|Manufacturer||Yamaha Motor Company|
|Production||1995 - 1999|
|Engine||850 cc parallel-twin|
|Dimensions||L: 2,070 mm
W: 700 mm
|Seat height||795 mm|
|Weight||190 kg (dry)
|Fuel capacity||18 l|
The Yamaha TRX850 is a Yamaha sports motorcycle with a 10-valve dohc 849 cc 270° parallel-twin engine. It first appeared in Japan in 1995, and a version for the European market became available in 1996. Although developed cheaply from the factory's "parts bin" using a modified TDM850 engine and FZR cycle parts, the TRX performs well and has a coherent identity of its own.
Design and development
The TRX was designed to exploit the 1990s penchant for big twin-cylinder sportsbikes, and was aimed particularly at the 900 cc Ducati SuperSport V-twin, whose tubular trellis frame it mimicked. However, the TRX's price was high and it sold poorly in Europe, being overshadowed by faster and more sophisticated motorcycles such as the Honda VTR1000 and the Suzuki TL1000S. In 1999 Yamaha stopped making the TRX, but the TDM, enlarged to 900 cc, remains in production.
The TRX has five valves per cylinder: three inlet and two exhaust. The dry sump engine produces some 84 Nm of torque, and around 80 bhp. Unusually, the oil tank is not remote, but is integral to the engine, sitting atop the gearbox. This design eradicates external oil lines, gives faster oil warm-up, and simplifies manufacture. The shallow sump allows the engine to be sited lower, for an optimal CG position. The 360° crank of the original TDM became instead a 270° crank for both the TRX and for later TDMs.
Compared to the TDM, the TRX is lighter, lower and sportier. Its front forks are conventional telescopics, while the rear suspension is a rising-rate monoshock unit. The poor original disc brake callipers can be replaced with Yamaha's superior "Blue-Spot" items. The stock exhaust silencers are heavy and choke the output; so any TRX benefits from less constricting can units. The OE Michelin Macadams were hard-compound tyres that gave poor adhesion; popular replacement tyres include Michelin Pilots or Pirelli Diablo Stradas.
The TRX performs best as a solo machine, as it has poor provision for a pillion passenger, namely: very high pillion foot pegs, a small thin seat, and a token seat strap (rather than a proper grab rail).
The 270° crankshaft
The idea of a 270° crank is attributed to Australian Phil Irving of Vincent Motorcycles fame. The TRX was the first production parallel-twin motorcycle to feature a 270° crank. Its so-called “big-bang ignition sequence” yields the sound and feel of a V-twin. When running, unlike the 180° & 360° twins, a 270° engine never has both pistons stationary, so flywheel momentum is constant. In a parallel-twin, a 270° crank gives less vibration than a 360° crank, and has a more regular firing pattern than a 180° crank (or 90° V-twin). The 270° firing interval is still not perfectly even, and this slight unevenness is claimed to allow better power delivery to the rear tyre by giving two fairly close power pulses followed by a longer "recovery gap" which supposedly helps the tyre resume adhesion to the road. Both the 2009 Triumph Thunderbird and the "Donington" Norton Commando 961 are 270° designs, and arguably, the 270° crank is becoming the optimum configuration for large parallel-twins.
In Motorcycle News (MCN) the TRX was described as "the best-kept secret in motorcycling" and a "forgotten gem" which bore comparison with the 270° Norton Commando 961. The MCN review states: "The TRX produces less power than sports 600s of the same era, but it’s much gruntier and more satisfying to use thanks to that twin cylinder character". The review added: "The TRX is a cracking bike, ... a sporty motorcycle but road biased with tons of character. It's stable, handles neutrally and feels like a proper sports bike".
In an MCN readers' poll of the “Top Ten Big Twin Sports Bikes", the TRX came joint third, beaten only by the joint winners, the Ducati 916 & 748, with 90%. The TRX was rated at 88% (equal to the Ducati 996, Suzuki TL1000s & Honda SP-1). The TRX beat the Aprilia RSV1000 (86%), the Suzuki TL1000R (84%), the Honda Firestorm (82%) and the Aprilia Futura (80%).
In 2014, Steve Cooper wrote of the TRX: "Very much the thinking man's sports bike, this slightly oddball twin is beginning to reach cult status and for good reason; with a little work it's possible to see a genuine 100bhp..."
After 1999, Yamaha produced no obvious successor to the TRX. The 2013 Yamaha MT-09 partly fits the bill; and its designer, Shun Miyazawa, has said that the MT-09 will be the basis of further models which may include a TRX-style sportsbike/cafe-racer.
- "Yamaha TRX850 (1996-2000) - Yamaha Motorcycle Reviews". Motorcyclenews.com. Retrieved 2011-12-27.
- "Yamaha TDM900 (2002-current) - Yamaha Motorcycle Reviews". Motorcyclenews.com. Retrieved 2011-12-27.
- "Yamaha TRX850 - Yamaha Wiki". Yamaha-tech.com. 2009-02-05. Retrieved 2011-12-27.
- "12 of 12 Yamaha TRX850 Sports Bike Reviews | Guest's Review". Review Centre. Retrieved 2011-12-27.
- Motorcycle Monthly, April 2014
- "Fast Bike" magazine August 1995 page 20
- From a press release issued by Yamaha Motor Corp. U.S.A.: (2008-09-08). "Updated: 2009 Yamaha YZF-R1 Features Uneven Firing Order For Improved Power Delivery News Article //". Roadracingworld.com. Retrieved 2011-12-27.
- <Motor Cycle News 28 Sept 2011 page 4
- (28 April 2010)
- (20 May 2009)
- Motorcycle Monthly, April 2014
- MotorCycle News 4 September 2013, page 11
- Yamaha TRX850 review at Motorcycle.com