Sport-Touring.Net - Motorcyclist Magazine Review of 1992 TDM 850

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I see by your outfit that you are a spaceman...

The YAMAHA TDM850

Want to have a little fun? Park Yamaha's TDM850 at the local sunday-morning motorhead hangout and just listen. Somewhere between the caffein and the lies you'll hear sport-bike guys call it some Paris-Dakar refugee. The Harley boys roll their eyes and enlist it as unimpeachable evidence that somebody at Yamaha is more than a few sandwiches shy of a picnic. And while the dual-sport guys are wishing for knobbies, the surfers stopping in on their way to the waves haven't a clue what to call it. But they like it.

The TDM is like that, it bends the rules, refusing to fit into any prescribed category. You can't call it a sport-bike. It isn't a dual-sport in the traditional sense. It's cool enough to cruise but it sure isn't a cruiser. Add some soft luggage and you could pull off a tour, but it isn't a touring bike either. What it is, in Yamaha parlance at least, is a 'new sports' motorcycle: something that does just about anything you'd ask a motorcycle to do while smashing the status quo into a billion pieces.

Think of the TDM as a post super-sport: a motorcycle aimed at the hard-core enthusiasts with a waning interest in wrapping their thirty-somethingish frames around anything in the FZR-GSXR-CBR-ZX genre again.
Yamaha's research pegs the prospective TDM buyer as a rider between 35 and 45 years old who started thinking about motorcycles shortly after stepping up to solid food. He or she has owned sport-bikes and dirt-bikes and likely has one of each in the garage.

The TDM hits the ball right through the heart of that demographic wicket. It's both visually and mechanically exciting; it's sporty without being painfully racy. It's also comfortable, practical and flexible enough to be as good at the Monday-through-Friday reality as it is escaping to the mountains for a weekend. But to appreciate the TDM's true appeal you need to take a close look at its heart and bones.

PARIS TO PEORIA
The TDM's 849cc liquid-cooled engine carries a more impressive technological resume than any other Japanese twin. Basically, it's a bored and stroked version of Yamaha's European-issue Paris-Dakar poseur, the 750cc Super Tenere. Cylinders lean 35 degrees forward, giving the twin 38mm constant-velocity carburetors a straight shot to the five-valve (three intakes, two exhausts) Genesis tech combustion chambers. Yamaha's usual TCI digital ignition system provides the spark.

Compression is set at a relatively mild 9.2:1. Cam timing is short on overlap and duration to create a flat, torque-laden power curve. Still, for a bike from the land of the five-figure rev limit, the the TDM's 8,000-rpm redline seems a bit pedestrian --- until you punch up the calculator and find it's pistons are moving 3543 feet per minute at that crank speed. Compare that with 3776 feet per minute for an FZR600 at it's 10,500-rpm power peak and you see the longer stroke twin is actually moving right along. To keep those two 89.5mm pistons that are hammering up and down on a 360 degree crank from shaking the works to bits, the TDM spins twin gear-driven counterbalancers in front and behind the crankshaft. The rubber-mounted handlebar and footpegs help as well.

Engine architecture makes the most efficient use of available space. By staggering transmission shafts relative to the crank and opting for dry-sump lubrication (engine oil rides in a tank under the seat), Yamaha engineers kept the big twin relatively compact. Up top, twin cams cue the valves through a shim-under-bucket arrangement. The bad news is those cams must come out to adjust valve lash. The good news is this scheme puts an astonishing 26,600 miles between valve-lash adjustments.

The engine hangs stressed-member style in a steel version of Yamaha's familiar twin-spar Deltabox chassis. Out back, a plain vanilla, box-section steel swingarm bolts directly to the lone rear shockwhich is adjustable for spring preload and 15 different rebound-damping settings. There's no rising-rate linkage here, but the KYB shock gets gets a switchable dual-spring arrangement that bypasses the softer of the two for passenger-packing. Just pop off the seat and flip the adjuster atop the shock body from soft to hard, and you have effectively swapped springs instead of just upping spring preload. We found it to be a real plus for wallow-free two-up travel. Up front the 41mm cartridge-type fork has screw-type spring-preload adjusters and a choice of six positions for rebound damping.

