Suzuki Rm250
SUZUKI RM250
CYCLE WORLD TEST
Return Engagement
IT WASN'T TOO LONG AGO THAT LO cal motocross was almost com pletely dominated by Suzuki RMs. Those bright yellow bikes seemed to have th~'rig~ht combina tion of power, suspension and han dling to leave the competition in the dust, week after week. But at the same time, the other manufacturers worked hard to catch and surpass the RMs, while Suzuki seemed content to make only small improvements from year to year. So it didn't take long before the RMs faded into obscurity.
Suzuki attempted a 250-class comeback in 1986 with a partially redesigned RM250; but between a rearsuspension linkage that caused too much friction, along with a slow-revving engine and a poor-performing front fork, the ’86 RM was doomed right from the start.
For ’87, Suzuki has again revised the RM’s rear-suspension design, and has also made major changes to the engine, the brakes and the front fork. But this time around, it all works, making the RM250 one of the most competitive bikes in its class.
Especially nice is the new engine. Gone is the heavy-flywheeled, slowrevving, enduro-style powerband that RM250s have had for the last few years, and in its place is the exact opposite: The ’87 engine is a lightflywheeled, lightning-quick revver with instantaneous throttle response, although the powerband still is very wide.
As a result, the RM250 at last is competitive, acceleration-wise, with the best in the 250 class. The engine pulls hard everywhere, and in fact has the smoothest, most seamless powerband of any 250 MXer on the market. But it’s still not what you would call a “torquer”; the fastest lap times will come if the smooth-shifting gearbox is used to keep the engine cranking in the upper end of its powerband.
Among the bigger changes inside the engine that are responsible for these new power characteristics are: an Automatic Exhaust Control System that now uses a flat-slide valve to alter exhaust-port height according to rpm; a new cylinder with a boroncomposite bore surface; a revised electronic ignition that provides the optimum amount of spark advance at all engine speeds; and a new pipe designed to boost peak power while maintaining a wide powerband.
Really, the only flaw in this hot new engine is the lack of an idlespeed screw on the Mikuni flat-slide carburetor. This can be annoying— and time-consuming—when braking hard into a corner with the throttle closed, because the engine often dies if the clutch is pulled in to downshift. And when the throttle is again turned on to exit the turn, the engine usually comes back to life so explosively that it makes the RM lunge forward too abruptly. The RM250 doesn’t need an idle-speed screw so it could actually be made to idle, but only so the slide could be set so it wouldn’t close off the carburetor bore entirely, which would help keep the engine from dying so easily.
Still, the new engine is first-class, as is the RM’s revised suspension. The KYB cartridge-type fork has adjustable compression and rebound damping, and the rear shock—also by KYB—has a large reservoir and also offers compression and rebound adjustments. But probably the most important suspension improvement for ’87 is in the Full Floater rear end, which has a redesigned linkage that delivers a substantial reduction in friction.
At the very beginning of our test, the suspension worked well, but both ends got progressively less efficient as the test days rolled by. We finally readjusted the compression and rebound damping on the fork and the shock after the third day of riding, and that restored the suspension to its original excellent behavior.
Once dialed-in, the new Full Floater rear end lets the RM250 cross
deep whoops and other MX-track treachery better than any 1987 motocross bike we have tested. There is no harshness over rough terrain at any speed, and the back of the motorcycle never kicks. The KYB fork is very good, too, for it absorbs hard hits well and is responsive in smaller bumps; but the comfort level isn’t quite as good as with the Showa cartridge fork used by Honda. Still, the RM’s suspension works effectively enough to let the tires follow the bumps well, so there is no fear of the bike getting sideways or hopping when entering a rough turn. And there is no headshake, even when both of the disc brakes are used hard.
The RM’s rear disc brake is progressive and grab-free, with a nice
feel that is similar to that of many drum brakes; it even requires about the same amount of foot pressure as a drum brake. The front disc is much stronger on this year’s RM250 than on last year’s due to a change in the brake line material. Like the rear, the front brake is progressive and strong, even though it requires a slightly heavier tug than a Honda or Kawasaki front disc.
There is little to complain about once you’re in a turn, as well, for the RM250 has a newfound steering quickness that rivals that of a Honda CR250R. Stability on hard ground or loamy soil is good, but sandy soil causes the rather short-wheelbased RM to be a bit twitchy. But this is nothing to worry about; the RM is simply busier in the sand than a Honda or a Kawasaki would be.
Another trade-off for the RM’s short wheelbase and quick-revving engine is its tendency to be front-end light. Grabbing a handful of throttle, particularly when the engine is in its mid-range, instantly lifts the front wheel off the ground. A rider soon learns to roll the throttle open in turns that offer good traction, rather than snapping it open. This front-end lightness can also work in the rider’s favor, though, when crossing whoops or rough terrain at higher speeds, simply because it makes floating the front tire across the tops of the roughness a fairly easy task.
Not so easy is adjusting the drive chain. Forget about doing it without a 36mm socket, for the large, deeply recessed axle nuts are impossible to reach without one. And the adjustment needs to be done frequently with the stock chain, which is of poor quality. Otherwise, normal maintenance on the RM250 is easy. The new and narrower chrome-moly steel frame features a removable subframe that makes shock removal easy; the large, foam air filter is easily reached after removing the seat; and getting at the sparkplug is a fairly straight shot from the left side of the bike.
But as nice as these features are, the most important aspect of the RM250—or any racebike, for that matter—is its ability to win. And in practically every respect, the ’87 RM250 is a very competitive motocross machine. And it’s that way right out of the box. Forget about having to do the types of costly engine and suspension modifications that were necessary just to get RM250s of recent years in the hunt; this RM250 can win without them. E3
SUZUKI
RM250
$2899
