Yamaha TRX850

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Yamaha TRX 850
Manufacturer Yamaha Motor Company
Also called TRX
Production 1995 - 1999
Predecessor Yamaha TDM850
Successor None
Class Sport bike
Engine 850 cc parallel-twin
Transmission 5-speed manual
Wheelbase 1,435 mm
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.[1]

Design and development[edit]

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.[2] 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 Ducati 900SS which supposedly inspired the TRX850
A TRX850 with a black frame

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.[3] 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.[4] 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".[3] 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".[3]

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...".[5]

The 270° crankshaft[edit]

The 270° crank concept has been attributed to Australian Phil Irving of Vincent renown,[5] but the TRX was the first[6] 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".[7] Unlike 180° & 360° parallel-twins, a 270° engine that is running never has both pistons stationary, so flywheel momentum continues uninterrupted.[8] 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.[9]

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.[10] In 2015, MCN reported that the forthcoming Honda 1000cc Africa Twin would have a 270° engine.[11]

Owners' modifications[edit]

The indifferent OEM disc brake callipers may usefully be replaced with very effective "Blue-Spot" items.[12] 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.


  1. ^ "Yamaha TDM900 (2002-current) - Yamaha Motorcycle Reviews". Motorcyclenews.com. Retrieved 2011-12-27. 
  2. ^ "Yamaha TRX850 - Yamaha Wiki". Yamaha-tech.com. 2009-02-05. Retrieved 2011-12-27. 
  3. ^ a b c "Yamaha TRX850 (1996-2000) - Yamaha Motorcycle Reviews". Motorcyclenews.com. Retrieved 2011-12-27. 
  4. ^ (28 April 2010)
  5. ^ a b Motorcycle Monthly, April 2014
  6. ^ "Fast Bike" magazine August 1995 page 20
  7. ^ http://www.morebikes.co.uk/2013-yamaha-mt-07-used-bike/
  8. ^ http://www.motorcycle.com/manufacturer/yamaha/yamaha-trx-850-17077.html
  9. ^ 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. 
  10. ^ Motor Cycle News 28 Sept 2011 page 4
  11. ^ Motor Cycle News 20 MaY 2015
  12. ^ "12 of 12 Yamaha TRusefully X850 Sports Bike Reviews | Guest's Review". Review Centre. Retrieved 2011-12-27. 

External links[edit]