The Motorbike Archives

This year's IT465 is still a dynamite playbike, for it has even more docile power than last year's 425 and a more useable chassis as well. But what this IT has that the others never had is a more serious side. When the trail gets tough and time is short the IT can shift easily from play to serious mode. It only takes a more aggressive riding style to turn the IT465 into one of the best enduro bikes money can buy.

One reason the IT is more serious is because Yamaha is no longer bolting together old motocross technology. Instead, the IT465 utilized Yamaha's latest off-road designs to make it more like a YZ than any previous model.

Everywhere you look, the IT has undergone major or minor changes to make it more formidable. From the updated suspension and YZ frame to a quick-detach front light, the IT has expensive features that help it stay well inside its enduro minute. And with its awe-inspiring monster of a motor, the IT465 has the right amount of power for every occasion, no matter if you're plonking along a hillside trail or blasting down a dusty fireroad. It can, if you wish, be so blisteringly fast that you'll swear you're on a YZ; but thanks to revised motocross porting and a new exhaust, the 465 also serves as a forgiving playbike. The old 425 motor never worked so perfectly at both these extremes of performance, which is why so many serious riders chose to modify last year's big YZ to enduro trim rather than battle with an IT425.

That was fine last year, but without a wide-ratio gearbox and the new exhaust system, a converted YZ could never be a match for the IT465. Sheer size alone would seem to make the new engine better than the 425, but with a stroke that's a full seven millimeters longer, the motor has a totally different feel. Like the YZ from which it was cloned, the IT has an unhurried, almost effortless feel to it. There is no real need to rev the motor very high, and even less need to shift gears very often.

That's because the first signs of usable power show up about the time the first signs of noise come rumbling out of the muffler, and it just gets better from that point onward. The motor actually behaves like a latter-day four-stroke in that it will plonk down to idle like the biggest thumpers and then rev to the limit like a two-stroke motocrosser. And in between these extremes the Yamaha has a torque curve as flat as the desert to which the old 425 was so perfectly suited. Open the throttle and you feel as if you've been fired from an enormous catapult. It's as though uncovering the Mikuni's 38mm venturi releases a giant rubber band that launches you for ward in a smooth but sudden rush.

No mechanical tricks account for this amazing spread of power. Yamaha has simply taken its latest motocross technology and carefully adapted it to enduro use. A look inside the engine might even convince you that it is identical to the YZ. Certainly the outer cases, cylinder and head are unchanged, and there's not even a heavier ignition flywheel for a smoother spread of power. But a few small internal changes make all the difference.

Lowering the top edge of the exhaust port by 2mm and narrowing the transfers by the same amount accounts for the main horsepower shift. And a lengthier intake skirt gives the enduro's piston a longer service life than the YZ's. Yamaha also employed a longer header pipe and a larger-volume expansion chamber to improve low-speed performance. Back-pressure from a non-repackable silencer/spark arrestor further helps shift the power emphasis to the middle and lower end of the rpm scale.

As a result of these changes, the woods racer develops its power peak 500 rpm lower than the YZ motocrosser. But more importantly, even though the IT generates fractionally less peak horsepower than the YZ, its peak torque barely changes over a 2500-rpm spread while the YZ's torque peaks out rather abruptly.

To make the best use of this new stump-pulling power, Yamaha has fitted wider gear ratios for enduro use. First gear is lower than the YZ's, and its use is mandatory only when you play observed trials games. Second and third are retained from the YZ, while fourth and fifth are new, taller gears for fast fireroading. Combined with its smaller rear sprocket, the IT465 was able to plonk along like a true trials bike and still scream up to 88 mph.

For most enduros you won't need that sort of speed. Chances are, you won't use first or second gears much, either. The gearbox is a little imprecise and notchy anyway, so it's probably good that third and fourth gears handle almost any situation. Having such a wide power spread makes the IT almost like an automatic, and that is what makes it such a pleasant playbike as well as a good enduro mount. You simply snick into third gear and forget about everything but the trail ahead. You can bounce along rocky stream beds and climb almost impossible hills in third gear without rowing the shift lever or bogging the motor. The flat torque curve lets the revs drop until you can count the power pulses through the rubber-mounted handlebars. And when the trail opens out, you can use the motor right up to its 8000-rpm redline. You will, admittedly, feel it tingle through the high-mounted footpegs, but vibration is not a real problem with the IT. You always know it's there, but it is only bad when you first pump the cold motor into life with the awkward kickstarter. As it burbles alive on its rich mixture, the 465 shakes like a jackhammer, but once cleared out the vibes are held at an acceptable level.

Yamaha broke with Japanese tradition to insure that all the IT's amazing power could be used. The designers opted for a massive 17-inch IRC rear tire which, combined with a conventional IRC up front, gave exceptional straight-line stability.

Serious new suspension also helps keep the power hooked up to the ground. The enormous rear wheel is controlled by a 1981 YZ monoshock modified by an internal spacer that limits wheel travel to 11.4 inches. Damping is also altered for enduro use, with softer settings and a full 28 usable adjustment positions. Spring rate is changed, too, with a softer initial rate, but surprisingly, the IT's progressively wound spring has a higher final rate than the YZ's.

