YAMAHA TX500
Steve Cooper’s buyer’s guide on this quirky twin.
Within the quartet of Japanese motorcycle manufacturers we commonly refer to as The Big Four, Yamaha plays a different game to the other three.
It’s recognised by those that know these things that the tuning fork brand is edgier in its outlook, more inclined to take risks and, ultimately, has more than a touch of the maverick about it. When Yamaha gets an idea right it’s normally so damn good it cuts the legs out from under everyone else. Think LC350, Powervalves, EXUP systems, Deltabox frames and you’ll know what I mean. From the outset Yamaha’s concept specialists and designers challenged accepted principles and traditional engineering wisdom. The company’s sights were always set on beating Honda at its own game and in doing so followed lateral thought to its ultimate conclusion. Back in the late 1960s, few would have foreseen that two-strokes would become pariahs. Yamaha’s nascent XS650 was built to beat the Brits at their own game not save the planet. However as the decade flipped over, rumours became emergent facts which in turn morphed into embryonic legislation. Yamaha needed four-strokes and fast; California was getting jittery about emissions. A whole run of four-strokes was planned but they’d be unlike anything offered by The Big Aitch. Yamaha’s boffins had fallen in love with the concept of engine balancers. In theory and on paper if the various
linear forces within an engine are counteracted in some manner it can be made to run much smoother. Yamaha hadn’t discovered anything new; the engine balancer was first patented by Fredrick Lanchester in 1904 but motorcycle manufacturers had tended not to bother with them. Yamaha saw an angle here with the possibility of producing twins that could be as smooth as Honda fours. The first Yamaha to feature such a system was the TX750 which we’ll revisit at some point but the second machine in an envisaged wider family was the TX500. Yamaha opted for a 180º crank on the half-litre twin. Utilising a contra-rotating balance shaft the all-new twin ran a cam chain on the right-hand side of the engine with a geared-down, indirect, pick-up on the crank. This in turn allowed smaller cam sprockets to be used thus reducing the height of the cam box and thereby the engine. Buoyed by their own lateral thinking the R&D guys then designed the cylinder head to run four valves per cylinder. Prototype testing showed potential and, as expected, the engine was smoother than a large four-stroke twin had any right to be; it was time to launch the bike. April 1973 and the press eagerly awaited the new twin. Styling was based around the 1973 TX750 and TX650 and arguably streets ahead of anything from Honda. Upswept exhausts, dual piston actuated front disc(s), clean lines and decent colour options all suggested the new 500 would be something rather special. Compared to Honda’s then-aging CB450 it was, and the TX was certainly a match for it. What it didn’t do was outperform the supposed antediluvian and primordial Triumph T100 aka the Daytona. On paper the Yamaha made a claimed 40 horses but this translated to a genuine 38 at the rear wheel. The Daytona had 41bhp and weighed in at around 350lb; the TX500 was at least 20% heavier! Even if it was infinitely smoother than the Meriden twin the new Yamaha was beginning to look a whole lot less attractive and then customer fickleness, Yamaha’s own engineers and the EPA really delivered triple body blows. Customers wanted speed and didn’t care about the environment, Yamaha launched the seminal RD350 with 37bhp and the EPA subtly backpedalled on the introduction of lower emissions. Suddenly the Yamaha looked like it had just scored an own goal… and then it got a whole lot worse. The TX500 had not been tested enough and certain issues showed up (see What Goes Wrong). Unwilling to ditch another four-stroke twin (the TX750 was given an early Viking funeral) Yamaha persevered with the TX – modifying and updating it, renaming it the XS500 and in various guises continued making it until 1979-1980 but it was never a huge seller. The later models, not covered here, are overtly boxy and slab-sided analogues of the contemporary RD400S. Today the TX and early XS500 offer a mid-1970s alternative to two-strokes in general and Hondas in particular. The curved flowing styling of the pre ’76 models is both stylish and graceful, reliability is not as bad as folklore suggests and, if you fancy something a little different, it’ll make for an
interesting and involving project. If you want to go fast on a Japanese 500 twin buy a modern Honda CB500 but if back lanes riding and the odd longer distance A-road trip are your thing a decent TX500 might very well fit the bill. Handling for a bike of its age is better than average and the chassis is Rd250/350-based so comes with a pedigree. Oh and they need at least 7000rpm to get a wiggle on but then they make a glorious sound!