless, according to Yamaha's figures, only ten horses are on call at 3500 rpm, so that figure establishes the floor for useable power. Spinning along at 5500 rpm keeps the engine well inside its strongest range; you can crack the throttle open at 5500 rpm in fifth and the bike accelerates quickly enough for normal highway passing. If you don't want to waste any time or space, drop to fourth and wring the engine out to 8000 rpm where the tachometer red zone begins. This strategy produces about 73 mph. We'd like to see fourth placed up a bit closer to fifth, so that an 8000-rpm blast in fourth would return 80 mph. Closer staging would make fourth a better gear for high-speed highway passing. Shifts go through—up or down—with lockstep precision. No vagueness or sloppiness gets between you and the gearbox. The transmission permits the rider the freedom to extend and exploit the willing little engine.

Yamaha intended that fifth gear be used. It isn't one of those way-way-overdrives suitable for plunging down cliffs. Hills and headwinds won't leave the 250 engine gasping hard at 75 mph—and the rider rowing down a cog or two. The power is there. The DS7 would pull 7500 rpm in fifth with Cycle's biggest staffer, who, sitting bolt upright, is about as large and aerodynamic as a mainsail. With His Largeness tucked in, the tach needle hovered around 8000, while the speedometer swung back and forth between 80 and 90 mph in a state of indecision.

The Yamaha 250 lets you know that it's working. With the engine boiling at a constant 6500, the induction system emits a baleful honking. Running hard on back roads you never notice this honking, because you're watching the road, clamping the brakes, slicing through gears, twisting the engine, and enjoying all those sensations that you pick up from the machine and the road. But after fifty straight freeway miles at 6500 rpm, you're ready to bail off the next exit ramp—and go sniffing around for a winding backroad.

Although the DS7 under freeway circumstances can beat your eardrums limp, the little Yamaha won't shake your hands or rattle your feet. Some two-strokes produce high-frequency vibrations which can be about as pleasant as plugging yourself into the nearest wall socket. You tingle all over, and it definitely isn't love. The DS7 doesn't exhibit the wallplug syndrome; it doesn't scramble images in the rear view mirror, it doesn't vibra-massage your hands and feet. Clearly, if you wish to hold the handgrips with your fingertips, you get tickled. Gripped normally, everything feels smooth. During the first couple hundred miles, the Yamaha transmitted some vibes through the saddle and foot-pegs, but only under hard acceleration. After 300 miles, these vibrations vanished.

The saddle is firm—perhaps just a bit too firm. After about 50 miles, you find yourself a little saddle sore, especially if the road is a straightline bore and you have time to think about your soreness. The seating position and the seat-to-control relationships work out best for riders under 5'10". Although the handlebars were spot on for our largest staff member, the space relationships between the saddle and foot controls weren't right. For him, the footpegs fell too far rearward. Consequently, with the ball of his foot resting on the right peg and his foot cocked in downward slant, his toe dropped under the brake pedal. Applying the rear brake meant jockeying the shoe around the brake pedal, lifting the foot up, and then depressing the pedal. Scooting back midway on the seat eased the foot problem somewhat, but then the handlebars stretched out his arms and rounded off his shoulders. So he settled for parking his toe under the brake pedal. Comfort is where the foot fits—unless you're under 5'10"—in which case all parts of you will fit.

The front forks really soak up bumps and ripples in the road; the rider doesn't take a jolting through the arms and shoulders. Nor do the rear suspension units pitch you off the saddle. The spring rates and damping characteristics, front and back, proved just about perfect. The ride isn't harsh; yet the bike doesn't wallow or surge when the cranked over in a ripple-laden corner. The DS7 always feels tight, responsive and all of one piece. Going through a series of S-bends, the machine can be flicked from side to side with almost no effort or conscious thought; it follows your mind as fast as your body can. In fact, the Yamaha 250 allows you to be sloppy of mind and steering. If you begin to run wide in a corner, you angle the bike over more and tighten up your line. There's no worry about digging the centerstand into a corner: the centerprop just won't ground out. Yamaha has located the folding footpegs up high. So if you touch a peg down in a high-speed bend, be warned: you're just about over far enough; the reasonable limit of street tire adhesion is well within limping and hobbling distance.

The frame accounts for a good measure of the DS7's excellent handling. Twin down-tubes drop from the bottom of the steering neck, loop down under the engine and then continue up and back, meeting the two top frame tubes a bit forward of the upper shock absorber mounts. Just above the swing-arm bosses, frame tubes run forward and upward, joining the two top frame tubes which proceed up front and connect with the front downtubes just below the steering neck. From the top of the steering neck, a single tube goes down and back, hooking up with a crossbrace which joins the two top frame tubes. The frame has substantial gusseting in the steering head area. All this tubework and gusseting holds the steering head and swinging-arm mounts in strict, unchanging alignment. The DS7 street frame resembles the one found on the Yamaha TD-2 roadracer. It's no accident that the DS7's frame is a strong, rigid affair. Or that the street Yamaha is a first-class handler. ►