|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. The TRX is lighter, lower and sportier than its stablemate, the TDM850; but in 1999 Yamaha stopped making the TRX, while the TDM series, enlarged to 900 cc, remains in production.
Design and development
The TRX engine has five valves per cylinder, three inlet and two exhaust. It produces some 84 Nm of torque and around 80 bhp. Unusually for a dry sump design, the oil tank is not remote, but is integral to the engine, sitting atop the gearbox. This feature 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 was changed to a 270° crank for both the TRX and later TDMs. The engine has a balance shaft to smooth out vibrations.The conventional telescopic front forks have clip-on handlebars, and the rear suspension is a rising-rate monoshock unit.
The TRX arguably serves best as a solo machine, having meagre provision for a pillion passenger, namely uncomfortably high pillion foot pegs, a thin pillion seat, and only a token seat strap.
The TRX was designed to compete in the market with the Ducati 900SS V-twin, whose tubular trellis frame it mimicked. 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. However, the TRX's price was high and it sold poorly in Europe.
In Motorcycle News (MCN) the TRX was later 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 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...".
The 270° crankshaft
The 270° crank concept has been attributed to Australian Phil Irving of Vincent renown, but the TRX was the first production motorcycle to feature a 270° crank. Its ignition sequence yields something of the feel of a V-twin.
The 270° engine has been called the "Goldilocks option". Unlike 180° & 360° parallel-twins, a 270° engine that is running never has both pistons stationary, so flywheel momentum continues uninterrupted. A 270° crank gives less vibration than a 360° crank, and has a more regular firing pattern than a 180° crank. The residual unevenness of the 270° firing interval is claimed to deliver power to the rear tyre more effectively.
The 2009 Triumph Thunderbird, the "Donington" Norton Commando 961, and the Yamaha MT-07 are all 270° designs, and arguably, the 270° crank is becoming the optimum configuration for large parallel-twins. In 2015, MCN reported that the forthcoming Honda 1000cc Africa Twin would have a 270° engine.
The indifferent OEM disc brake callipers may usefully be replaced with very effective "Blue-Spot" items. Stock exhaust silencers are heavy and constrictive, but after-market exhaust cans will boost power. Hard-compound OEM Michelin Macadams tyres gave poor adhesion, but softer replacements have proved suitable.
- "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.
- "Yamaha TRX850 (1996-2000) - Yamaha Motorcycle Reviews". Motorcyclenews.com. Retrieved 2011-12-27.
- (28 April 2010)
- 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
- Motor Cycle News 20 MaY 2015
- "12 of 12 Yamaha TRusefully X850 Sports Bike Reviews | Guest's Review". Review Centre. Retrieved 2011-12-27.
- Yamaha TRX850 review at Motorcycle.com