SIT UP STRAIGHT
Throw a leg over Yamaha's avant-garde twin, and the first thing you notice is that you are straddling a tall motorcycle. The curvaceous 4.8 gallon fuel tank hitshits most folks above the belt, but a (relatively) managable 31.6 inch seat height lets all but the shortest riders plant both boots on the terra. The wide, swept-back handlebar and relatively low footpegs allow an upright, natural riding posture that's refreshingly humane after the fetal tuck enforced by most racer-replicas. Our 6 foot, 4 inch feature editor pronounced it his favorite sporting ergonomic package of the year.

From any rider's view, the cockpit is nicely finished. Levers and switch gear are the usual excellent Yamaha fare. The centrally placed tach is flanked by a matching speedo with the obligatory idiot-light array placed below and to the right, instead of up top where it can best catch your eye. Instrumentation is complete except for the conspicuous absence of an oil-level or oil-pressure warning light. Best to keep current with the dipstick in the under-seat oil tank, although there is no centerstand to simplify that chore -- or tire changes.

The TDM is quite cooperative when it's time to get underway. Pull out the oddly placed choke plunger, located below the left frame rail, thumb the starter, and the twin spins to life. But anybody expecting internal-combustion drama on the order of a Triumph or Ducati twin will be sorely dissapointed. The tinny whisper escaping the twin muffler cannisters caries all the brio of the family Briggs & Stratton. This one gets a tastefully muted Team Stealth round of applause. Unfortunately, so does the horn, perhaps the worst we've barely heard.

A slightly lumpy idle is the only clue you're straddling a 360 degree twin instead of a triple or a four. Once the revs spin up, the counterbalancers all but erase vibration. Aside from an annoying off-idle dead spot, rolling open the throttle releases power in a seamless, almost electric rush from 2,000 rpm. You won't find yourself shifting much around town, and that's good. From the crankshaft back the TDM's powertrain is dissapointing. There's more driveline slack than we would have liked, and the five-speed transmission feels stiff and balky. It takes a practiced toe on the shifter to cue up the next gear instead of a false nuetral. The cable-actuated clutch is more cooperative, though it doesn't engage till the last bit of lever travel and gets a bit grabby when hot.

Still the TDM feels light and athletic through most miserable city traffic. At anything above a walking pace, it's far more nimble than you would expect a 509 pound motorcycle to be. Sitting higher than on a cruiser and more upright than on a sport bike the TDM rider stands a better chance of seeing and being seen while stalking gridlocked city streets.

The Yamaha is just as comfortable once you segue to the interstate. Turning 3600 rpm into an easy 70 mph, the long-legged TDM feels as smooth as a four. At a steady 70, the engine barely sips unleaded, calling up the switch to the reserve tap every 200 miles. A steady throttle hand can squeeze 60 miles from a gallon of gas on a carm day; ridden hard, the TDM will last 150 miles on a tankful.

Trolling down the interstate near the legal limit, rearview images are crystal-clear, with only the slightest low-frequency rumble sneaking through the handlebar and footpegs. Aside from a fuzzy spell between 4,000 and 5,000 rpm, the counterbalanced twin is a reasonably smooth power source.

HOW IT FEELS
The marvelously roomy ergonomic package makes the TDM an enjoyable mount for all-day horizon chasing, although the downward slope of the wide saddle seems like Mt. Nererest after 500 miles. The nicely sculpted fairing steers most of the wind around your hands and upper torso, though taller riders found found their arms and shoulders fighting the breeze. An annoying amount of turbulence buffets the tallest riders' helmets, especially heading into a stiff wind. After a few hundred miles bucking a head wind. our tallest tester began thinking of evil ways to dispose of the abbreviated stock windscreen. A reshaped aftermarket alternative could make a major improvement, but sub-six footers had fewer problems.

The TDM's passenger accomodations are not quite as roomy as the rider's. Still, our our carefully calibrated test passengers found the ample seat and artistic grab rail-luggage rack made the ride quite comfy by sport bike standards. By any measure, the twin quartz halogen headlamps blow a comfortably long, broad, well-shaped hole in the darkness, adding a generous measure of confidence to after-dark sorties.

Exit onto your favorite twisty bits, and the TDM engine delivers power more like a smooth 850cc single than a twin. Don't expect the cammy rush of an FZR600; there's no discernible powerband here, just more muscle in a straight trace from idle to the 8,000 rpm redline. Keep the tachometer above 3000 rpm, and the TDM squirts effortlessly out of tight corners. That Kansas-flat torque curve means even the tightest roads are rarely more than a two gear proposition. Smooth, quick progress is ridiculously easy, unless the tach needle drops below 2000 rpm. Then the off-idle carbuation glitch conspires with the excess driveline lash to make on-off throttle transitions an annoying lurch-and-jerk fest.

