The Motorbike Archives

So what, you may say. Playbikes are intended for fun, not serious competition. Well, what's fun about pushing your bike up a loose, rocky uphill because the engine doesn't crank out enough power to pull you up? And what's fun about getting tossed on your ear because your bike doesn't handle well? Beginning riders in particular need all the help they can get from their machines. To survive in the sport long enough to graduate to a "serious" off-road bike, a budding dirt rider needs to begin his riding career with a good off-road mount.

Apparently Suzuki agrees: their brand-new DR250Z is a product of a serious effort to produce a better-than-average playbike, and that's good news for advanced as well as non-expert off-road riders. The factory injected Suzuki's latest technology into the DR250 chassis and engine: among other things, the powerplant carries Suzuki's Twin Swirl Combustion Chamber (TSCC) cylinder head, and the running gear features the Full Floater rear suspension system. As a result, the new mid-sized four-banger works notably well for a first-year effort.

The DR engine displaces an actual 249cc by means of a 72.0mm bore and a 61.2mm stroke; the short-stroke Honda XR250, in comparison, measures 74.0mm by 57.8mm. Like most of Suzuki's newly designed four-stroke engines, the DR250 powerplant is centered around the TSCC cylinder head. The patented TSCC head's four-valve design improves intake charging efficiency compared to a two-poppet setup, while the combustion chamber shape promotes a swirling action claimed to improve throttle response, increase power, and provide cleaner combustion through improved fuel-mixture burning efficiency. The 26mm intake valves and 22mm exhaust valves are set at a fairly narrow included valve angle, which helps smooth intake tract flow, and the piston has a flat-topped dome with modest valve-pocket cutouts.

Playbike and semi-serious off-road riders will welcome the DR250 for its above-average suspension and relatively light weight. But those riders searching for big horsepower output will have to look elsewhere.

Since it actuates the four valves through forked rocker arms, the single overhead camshaft has only two cam lobes. The rockers feature screw-type adjusters which let home mechanics tinker with valve adjustment. Access, though, is tight: the front downtube crowds the exhaust-side adjusters, and you must remove the fuel tank to get to the intake-side adjusters. A durable Hy-Vo-type chain drives the camshaft, and an automatic chain tensioner eliminates maintenance worries.

Feeding the engine is a 28mm Mikuni slide-type carburetor. It takes minimal effort to reach the oiled foam air filter element for servicing, which makes this messy but necessary chore a little less odious. The exhaust gases exit through individual head pipes which are upswept and join an effective muffler /spark arrestor approved for use in National Forests.

A gear-driven counterbalancing system, in an unusual location, combats excessive vibration in the 250 thumper. The balancer shaft is situated above and behind the crankshaft axis (which is not unusual), but the entire balancer, drive gear and driven gear are all located within the center cases. Most balancer-equipped engines house the drive gears in one of the side cases. The DR250's setup, in contrast, is particularly narrow and tidy. The drive gear sits immediately to the right of the right-side flywheel, and the balancer weight rotates between the two crank flywheels. The balancer driven gear has six damper springs that ease shock loads in the balancer system.

The ignition rotor spins on the left end of the crankshaft; the cam drive and primary drive gears are located on the right end. The DR uses helical-cut primary gears (much quieter than straight-cut gears, albeit slightly less efficient). Power passes through a multiplate wet clutch to the five-speed transmission, and from there to the rear wheel via a 520 final-drive chain.

A manually operated engine de-compressor eases the 250's starting drill, though this system is less convenient than Honda's and Yamaha's automatic, kickstarter-activated compression-release systems. The Suzuki owner's manual divides the starting procedure into three steps. First, squeeze the handlebar-mounted lever. This activates the decompression mechanism, which cracks the exhaust valves open just enough to let the engine pass top dead center easily. Next, slowly stroke the kickstart lever through until the decompressor lever returns to the "home" position. The piston is now past TDC. Finally, give a stout full-stroke kick to the start lever to light the engine off. If the decompression lever can be pulled in with no resistance and returns to the home position when released, the piston is past TDC and need not be eased over. Just kick away.

