Yamaha XS850: A Leaner Legend

The world of motorcycling is often a journey through time, where understanding the innovations of the past can illuminate the brilliance of the present. Yamaha, a brand synonymous with musical instruments and a rich automotive heritage, has a fascinating chapter in its history involving three-cylinder engines. While many riders today associate the triple configuration with the likes of Triumph and MV Agusta, Yamaha was an early pioneer in this distinct engine layout, particularly with its XS750 and the subject of our focus, the XS850. This article delves into the evolution of Yamaha's triples, exploring what made the XS850 a unique, albeit sometimes controversially lean, machine.

The Dawn of the Yamaha Triple: The XS750

To truly appreciate the XS850, we must first cast our minds back to 1976. The motorcycle landscape was dominated by the inline-four cylinder configurations of the Kawasaki Z1 and Honda CB750. In an effort to offer something novel and exciting, Yamaha introduced the XS750. This machine was distinctive not only for its three-cylinder engine but also for its remarkably smooth operation, a trait not typically associated with triples of that era. The engine itself was a testament to Yamaha's engineering prowess, featuring an iron block, a forged steel crank with two-piece connecting rods, and plain bearings. The dual overhead cams were reliably chain-driven, and the air-fuel mixture was managed by 34mm Mikuni carburetors.

Power was delivered to the rear wheel via a five-speed gearbox and a shaft drive. A key element contributing to the XS750's refined ride was Yamaha's innovative use of Constant Velocity (CV) U-joints at the swingarm pivot. Unlike the more common, and cost-effective, Hooke joints of the time, CV U-joints allowed the swingarm to articulate smoothly through its travel without transmitting driveline fluctuations. This meant a more consistent power delivery, even as the suspension worked. While never the outright horsepower leader against its four-cylinder contemporaries, the XS750 carved out a niche for itself through its exceptional ride quality and unique character. Its suspension was also noteworthy for 1976, with twin rear shocks offering five-position preload adjustment and telescopic forks with three-way adjustability. This combination contributed to a surprisingly compliant and well-mannered ride, effectively mitigating fork stiction, a common issue that plagued many bikes of the period.

The Quest for More Power: Enter the XS850

As the motorcycle industry matured, so did customer expectations. The desire for increased performance, particularly horsepower, became a driving force. In response to this demand, Yamaha unveiled the XS850 in 1979. While the name suggests a larger displacement, the XS850 actually measured 826cc, achieved through a 3.5mm increase in bore size over its predecessor. This wasn't merely a simple bore-out; Yamaha engineered an entirely new cylinder head and made numerous internal modifications to accommodate the larger pistons and increased stresses.

However, the early 1980s brought a new challenge: increasing environmental awareness and stricter regulations from bodies like the Environmental Protection Agency (EPA). To meet these nascent emission standards and ensure cleaner combustion, Yamaha opted for a different carburetion approach for the XS850. Instead of the familiar Mikuni units, the XS850 was fitted with Hitachi carburetors that were notoriously jetted incredibly lean. This, combined with a highly restrictive muffler and complex air intake plumbing, resulted in an engine that, while compliant with emission tests, suffered a significant performance deficit. The pursuit of environmental responsibility, unfortunately, translated to a noticeable dip in the bike's power output.

The Rider's Response and Modifications

It's a common narrative in motorcycling: when a bike is delivered with performance held back by regulations, riders will inevitably seek to unlock its true potential. The XS850 was no exception. Owners quickly discovered that by replacing the restrictive mufflers with free-flowing aftermarket units, re-routing the air intake for better flow, and crucially, re-jetting the Hitachi carburetors (or often swapping them for Mikunis altogether), the XS850's inherent power could be unleashed. These modifications effectively negated the lean-running condition and restored the performance that many felt was unnecessarily suppressed.

