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Stuck in the ’80s with the Slickest Yamaha 750s | Motorcycle Tales

Motorcycle Tales – Yamaha 750s

The May 1981 issue of Cycle World magazine told of the coming of Yamaha’s first V-twin cruiser, the XV750 Virago, and the June issue followed up with a piece on Yamaha’s Buck Rogers bike of the future – the XJ750RH Seca. Cycle magazine featured both in its June issue — as cover models, no less.

They were touted as some of the most innovative 750 cc machines in the early 1980s. What was the excitement about and does it hold up all these years later? For that matter, do the bikes hold up? Let’s see – starting with the Virago.

The XV750 Virago was Japan’s first serious attack on the legendary Harley-Davidson Sportster. The Virago came with an air-cooled V-twin, low, scooped saddle, smallish tear-drop gas tank and buckhorn bars; things that gave the Sporty its studly appeal. But the Virago was a decidedly different animal in several ways.

The absence of rear shock absorbers is a difference that gives the Virago a hard-tail look. The Virago was the first cruiser to bring monoshock rear suspension—generally limited to motocross and road racing bikes at the time—to the street. Air adjustable rebound damping and dial-up spring rate adjustment make tuning the rear suspension easy and the forks are air-adjustable, as well.

The look of the Yamaha’s SOHC engine presents another difference from the 45-degree included angle of the pushrod Harley. Yamaha opted to spread the cylinders apart 75 degrees, which enables better primary engine balancing and created the room to jam two Hitachi 40mm constant velocity carburetors down between the cylinders.

The twin carburetor set-up gave the Virago about 60 horsepower at 7000 RPM and 46 ft/lbs of torque at 6000 RPM, roughly a 10 horsepower advantage over the single-carb 997 cc Sportster of the day.

Another difference was caused by the use of the engine as a stressed member of chassis along with the pressed steel backbone frame, eliminating the down tube and cradle elements in the Harley design.

The Virago engine is a “contra-rotating” design, with the crankshaft turning in the opposite direction from the wheels. This was done to allow power delivery directly from the crankshaft to the transmission via straight-cut gears with no jackshaft in between.

In turn, the five-speed transmission could then be drawn up almost directly under the engine, making for an amazingly compact engine and transmission package. Add shaft drive and you have a major departure from the status quo in the V-twin cruiser class of the day.

Fresh as it was, not all was rosy in the Virago design—starters on early models were clunky and failure-prone, the single-piston front disc brake had marginal power and changing the cartridge-style oil filter was a pain. The odd name was something of a drawback, too.

While the Virago shook up the design of the V-twin cruiser, the XJ750RH Seca brought some new ideas to the sport/conventional bike class.

The Seca is credited for pioneering the street application of anti-dive front suspension. Road racing machines had first been equipped with anti-dive systems in the late seventies, but it had not yet reached street bikes.

In contrast to the “better plan ahead” front brake on the Virago, the Seca double disc brakes were all business. They look typical except for the hydraulic lines dropping down from the caliper to the bottom of the fork legs.

Under hard braking, as system pressure rises, a poppet valve opens to transfer some of the pressure to the bottom end of the fork legs, limiting the compression of the fork, keeping the bike level and the rear wheel on the pavement.

Atop the air-adjustable forks, there is an over-under light system with a huge, rectangular halogen torch mounted above a smaller high intensity fog lamp. Astern the dual lights is a space shuttle style instrument panel.

There are LCD indicators for brake fluid level, head and taillight burnout, oil pressure, battery electrolyte, and an indicator that warns when the side stand is down. A pre-ride system check runs automatically at start-up and on demand. An analog tachometer and speedo round out the instrument pod. The electronic fuel gauge reads out in a four bar LCD, like cell phones do today.

When the sensors detect a problem, a large red warning light flashes and the appropriate LCD indicator tells the rider what the problem is. Like the Virago, the Seca has self-canceling turn signals and a kill switch mounted in the side stand pivot, which shuts the engine off if the bike is put in gear with the stand down.

The Virago fit its niche performance-wise getting 13.44 second quarter mile runs at 98.6 mph according to period tests. Not fast, but respectable for a cruiser. The Seca, on the other hand, got noticed for being quick, turning the quarter mile in 12.52 seconds at 106.25 MPH, the second lowest E.T. in a four bike test done by Cycle World magazine in September, 1981. In that same test, it tied Kawasaki’s KZ750 for highest top speed at 122 mph.

The Seca’s air-cooled in-line DOHC four cylinder engine features the YICS (Yamaha Induction Control System), which creates fuel charge swirl to improve fuel economy. The system works, with the Seca wringing 55 miles out of gallon of gas. The Seca puts the power on the ground through a five speed transmission and enclosed shaft final drive.

Overall these bikes have stood the test of time quite well.

The Virago (an ’82) had its starter replaced at about 12,000 miles, one of the two vacuum operated fuel petcocks had to be rebuilt, and the ignition switch and voltage regulator have been replaced.

The Seca (an ’81) has over 34,300 miles on it. The stock mufflers rusted out about ten years ago and a Vance & Hines four-into-one pipe with re-jet replaced them. For comfort’s sake, the nearly flat, padded original handlebars were replaced with slightly wider chromed bars with about four inches of rise. It too, runs well and is still pretty quick.

In the years that followed, bikes from other manufacturers came out equipped with anti-dive, air-adjustable front suspension, mono-shock rear suspension, shaft drive, electronic gizmos in the cockpit and more radical styling. Even if the Seca and Virago didn’t inspire all of them, their innovations still work today and it’s not so bad to be stuck in the ’80s.

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