Remembering the TX750, Yamaha’s Failed Attempt at Keeping Big Twins Relevant in the ‘70s

While companies like Honda and Kawasaki were killing the inline-four game, Yamaha was hoping to prolong the popularity of two-cylinder bikes with the TX750. In order to address the inherent vibration issues of parallel-twins, the manufacturer devised a counter-balancing setup known as the Omni-Phase Balancer, which was intended to make the engine as smooth as a four-banger.

Clever though it may seem, this apparatus would actually end up being the TX750’s demise, as it had a tendency to aerate and overheat the motor oil at high rpm. The frothy fluid couldn’t be recirculated properly, leading to mechanical failures and a lot of disappointed customers. To add insult to injury, even the vibration problem that led to the OPB’s development was only half-solved.

Due to the searing heat of the oil, the chain hosting these balance weights would begin to stretch under load, consequently upsetting their delicate timing and making the engine shake like a belly dancer’s hips. Yet another nail in this creature’s coffin was the 1972 Castrol Six-Hour Production Race held at Amaroo Park in Australia.

As many as six TX750s entered the event, but only half of them have actually crossed the finish line and none took the podium. Plagued with reliability issues, these experimental twin-cylinder specimens were far from creating the impression that Yamaha would’ve hoped for. On the contrary, their performance during the event could only be described as embarrassing, and things weren’t looking brighter for the production models, either.

For the 1974 model-year, Yamaha’s engineers did fix pretty much everything that was wrong with the Omni-Phase mechanism, but the TX750’s reputation was already doomed in the eyes of the public. The ill-fated nameplate was discontinued shortly after, thus ending its disappointing two-year production run once and for all.

It isn’t known how many units were assembled in total, though it’s fairly safe to assume that number must be low. If you were to make a judgment based solely on its spec sheet, even a 1973 variant like the one pictured above might come across as a decent machine.

The specimen’s power source is an air-cooled 743cc parallel-twin featuring dry sump lubrication, dual constant-velocity Mikuni carbs and four valves operated via a single overhead camshaft. By delivering up to 63 hp and 51 pound-feet (69 Nm) of torque at the crank, the four-stroke mill allows the TX750 to achieve a top speed of 116 mph (186 kph).

Since these bikes are so rare, they still manage to capture the attention of some collectors and everyday riders despite their flaws, which is why we need to have a word with you about the exemplar shown in these photos. This ‘73 MY artifact is listed on Bring a Trailer with 8k miles (13,000 km) under its belt, and the no-reserve auction will end on May 31.

Before showing up on the BaT platform, Yamaha’s antique fiend received Kenda Challenger tires, modern spark plugs and fresh fork seals. The motorcycle’s fuel petcock was replaced with an aftermarket module, while its voltage regulator has been readjusted and the carburetors got treated to a thorough scrub. Lastly, the selling dealer had this TX750’s starter clutch rebuilt for good measure.