Yamaha TX500
Years produced: 1973-1978
Claimed power: 48hp @ 8,500rpm (claimed)
Top speed: 98mph (period test)
Engine type: 498cc air-cooled DOHC 8-valve parallel twin
Transmission: 5-speed
Weight: 456lbs (wet)
MPG: 40-55
Price then/now: $1,395 (1973)/$1,000-$2,500

In 1973, the motorcycle market hadn’t yet gone cubic inch crazy, and 500cc was still considered a generous size for a street bike. At the time, the lion’s share of motorcycles in the half-liter class were 2-strokes. While Yamaha had enjoyed considerable success with its RD250s and 350s, it needed a new machine to place between these and the TX650 twin (as the 650 had just been renamed), and their new flagship counter-balanced TX750 twin. The resulting Yamaha TX500 was Yamaha’s first foray into midsize 4-stroke territory, and while initial impressions were highly favorable, the TX500 proved less than easy to live with, perhaps because it was a little too high-tech for its time.

On paper it looked promising and bristled with innovation. The 180-degree, short-stroke parallel twin boasted dual overhead camshafts and four valves per cylinder for high-revving, class-leading power. Following in the footsteps of its big brother, the TX750, the TX500 twin used Yamaha’s “Omni-phase” balance shaft to quell the inevitable parallel twin buzzing. Mated to a 5-speed transmission with electric start and equipped with a front disc brake, this thoroughly modern engine made Triumph’s pushrod, 4-speed, kick start, drum-braked Daytona 500 look positively archaic.

TX500 styling was modern, too, with smoothly integrated engine castings, one-piece dash, sleek gas tank, upswept mufflers and plenty of chrome. The TX500 was comprehensively equipped, with an up-to-date electrical system well able to cope with the electric starter. Testers liked that a single key worked the ignition, steering lock, seat lock and gas filler cap. Yet with all its seeming improvements, the TX was a leap into uncharted territory.

Period test reports, while noting a relative lack of torque at low to mid revs, noted “a good blast of power” from the revvy engine and praised the bike’s slick-shifting transmission. The TX’s handling inspired confidence too; good ground clearance and overall balance made it easy to maintain a chosen line. However, testers found that cornering above 70mph could induce mild steering wobble, which while never dangerous could be a little disconcerting. Brakes, borrowed from the RD350, worked perfectly well, though the front disc required a firm pull and the rear was perhaps a little too powerful.

Unfortunately, things went slightly awry with power delivery. First, the engine was noticeably cold-blooded and needed a good warm up before it would run without the choke. And even when warm, at least one tester experienced problems with the engine sometimes dying when the throttle was backed off — not closed, just reduced. Other riders reported that if the engine was allowed to idle for a few seconds (at a traffic signal, for example), it had a bad habit of stalling when the throttle was cracked open. Testers also noted surging at small throttle openings, and blamed the Keihin CV carbs, noting that Honda had experienced similar issues with the same type on the CB450.