Cycle News - Archive Issues - 1980's

I ~ Yamaha ~ & Sr£a ~ E Want a -Yamaha 750? . - For 1981 Yamaha has Ioeded both berrels of their 750 shotgun. Pull one trigger and you get e V-twin. Pull the other end you get en in-line four cylinder. Which _ trigger you puR you get sheft drive. Although both the Sec:a end Virago e,. iclenticlll in weight, there's e world of difference that's much Jerger then JU8t the cylnder configurations would lead one to believe. Let's look at the V·twln first end then go on to the Seca. Virago OK, let's get one thing out of the way right now. The 748cc !? h Yamaha VIrago as nothing to do with Harley-Davidsons or Ducatis or Moto Morinis, and anybody who believes that it does probably thinks that parts from a 327 Chevy are interchangeable with a Ford 302. since they're both V-8s. No, the Virago is not an oriental Harley, and Lord knows that people who would buy a Harley would never buy a Yamaha, and vice versa, no more than people who would buy a Yamaha XS650 would buy a Triumph 750. The Virago, like most Yamahas these days, is the product of something called market research, the same stuff that spawned the Xj650 Maxim and the 250cc Exciter I, both being hiwater marks in the naming of motorized vehicles. What Yamaha did was sit down a bunch of people and let them in effect design their dream motorcycle by using clear plastic overlays -Vith outlines of motorcycle parts enscribed on them. A guy could take this frame and put on this seat and that tank and iosen his favorite engine. Yamaha found out that most people liked real low seats and semi-chopper styling and in-line four-cylinder engines with shaft drive. so they built the Maxim and it sold like hotcakes. But along with the overwhelming desire for that bike they also detected a ground swell of suppon for cafe styling, a limited but significant potential market, and so built the Seca 550 and Seca 750. That done, Yamaha could deal with one of the big surprises of the research, which showed that something like one founh of the people surveyed were interested in a V -twin engine but wouldn't buy any V-twin then on the market, Harleys being too expensive and too underpowered and too vibratory and too unreliable; Ducatis being too expensive and too hard to find parts for and having such poor electrics as to risk failure at any moment; Moto Morinis being too small and all of the above as well. So Yamaha took that information and the certain knowledge that Americans love shaft drive, fed it into the computer in japan and came up with the Vira~, an unusual name which appears In the Ribald Classic in the March issue of Pi4,boy, for God's sake. Virago is a name which isn't quite as simple as Maxim, which one infers has something to do with maximum, (always a word dear to the American hean), or Exciter, which must have something to do with excitement, perhaps sexual dear to excitement, also the...ah... well, let's skip it. Anyway, the dictionary defines Virago as meaning, among other things, "a loud, overbearing woman," and "a woman of great strength, stature, and courage." That may mean that the Virago is a nice bike, for a girl. Virago also sounds quite nicely like "Volare" as in the song sung in the Chrysler automobile commercial, and anywhere that fun-loving motorcycle enthusiasts gather a modification of that Volare theme song may ecbo off the walls. Vi-ra-go, o-o-ohh, Vi-ra-go, o-o-ohohh... We digress. Back to the machine at hand, the Yamaha Virago. Perhaps it is suitable to refer to the bike as being overbearing, as in the definition quoted above, because it does, after all, have overhead cams, carns being rotating shafts with bumps on them, rotating shafts needing bearings, which means that any overhead cam engine is also an overhead bearing engine, or overbearing for shon, in the terminology of the criminally insane. Back to business. Business in this case is, as mentioned, 748cc, 83mm bore and 69.2mm stroke. The compression ratio is S.7:1. There are two valves per cylinder, intake valves being 43mm in diameter and exhaust valves being 37mm. Valve lift for both intake and exhaust is 9.7mm. Intake valves opens 43° BTDC and close 6S0 ABDC; exhaust valves open SOO BBDC and close 32° AToe. Duration for intake and exhaust is 292°. The cylinders are arranged in a 75' V. a wider angle than HarleyDavidson's 45° and a narrower angle than Ducati's 90'. It's 75' because the Yamaha computer said that 75° was the best compromise allowing room for two 40mm carburetors located between the cylinders without making the engine too tall or too long or too shaky. Cylinder angle, it seems, has a big effect on engine vibration. 90" is smoother than 45°, and 75° is smoother than 45° without being as long as 90°. The crankshaft has ball main bearings and two-piece, plain-bearing connecting rods on a common crank pin, the rear rod and piston and cylinder and head being offset to the left, which incidently improves air flow (thus, cooling) to the rear

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