pistons arc moderately domed, producing a 9.3:1 c.r., and use internally-tapered wrist pins located in the center of the pistons, with no offset. Bore is 73mm, stroke 59imn for 494cc of displacement.    Primary drive is straight-cut gear to the clutch basket. From there, power is transmitted through the clutch hub to the transmission mainshaft, through one of the live gearsets to the driveshaft and through another set of bevel gears to the rear wheel The engine spins in the same direction as the wheels. Two 23mm Mikuni CV downdraft carbs are positioned between the cylinders. Along with the carbs there is a small, two-chamber tank that serves as part of the Y1CS (Yamaha Induction Control System). We've seen Y1CS before, on inline Fours, in which the intake ports of the engine are connected by small passageways intersecting each port just past the intake valve. An inline Four has regularly paced pulses in the intake tract and these passageways take advantage of the pulses to (in effect) boost the charge entering each cylinder in sequence.
   Another form of YICS appears on the Yamaha two-strokes, where the regular but more widely spaced intake pulses are stored and reinforced in a container now popularly known as a boost bottle.
For the Virago 500, Yamaha uses another form of YICS, this one shared with the 550 Vision. Because a V-Twin has an irregular firing order the Virago's secondary ports aren't connected. Instead each cylinder has its own chamber in a YICS tank, connected by a passageway leading to the intake port just above the intake valve. When the valve shuts, the mixture still entering tile port escapes up the passageway into the YICS chamber, which is precisely sized so pressure continues to build up until the intake valve opens again. When the valve opens, the pressure in the YICS chamber rushes into the cylinder again in the form of a jet stream and swirls the mixture entering through the intake port proper.
The rest of the engine package is simple enough: electronic ignition, wet sump, exhaust system with an expansion box (located just behind and below the engine), dual mufflers.
The engine is a stressed member of the frame, and there are no down tubes or engine cradle tubes. The four forward cylinder studs extend above the cylinder head and attach to a plate suspended from the frame's backbone. That backbone is formed of stamped steel plates, welded together in box section and curving from steering stem to swing arm pivot. The rear of the engine bolts to the backbone in two places, one above and one below the swing arm pivot.
The backbone is sealed and serves as (he air intake system, A rubber plenum, located under the seat and left sidecover,

feeds air into the backbone, which forms a still air box. A pleated paper air cleaner fits into the backbone just above the carburetors.
A single rear shock bolts to the backbone, under the front of the seat, and runs down and back to a triangulated steel swing arm. The frame rear subsection, which supports the seat and tail section, bolts to the backbone tube on the lop and the footpeg carriers on the bottom, The swing arm pivots in tapered roller bearings,
The leading-axle non-adjustable forks have 36mm stanchion tubes held by a steel lower triple clamp and an aluminum upper clamp. These clamps are different in more than material. The lower triple clamp has less offset than the top triple clamp, so the steering head angle is different from the fork rake. The difference is 1.5°, the steering head set at 39°, the forks set al 27.5°, producing a long 4.9 in. of trail. Two rubber-mounted risers boll to the top triple clamp and hold the tubular steel pullback handlebars. The front wheel is 1.85 in, wide and holds a 3.00-19 Bridgestone L303 tire, the rear rim is 2.5 in. wide and holds a 130/90-16 Bridgestone G509 lire. Both wheels are cast aluminum in the now common swirl pattern used on most Yamaha Virago and Maxim models. An I 1.75 in. disc is used for the front brake and a 7.1 in, drum is used in back.
Because the lowest part of the teardrop-shaped gas tank is lower than the carburetor float bowls, an electric fuel pump is used to feed the carbs. The pump supplies more fuel than the carburetors need, the surplus recirculating to the gas tank. According to Yamaha engineers, this recirculation system lowers gasoline temperatures an average of 50°, Lowering fuel temperatures can reduce evaporative emissions, which will be controlled on California motorcycles in 1984.
Instruments include a I 20-mph speedometer and a 10,000 rpm electric tach (redline is 8500 rpm), with a simple row of warning lights positioned below the instrument faces. Those lights indicate turn signal and high-beam use, low oil level and neutral selection. There isn't a fuel gauge; the gas tank petcock has a reserve position.
Comes now a persuasive case for simplicity, Because the two are very different motorcycles from the same factory, the Virago 500 and Vision 550 can be considered as two ends of same scale. Yamaha claims a modest 33 bhp for the Virago, an impressive 68 bhp for the Vision. However, the Virago's claimed torque is 30.4 lb, ft. at 7000 rpm against the Vision's 34 lb.- ft. at 8000 rpm, and with tanks half full the Virago weighs 402 lb. and the Vision weighs 482 lb.
Power requires weight, tuning means
 

the power grows out of rpm, and torque is mostly a function of displacement.
And at the drag strip the Virago turned 13.70 sec. for the quarter mile with a trap speed or 93.55 mph and the Vision (Cycle World, April 1983) did 13.05 sec. at 99.33 mph. More lo the point in daily living, in lop gear acceleration the Virago is actually quicker; 40-60 mph in 5.4 sec. vs 5.8 for the Vision.
Sure, the sporting Vision is quicker and faster and the more complex package can justify itself... to the rider who wants it.
(It's also interesting to note how close are the middleweight and big Twins, from Yamaha, Honda, Harley, BMW, Triumph, el al. Be they 1000, 750, or 500cc, they all turn the quarter mile in the high 12s lo high 13s while the big Fours are much quicker than their smaller brothers.)
Al any rate, the Virago's strong mid-range and easy-on torque supply make it great fun to ride on the street. It's perfectly happy tooling down the road at less than 3000 rpm, and will leave traffic behind when short-shifted at 4000 rpm. It's equally happy when run lo the red-line in every gear, the power delivery strong and steady with an extra kick of blip above 6000 rpm. The 500 is more willing lo rev quickly than the larger Viragos and stays smoother in the process. The 500 responds whenever the throttle is opened, no matter where the engine is in the rpm range. There isn't any surge at steady throttle when threading through traffic jams, and there's no hesitation off idle when the throttle is opened quickly. And all the time there's that intriguing V-Twin exhaust note, muffled on the 500 but there just the same, the off-cadence