Though ample ground clearance and light steering effort let you get down any bit of serpentine pavement with admirable haste, the TDM's cornering manners lean towards stability. With it's mass centered higher than any racer-boy replica, the tall twin can't respond to quick-flick steering instructions with the speed of a sport bike. Although it carries the same 25 degrees of rake as Honda's benchmark CBR600F2, the Yamaha's do-it-all steering geometry is skewed towards stability with 4.1 inches of trail -- nearly half an inch more than the smaller CBR. Balance that on a 58.6 inch wheelbase (nearly 3 inches longer than the CBR) led by an 18 inch front wheel and you have a motorcycle that's happier banking through long sweeping bends than short tight ones.

FINE-TUNING
Through a relatively broad adjustment band at either end lets you tailor the ride to just about any road or rider, TDM suspension favors a comfortable, compliant ride at sub-warp speeds over racetrack-style surfaces. Stiffening shock preload by a three-quarter to to full turn on the threaded collar-type adjuster delivered a reasonably smooth ride with enough stability and cornering clearance for spirited riding. But we found flicking the spring selector from soft to hard once we'd set spring preload to taste delivered an uncomfortably firm solo ride. The hard position works best to to tailor the shock quickly for passenger packing. The rebound damping collar at the bottom of the shock body is easily adjustable although we set ours at maximum and wished for a bit more.

The 41mm KYB fork does a good job on most surfaces, but diabolically bumpy roads quickly eat up the fork's soft initial travel, letting sharp, square-edged jolts pass through almost undiminished. We set spring preload on the second or the third of the TDM's five marked positions, with the rebound damping adjuster three or four (of six) out to maintain compliance without letting the bike wallow or dive excessively under heavy braking.

In the decelleration department , a pair of quad-piston calipers from Sumitomo grip 298mm floating rotors firmly enough to put a sliver of daylight between the rear wheel and the pavement under maximum braking or lock the front wheel with a two-finger grip. Both feel and fade-resistance are exemplarary. The combination of 245mm rear disc and dual piston caliper is long on power but a bit too lock-prone for our taste. Since the TDM's wheels are a bit too narrow to get the best from modern low-profile radials, they're shod with bias-ply Dunlop K505's. Aside from a bit of nervousness in deep rain grooves and a tendency to get a bit slippery at the limit, the Dunlops are perfectly adequate for 95% of the riders 95% of the time. There's traction enough to grind the footpeg feelers clean off in a day of hard riding. And though our five-percenters would have ordered up stickier tires, all of us wished for the smoother ride radials deliver over rippled pavement.

After a 3000 mile test gauntlet encompassing assorted peg-grinding proficiency sorties through the mountains, a 1000 mile lost weekend up the california coastline , Monday-through-Friday commuting and even a little dirt-road chicanery just for fun, the TDM tallied a near-perfect score. The only blemishes on it's report card were the clunky transmission, a choke cable that rusted shut after a couple of nights at the beach (nothing a little WD-40 couldn't fix) and a blown left-fork seal. The TDM didn't burn or leak oil. Heck, the chain barely stretched enough to need tightening.

So here's the deal. With the possible exception of roadracing and dual-sport work, the TDM is capable anything most rider's expect from a motorcycle. But even when it's wrapped in such an avant-garde package , such adaptability probably isn't enough to generate showroom super-stardom... yet. Yamaha keeps the lights turned on by selling stacks of FZR600's and SecaII's. Any marketing geniys woorth that corner office knows the TDM is an eclectic, slightly eccentric small-numbers motorcycle that appeals to a very specific, hard-core rider.

Is it a new direction for the next generation of sporting motorcycles or just a dead end? That question remains to be answered on showroom floors across the U.S. and Europe. Either way, bless Yamaha for taking a chance. The TDM's $6,599 sticker price puts it a full $1,800 over Suzuki's VX800 and $1,391 under the only vaguely comparable twin on the market: BMW's R100R Roadster.

In the end, the TDM850 has the least enviable slot in the showroom. By refusing to slip neatly into a single category, it competes indirectly with the bikes in almost every category. But if you want one motorcycle to work like a garageful and look like absolutely nothing else in the world, you're looking in the right place.
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Motorcyclist Magazine, August 1992, Issue 1144.

Topic: Motorcyclist Magazine Review of 1992 TDM 850 (Read 15902 times)