Yamaha TRX850
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| 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 sports motorcycle with a 10-valve dohc 849 cc 270° parallel-twin engine. Yamaha first released it 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]
Contents
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.[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 is essentially 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.
Reception
The TRX was designed to compete in the market with the Ducati 900SS V-twin, whose tubular trellis frame it mimicked.[3] Although developed cheaply from Yamaha's "parts bin", using a modified TDM850 engine and FZR cycle parts, the TRX performs well and has a coherent identity of its own.[4]
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.[5] 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".[4] The review added: "The TRX is a cracking bike, a sporty motorcycle with tons of character. It's stable, handles neutrally and feels like a proper sports bike".[4]
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...".[6]
Although considerably cheaper than the Ducati,[7] TRX sales were disappointing, and production ceased in 1999. The bike has since achieved a latter-day popularity, but there has been no obvious successor. However, in June 2015, Shinya Kimura designed a cafe racer special, commissioned by Yamaha. Called "Faster Son", it is based on the Yamaha MT-07 700cc parallel-twin and the new bike was unveiled at the Motorcycle Live show at the 2015 National Exhibition Centre in Birmingham, England..[8]
The 270° crankshaft
The TRX was the first[9] production motorcycle to feature a 270° crank. The 270° concept has been attributed to Australian Phil Irving (of Vincent renown)[6] and the design has proved an ideal compromise for the parallel-twin layout. The 270° crank has an ignition sequence and an engine balance that yields something of the feel of a V-twin.
When running, and unlike 180° & 360° parallel-twins, a 270° engine never has both pistons stationary, so its flywheel momentum is uninterrupted.[10] With less vibration than a 360° crank, and a more regular firing pattern than a 180° crank, a 270° crank results in a smoother engine. Any residual unevenness of the 270° firing interval has been claimed to deliver power to the rear tyre more effectively.[11]
Arguably, the 270° crank is becoming the optimal configuration for large parallel-twins.[12] The 2009 Triumph Thunderbird, the "Donington" Norton Commando 961, and the Yamaha MT-07 are all 270° designs. The 2016 Honda 1000cc Africa Twin has a 270° engine,[13] (rather than the V-twin of earlier incarnations) and the KTM 800cc parallel-twin roadster would also be a 270° design.[14] Bucking the trend, the short-lived 2001 MZ 1000S was a 180° twin;[15] but despite having balance shafts, the MZ engine still exhibited some vibration.[16]
Owners' modifications
The indifferent OEM disc brake callipers may usefully be replaced with very effective "Blue-Spot" items.[17] Stock exhaust silencers are heavy and constrictive, but after-market exhaust cans will boost power. Hard-compound OEM Michelin Macadams tyres gave poor adhesion, and softer alternatives have proved more suitable. The rather basic damper-rod forks are softly-sprung, and they benefit from heavier springs and improved damping.
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ "Performance Bikes" - October 1996 - pp118=124
- ↑ 4.0 4.1 4.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ (28 April 2010)
- ↑ 6.0 6.1 Motorcycle Monthly, April 2014
- ↑ "Performance Bikes" - October 1996 - pp118=124
- ↑ Motor Cycle News 17 June 2015
- ↑ "Fast Bike" magazine August 1995 page 20
- ↑ http://www.motorcycle.com/manufacturer/yamaha/yamaha-trx-850-17077.html
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Motor Cycle News 28 Sept 2011 page 4
- ↑ Motor Cycle News 20 May 2015
- ↑ Motor Cycle News 26 August 2015
- ↑ MZ 1000S Spares Catalogue
- ↑ Motorcycle USA review 2004
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
External links
- Yamaha TRX850 review at Motorcycle.com
