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1973 Yamaha TX750
|Manufacturer||Yamaha Motor Company|
|Parent company||Yamaha Corporation|
|Engine||743 cc (45.3 cu in) SOHC parallel twin|
|Top speed||95 miles per hour (153 km/h)|
|Power||63 horsepower (47 kW) @ 7,500rpm|
|Transmission||Five speed sequential|
|Weight||235 kilograms (518 lb) (wet)|
The TX750 was a Yamaha motorcycle made in 1973 and 1974. It was loosely based on the XS650 but had what Yamaha called an "Omni-Phase balancer" to counter vibrations which are inherent in a parallel twin with the crankshaft set at 360 degrees (both pistons rise at the same time). Using a pair of balancers (one to stabilize the imbalance of the cylinders, the other to counter the rocking caused by the first balancer), Yamaha’s Omni-Phase balancer essentially eliminated vibration in the TX750, producing a smooth ride previously thought possible only in a triple or a four cylinder. This new system was a first for a motorcycle but resulted in massive failures for the first model year. Although, these problems were fixed in 1974 sales never picked up and the machine was shelved.
Cycle World magazine, in their October 1972 issue positively reviewed the concept when they wrote: "The result is smoothness beyond belief," . "Shut your eyes and you are on a four. It couldn’t be a twin." In addition, the bike was set up with a single front disc brake with provision to install a second one on the other side. European machines were delivered with twin disc brakes from the factory. The bike also had an interesting warning light system with a brake pad wear indicator, a first for a motorcycle.
The bike was popular at first but soon reliability problems began to emerge and the problems lay with the Omni-Phase balancer: At high rpm the balance weights would whip oil in the sump into a froth, aerating the oil and starving the crank for lubrication which resulted in bearing failure.
In addition, the balance chain would stretch, resulting with the counterweights being out of phase and making the engine run rough. Although Yamaha quickly repaired the problems, including a deeper sump and an adjustable balance chain, sales fell and the TX750 became synonymous with poor design and reliability. The 1974 Model was extensively modified with a revised sump and does not suffer from reliability issues.
- Holliday, Bob (1974), Motorcycle panorama: a pictorial review of design and development, Newton Abbot, p. 108, ISBN 978-0-668-03647-4
- Richard Backus (November–December 2008). "1973-1974 Yamaha TX750". Motorcycle Classics. Retrieved 2009-08-10.
- Richard Backus (November–December 2007). "The Yamaha TX750". Motorcycle Classics. Retrieved 2011-10-04.