I have run my TRX850 up to 63000km now, I bought it as an 8k used Japanese import.
In general it’s a good solid all round reliable ride. Just as you’d expect from a well developed parts bin special based on the indestructible Yamaha Genesis motor.
In general the TRX850 only suffers from the same problems as any modern sports bike, ie: overpriced consumables. It’s a constant expensive domestic strain keeping it in tires, brakes and chains (in that order).
Having said that, there are some little things it’s handy to know. There was an update in 1998 to ‘cure’ some problems that ‘didn’t exist’.
Inlet valve stretching: if the pre 1998 motor is ridden very hard, the inlet valves may only last 20-30000km. In my case I used the available over-rev to save changing gear in the hills. Eventually I destroyed my inlet valves. The Yamaha valve part number changed in ’98 in such a way as to suggest a revision. There is a body of opinion that suggests minor changes to the valve closing ramp on the cam profile made necessary by increased overlap for the sports bike motor is the real root cause. I guess no-one outside Yamaha technical really knows or cares.
Gearbox backlash. Earlier bikes appear to have more backlash in 1st, 2nd and 3rd than later bikes. I believe Yamaha reduced this in ’98, but have no objective evidence to substantiate this. I do not believe this is a reliability problem, after all this is a version of the indestructible Yamaha Genesis/exup motor.
Clutch noise, hard take-offs from the lights can produce a really horrible noise. This never seems to cause or be an issue. Again the clutch is the same design as the exup motor, missing only the stabilising ring around the basket.
When servicing the valve clearances, correct tension (torque) on the cam bearing caps is critical, get it wrong and you’ll destroy your cams and head. $Ouch.
Oil consumption: Yamaha service limit is 1liter/1000km, (the same as an airhead BMW). Mine uses anywhere from 50ml to 800ml/1000 depending on how hard I’m riding. My philosophy is if the plugs aren’t fouling, don’t worry about it, just pour more in. I use Castrol 4T because I can mix anything available on the road with it (and I like the hexagon cap on the container).
There’s really no need to deactivate the Japanese market speed limiter. By 180km/hr the motor is not accelerating hard anymore, the budget suspension can’t really handle the cornering loads induced by that speed and you’d be bloody stupid to be riding like that on the road. On the track days I’ve done there are precious few straights where more speed is required given the relatively modest power output. Maybe Phillip Island, but those track days have priced themselves off the market now for likely owners of TRX’s in any case.
When the Japanese market odo cable breaks, engine management electronics’ rev limit the engine to 6000rpm in every gear. Your bike has not and will not blow up, just short-shift all the way home and/or until you can afford a new cable. A poor attempt at removing the speed limiter has the same result.
The TRX does not really carry enough weight on the front wheel. To allow for this, use soft compound sports tires, sport touring tires wear out FASTER due to all the sliding (D205 fronts last only 4500km!). It is kind of fun though...
TRX’s get great rear wheel traction, I suppose due to the 270 degree crank and slight rearward weight bias. This means sport touring tires are more-or-less adequate and last an extra 30% mileage.
Some useful tips for improvement in value-for-money order (let’s be realistic, if you’ve just bought a TX850 you’re operating on a budget. I know I am.):
1. Camel-back, keep hydrated. Water bottles don’t work because I never remember to drink from them.
2. 30mm spacer between the seat back stop and it’s mount. If you have a big fat ass, you can skip this one. For me it reduces ‘unexpected’ changes in weight distribution under throttle and brakes.
3. Fork springs. I have 3 sets. I learned the hard way to use one grade lighter than that recommended by the suspension gurus. I weigh 84kg and use .85kg/mm springs. You can achieve the same effect by cutting 5 coils off the std springs and making a spacer that gives 10mm preload with the adjuster wound right out. Do not cut off any more than this, the springs will coil bind and limit your travel.
4. Fork oil, don’t waste your money on gold valves (I’ve removed mine at great expense) or messing about with oil levels etc. Just get the springing correct and use SAE 10 fork oil. Change fork oil every time you change your front tire, it’s only $10 and you’re 2/3 way there once the wheel and caliper’s are out. Damping oil is subject to a lot of shear and frothing, both of which reduce viscosity and therefore damping effect.
5. Scottoiler. I get 30000km from each chain, my OEM rear sprocket did 60000km. Change your front sprocket every 7500km. I buy std O ring chains, all those X-rings and W-rings may have a value when you’re making 160hp, but the TRX doesn't, and your worn front sprocket will trash that expensive chain just as fast the cheap one. On my other bike, I use Castrol chain oil ($7.99 at supercheap) and lube it every 400km. Present chain/sprocket is 27000km and counting.
6. Hot grips. You can skip this one if you live in Qld/NT, everyone else needs them.
7. Ultra light exhaust. I have a 2-1 carbon can (on-line auction, $210!!!). No more power (more noise though), but the improvements in front wheel traction from getting around 8kg off the rear of the bike is similar to removing a weekends worth of camping gear...
8. Organic brake pads. Good feel, less rotor wear. The cheapest new rotors I could find at the time were $700 a pair. OEM’s only lasted 40000km. (I don’t have R1 brakes, the Japanese market brembos work fine and I need to save my money for tires).
9. Ohlins shock. This is really too expensive to consider if you’re buying a 2nd hand TRX. You could re-spring and re-valve your std shock I guess, but I really wanted an Ohlins. It’s great, done well over 50000km now and while overdue for a service it’s still responding well.
Overall a great bike. Practical (insofar as sports bikes ever are), tough competent etc. Don’t pay too much if you’re shopping. Australian red book price is around $4k. New equivalents are bikes like the SV650 with similar power and build quality, but only $10k new!