Yamaha 80 Yg-1
YAMAHA 80 YG-1
Road Impression;
CYCLE WORLD has often had the privilege of spending time with Yamaha motorcycles. In each case our findings and opinions met with comments inclined towards a suspicion that we had sold out our integrity to Yamaha. So staunch was our enthusiasm for the Japanese two-strokes, some of our critics felt we could not possibly have liked them so much. This is of course nonsense; there are many machines in the cycle world we like a great deal, and the Yamaha 80 YG-1 is another one, a fact that pleases us considerably.
Without hesitation we will be happy to tell anyone who might care to listen that this machine is just about the smoothest thing on two wheels; it performs like a number of good 125's, is one of the best finished and assembled bikes around, bar none, and with no regard to cost or size, and is pure delight to ride. Most of this is a little difficult to understand, since the almost singular claim to distinction is the method of induction of the fuel/oil mixture into the engine, via a rotary disc inlet valve.
Yamaha's success with the 80 is probably due to this feature, usually found only on racing machines. In simple terms, the rotary induction system controls the intake of fuel into the engine through a piston controlled port, but the rotary system involves the use of a disc with a hole in it that rotates with the crank. The carburetor is mounted opposite an opening in the crankcase that is exposed when a corresponding window in the disc is in alignment. What it means is that the engine has time to inhale more mixture over a longer period of the cycle. Just as importantly, it allows the engine to retain the mixture right up to combustion; in the piston controlled engine the mixture can escape out the exhaust ports if the duration between intake and exhaust is delayed too long. This delay, called "overlap," simply allows the engine to retain a larger fuel charge right up to combustion,a larger fuel charge of course means a stronger detonation and more power and much smoother running. In theory this means more horsepower; just as important, though, is its smoothness at low engine revolutions, giving it excellent power without having to "buzz" at high rpm to utilize the minimum of power usually associated with small displacement engines. In short, the rotary valve makes the engine quite powerful for its size, with a wide splay of pulling power, and extremely smooth.
Yamaha also has a trail version of the YG-1, called the Trailmaster, to be the subject of a CYCLE WORLD Trail Test at a later date, that well utilizes the excellent advantages of this induction system. Power at a minimal loss of traction due to wheelspin is a distinct facet in a trail machine; our off-the-road experiences should be very revealing.
Few machines can stand the close scrutiny the YG-1 invites; it is appealing as only a well-executed mechanical device can be. Paint, chrome, metal finishing and what little plastic is employed is first rate. Little delightful details abound; rubber scuff pads on the front fender to prevent the control cables from marking up the fender; a well-designed and executed air cleaner looking more like a vacuum bottle; a total absence of a visible carburetor, which turns out to be buried under a metal cover on the right side of the engine; neat little turn-indicator lights that are round, as lights should be, and very bright; two-tone blue and silver paint of apparent top-quality; a full chain cover that leaks not a drop and silences the whole operation; a handsome nacelle that houses the headlight and easily read speedometer; etc.
Most Japanese machines with which we have had experience used an over-abundance of thin plastic parts, such as fenders, battery and tool box covers, fork covers, etc. Yamaha's has a grand total of one (count 'em) plastic parts; the small covers on the rear shock absorbers. Truth of the matter is, we found little to criticize, assuming, of course, the reader is either a newcomer to motorcycles or simply prefers small machines. Though not a wild, exciting charger, the YG-1 is fun to ride, and a bargain as well.
Technical specifications are as follows; Engine; single cylinder, two-cycle; 47mm x 42mm bore/stroke, actual displacement 73 cc, 6.8:1 compression ratio, 6.6 hp @ 7,000 rpm, battery ignition system; gear primary drive to four-speed gearbox through wet multiple disc clutch; 45.1 inch wheel base, 37.8 inch height; dry weight 140 pounds; 176 miles per gallon claimed mileage; maximum speed claimed, 53 mph. We can add that our attempts at top speed runs were hampered by the newness of the engine but its claimed performance can probably be exceeded.
Unanimous conclusion of every member of the CYCLE WORLD staff; a very very nice little machine.
