1966 Yamaha YM-1 305 - 4-Page Vintage Motorcycle Road Test Article

Description

1966 Yamaha YM-1 305 - 4-Page Vintage Motorcycle Road Test Article
Original, vintage magazine article
Page Size: Approx: 8" x 11" (21 cm x 28 cm)
Condition: Good
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 displace-
ment 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 305’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 excep-
tional, 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, taper-
ing 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...