IT and YZ also differ at the front, where the only obvious cost-cutting on the IT shows up. It uses last year's 38mm motocross fork instead of the new 43mm units. Yet, when the fork was set to factory specifications with stock oil and no air, the front end was plush. The response on little bumps was very smooth indeed, and the fork rarely bottomed. In fact, the equally plush rear end often bottomed at the same time as the front over big, rolling whoops. However, both ends always reached full compression with a hydraulic thud rather than a harsh metallic clang.

Yamaha seems to have bracketed the ideal rear-suspension settings perfectly with its 28 damping adjustments. Our 180-pound tester used the stock spring preload and the damping set eight clicks from the hardest setting. That leaves lighter riders with enough damping and spring preload adjustments to suit almost any situation.

There are no areas where the IT suspension really falls short. Not even the older fork is overtaxed by large rocks or tree stumps. And almost 12 inches of ground clearance lets the Yamaha glide over most obstacles easily. The only problem we did have in gnarly sections was with the exhaust system. The header pipe has a curious routing that pokes it way out to the right of the motorcycle. And while it doesn't stick down as far as the old 425 version, it's more vulnerable. The first big rock it went over left a deep ding in the pipe, and a number of other boulders just made the situation worse. There appears to be no way of rerouting the pipe in its present form, so it might just be that regular exhaust repairs are the price for such a broad spread of power.

The rest of the motor is better protected from damage. Like Husqvarna, Yamaha uses a central frame rail added to its motocross chassis to protect the crankcases. The IT also has short bolt-on side tubes to protect the mag and clutch cases. The tubing is just as efficient at preventing damage as the aluminum bash plate used on previous ITs. An added advantage is that the tubing does not collect mud and water as does the skidplate, and that can make the IT a few pounds lighter at the end of a long enduro. Apart from the addition of a rear frame loop to support the fender and tool pouch, the IT chassis is identical to this year's YZ. In spite of a one-degree-steeper head angle than last year's IT, the 465 frame still fosters slow steering.

The old IT felt like a Bonneville streamliner in the woods, as though it were designed for high-speed desert use rather than fast trails. The 465 certainly is quicker-steering, but it still is not the ideal woods bike. With a narrower handlebar and plenty of body English you can keep an IT on time between the trees, but you start a tight event at a disadvantage.

Open-terrain enduros are where the IT is really at home. The motocross chassis and the latest aluminum swingarm are ideally suited to high-speed western events. There is not a trace of the frame flex that used to afflict low-tech ITs of the past. Yamaha's new win-at-all-costs approach has made the motocross-based IT the ideal weapon for winning an enduro in a motocross-style special test, rather than simply staying on time in the woods.

Yamaha does help you stay on your minute, though, with some handy little detail touches. For instance, the now-familiar quick-detach rear wheel is even stronger and easier to remove. The axle is now a massive 20mm in diameter, and two spacers have been removed from the securing package, so there are even fewer parts to lose in the mud. And once you get the wheel out, the tire comes off more easily, too. The new DID rims have deeper central wells to let one tire bead ease out of the way while the other is levered off the rim.

Even air-filter servicing is simplified on the new IT. The airbox itself is larger than last year's YZ design, which lets you get the filter in place more easily. Access is made even simpler by a new flip-off airbox cover held in place by a single rubber strap. The design is both basic and, thankfully, waterproof.

The rest of the bike bristles with little, but pertinent, details. You won't need to open up the tool pouch on the rear fender to replace a broken headlamp bulb. The combination light and number plate can be flipped off by hand in seconds, saving you time and possible penalty points at the end of a long enduro.

Yamaha has also mounted the hand guards first seen on the TT250. Unfortunately, these are more ornamental than functional. They do stop some water from hitting your hands, but they offer no protection from branches or rocks, and can even fill with mud in a spill. You may also break the clear plastic top to the new whirlpool throttle if you tumble over.

Apart from these few minor problems, the IT is a very rugged and reliable motorcycle. Team Yamaha's Larry Roeseler proved that point by finishing as top American scorer in last year's ISDT. He rode a bone-stock production prototype of this bike to a Gold Medal in the world's toughest enduro. And while the IT can take you to an enduro gold, it can still be fun for a day's ride in the hills.

RIDE REVIEW

Four-stroke engines? Who needs 'em? Not me. Not when there's an IT465 around. I mean, I know it's a two-stroke, but the IT gives you everything you always wanted in a four-stroke, and less—like that it's not as hard to start, isn't as top-heavy and doesn't have any valves to get out of adjustment. Not only that, the 465 is quicker than a thumper and just about as tractable, plus it's quite a bit easier to handle when you're either creeping along at a walking pace or riding at blindingly fast speeds—which, incidentally, it is capable of reaching in mere seconds. Yet the only four-stroke I've ever been on that would lug down as far and as easily as this tractor-like Yamaha was a prototype Honda trials bike, and it was worth almost $40,000. And was painfully slow, to boot.►