Beyond the engine, the XS850 continued to build on the XS750's strengths in suspension and handling. The introduction of air-assisted front forks offered riders the ability to fine-tune the front end's stiffness by adjusting air pressure, a feature that, while having its quirks, generally provided a good ride. Combined with the capable chassis and the continued use of smooth shaft drive, the XS850 proved to be an engaging machine for exploring twisty roads. Yamaha's attention to comfort was also evident, with rubber-mounted handlebars and engine mounts, along with a plush seat, significantly reducing vibrations and enhancing the overall riding experience. Contemporary reviews, such as one from Cycle magazine in 1980, praised the XS850 as an "excellent" motorcycle, highlighting its sufficient speed, smooth operation, good handling, strong brakes, and overall comfort.

Yamaha's Triple Legacy: From XS to FZ-09

Fast forward to the present, and Yamaha is once again making waves with its three-cylinder technology, most notably with the FZ-09. Introduced at a time when the Japanese motorcycle industry is often perceived as playing catch-up to the more aggressive European manufacturers, the FZ-09 aims to recapture the spirit of innovation and excitement that the XS750 and XS850 represented over three decades ago. The FZ-09, priced affordably, seeks to challenge not only its Japanese rivals but also established European triples from Triumph and MV Agusta.

Comparing the Generations: XS850 vs. FZ-09

The technological advancements between the XS850 and the FZ-09 are stark, reflecting nearly forty years of progress in engine design, materials, and manufacturing. The FZ-09 boasts an 847cc engine with a larger bore (78.0mm vs. 71.5mm) but a significantly shorter stroke (59.1mm vs. 68.6mm). Unlike the air-cooled XS engines, the FZ-09 features liquid cooling and four valves per cylinder (12 valves total), contributing to a much higher compression ratio of 11.5:1. Furthermore, carburetors have been replaced by sophisticated electronic fuel injection systems, offering precise control over the air-fuel mixture for optimal performance and emissions.

Perhaps one of the most dramatic improvements is in weight. Despite its larger engine, wider wheels and tires, and sophisticated emissions control systems, the FZ-09 tips the scales at a lithe 414 lbs (ready to ride). In stark contrast, the XS850 weighed a substantial 569 lbs (wet). This nearly 150 lb difference is a testament to modern engineering, showcasing advancements in frame design, material science, and component integration.

Frequently Asked Questions

Why was the Yamaha XS850 considered lean?

The Yamaha XS850 was considered lean due to its carburetion and exhaust systems being intentionally set up by the factory to meet stricter emissions regulations of the early 1980s. This resulted in a weaker performance output than its potential, often requiring aftermarket modifications to restore power.

Is the XS850 a good motorcycle?

Yes, the XS850 is generally considered a good motorcycle. It is known for its smooth triple-cylinder engine, comfortable ride, and capable handling, especially after riders made modifications to overcome the factory lean-jetting.

What made the XS850 smooth?

The smoothness of the XS850 was attributed to its well-balanced three-cylinder engine design, the use of rubber mounting for the handlebars and engine, and the inherent damping qualities of its chassis and suspension.

What happened to the Yamaha XS850SG Special?

The Yamaha XS850SG Special, like other models, was affected by the lean-jetting for emissions. However, it was also a capable machine, and owners often found ways to enhance its performance. Its "Special" designation usually indicated cosmetic differences or minor equipment upgrades.

What are the main differences between the XS750 and XS850?

The main differences lie in the XS850's larger bore, revised cylinder head, and the use of Hitachi carburetors jetted lean for emissions. The XS850 also featured air-assisted front forks, an upgrade from the XS750's standard adjustable forks.

The journey from the XS750 to the XS850, and now to the FZ-09, highlights Yamaha's consistent innovation and adaptation within the challenging landscape of motorcycle development. While the XS850 may have been "lean" by design due to regulations, its underlying engineering and the passion of its riders ensured its place as a memorable and capable machine in Yamaha's rich history. The legacy of smooth triples and engaging rides continues with Yamaha's modern offerings, proving that the tuning fork company's mastery of the three-cylinder configuration is far from over.

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