Yamaha Ym-I 305
YAMAHA YM-I 305
One-third Liter Roadburner
YAMAHA started out in the music business in 1887, which will explain the crest used on their motorcycles — three tuning forks. Although the company has spread to the international two-wheel trade, happily we can report that they are still making music with their 305cc road machine.
They call the YM-1 the “Cross Country Sport 305.” This has nothing to do with bouncing over the boondocks; rather, Yamaha means this bike to be the roadburner of the line. They succeed admirably, producing a medium displacement motorcycle for town and touring with the power and feel of a much bigger machine.
The YM-1 engine is a “big cousin” of Yamaha’s 246cc YDS-3, the two showing similarity in design and running charactertistics. The YM-1 has bore and stroke dimensions of 60 x 54mm, compared to the YDS-3’s 56 x 50mm. But “big cousin” is more mild-mannered; the torque value is up about 20 percent while the displacement has increased 24 percent. This is explained by the compression ratio — 7.1:1 — instead of the 7.5:1 of the YDS-3. Advantage of this is that the pistons have to suffer less thermal loading, contributing to better wear and reliability. One may have no fear in using regular grade gasoline, which will make up a bit for the 3 05’s largish appetite (which goes with a largish disposition, to be sure).
Yamaha now claims 29 bhp for the engine, which is curious, as it has not been changed significantly since it first came on the market with claims of 26 bhp. The change is most likely one of literary license to make up for the rather conservative smaller figure. The power peak is at 7,000 rpm and the engine pulls very strongly from about 5,000 through 8,000 rpm. This wide power band, coupled to the five-speed transmission contributes to an exceptional, yet flexible, performance. The higher torque of the 305 allows it to pull higher first and second gears than on the YDS-3. Fourth and fifth gears are closer on the YM-1, the fifth speed having “overdrive” characteristics and not being much good for acceleration until 65 mph is reached.
The 305 is the latest of the Yamaha line to have the proven “Autolube” oil injection system, which removes two bugaboos for potential two-stroke buyers — the hassles of mixing oil with gasoline at each fuel stop and the blue smoke issuing forth when the engine is running at less than full tilt. The rider must only check the oil tank window from time to time to ascertain that the level is up. The oil is mixed with the gasoline in variable fashion, the gas/oil ratio being 20/1 at full throttle, tapering off to 200/1 at idle. The virtues of this system are its relative oil economy, combined with a reduction of carbon and varnish residues.
The 305 is an easy starting machine, even without electric starter. The novice rider need not worry about involved or ritualistic starting procedures, but has only to turn the key, flick the choke lever and kick the starter, once or twice at the most. It is necessary to let the engine warm a few minutes or it won’t go anywhere. Blip the throttle a few times to see that it’s warm »enough to take a torque load and then pop it in gear.
We noticed that the tachometer doesn’t operate when the machine is in gear and clutch disengaged, but works in neutral with the clutch out or, naturally, when one is under way. This is because the tach is driven off the transmission mainshaft, which becomes motionless when the clutch is disengaged. It would be worth noting that the oil pump has the same source of power, so don’t do any way-out throttle blipping over extended periods of time with the clutch lever squeezed in.
CYCLE WORLD ROAD TEST
Gear shift action is very smooth, except for the change between first and second (which passes through neutral). This must be made with a deliberate kick. The virtues of the 305 don’t begin to show their subtler shades until it’s rolling about 65 to 70 mph, at which speed the engine is buzzing smoothly as an electric motor. There is virtually no engine vibration until 7,000 rpm is reached. At legal road speeds, the revs are less than 6,000 rpm.
The brakes are smooth and progressive, offering exact knowledge of how much brake one is really reaching for. This is particularly important, as the front brake may be locked on dry pavement. The 343-pound curb weight of the machine, along with its low center of gravity and steering geometry, gives an extremely stable feel at high speeds over winding roads. Suspension has that moderately stiff feel without being too much for long distances. Should one be going at a goodly pace with the machine cranked over, there is no noticeable wobble, frame flex or tire skip when one hits striations, tar spots and ripples. A few of our testers managed to bottom some of the underside though. Damping is provided by the traditional friction device, adjustable by the large knob on the steering head. It is suggested that one not be overzealous in tightening this, for it seems easy to go too far; this results in a bizarre feeling when speeds drop to where such damping is unneeded.
Seating position, and the handlebars provided with the machine, make for comfort over extended periods of cruising. The two-in-one tachometer and speedo head is very easy to read. Tach dial is a different size than the speedo dial, so there is little chance of confusing the two. Large lights indicate neutral gear position and generator charging.
A very attractive and high quality finish tops off what is, in sum, a fast and easily ridden road cruiser for novice or veteran. ■
YAMAHA YM-1 305
$ 699.00