We used the starter decompressor primarily when the engine was cold; the DR takes up to six kicks to light off when cold but starts readily with or without the decompressor after the engine has warmed. After a moderate warm-up period, the 250 carburets cleanly, and the throttle response is free of glitches or hesitations. A useful amount of torque covers a wide range of engine speeds; the 250 will lug way down low and still rev out willingly, although the engine feels flat on the top end. Overall, the 250 engine has a friendly nature; the wide power spread and abundant flywheel effect make the DR extremely tractable and easy to ride. The 250 shines on loose uphills or tight, snotty trails; the bike keeps plonking forward, demanding little from the rider.

"Extremely tractable" doesn't mean that the DR250 is a horsepower demon. Quite to the contrary, its peak output of 16.76 horsepower puts it squarely at the back of the pack in the 250 four-stroke class, and on par with the Honda XR200R. Two-stroke enduro and MX 250s regularly pump out 30 to 35 ponies, which really puts things into perspective.

In some situations 17 horses simply aren't enough. For example, it can be difficult to keep the front end light over a long set of whoops, and on wide-open desert trails and fast fireroads the DR feels strained. While 250 four-strokes in general suffer a dearth of horsepower, the DR's lack of power is especially acute; playbike-type riders may not object, but more serious off-road competitors will be tempted to explore other options.

Although the Suzuki's five gearbox ratios match the engine characteristics nicely, the DR doesn't shift well with or without the clutch. Shift action is balky and we missed more than a few gear changes. The clutch fades with heavy use, and doesn't disengage cleanly when hot, even when readjusted.

Granted, the fat powerband obviates clutchwork some of the time, but for real tight, rough work the clutch just isn't up to snuff.

Thanks to an up-to-date chassis, the Suzuki handles better than the average playbike. Although the DR's Full Floater rear suspension system differs slightly from the Full Floaters found on the RM-series motocrossers, the design and basic layout remain unchanged. Suzuki changed the lengths of various linkage pieces, the materials, and the location of some of the pivot points to accommodate the play-bike's decreased travel. For example, Suzuki replaced the aluminum upper rocker found on the MX bikes with the DR's steel rocker. The shock, however, is still compressed at both ends, the swing arm is a box-section, RM-like aluminum item, and the linkage provides a rising-rate effect.

The aluminum-bodied shock itself is nitrogen-charged, and it has a remote reservoir and four-way adjustable rebound damping—all features carried over from the RM dampers. Naturally, Suzuki altered the shock valving to suit the DR's weight, suspension travel, and projected use. As with the motocrossers, you can replace the DR's shock oil when it begins to break down. Also, like the motocrossers, the DR's shock spring uses threaded adjusters for preload adjustment; the dual-purpose SP250 features a ramped collar with only seven possible settings. The DR provides 9.5 inches of rear-wheel travel—plenty by playbike standards.

The 250's fork is derived from past RM-series bikes; the fork tubes are 36mm in diameter, in contrast to the 38-42mm fork tubes used by most competition bikes. The springing and damping rates are unique to the DR, and the fork provides 9.6 inches of well-damped front-wheel travel. Separate air caps come as standard equipment on the 250. Suzuki, though, recommends running the bike with zero psi in the fork. We liked the DR with nine pounds of air up front and the shock damper on the number three position.

Riding the DR250 causes something of a revelation. Although the 261-pound Suzuki can't be called a featherweight, it is light compared with the Honda 250 thumper, which weighs about 20 pounds more. For the record, two-stroke MX bikes run from about 230 to 240 pounds with one gallon of gas, and Yamaha's two-stroke 11250 enduro bike weighs about 245 pounds. The DR feels tight and compact, if not light, and it's comfortable to ride sitting down or standing up. The lowish 35.5-inch seat height puts the novice at ease, but the DR still has a useful 13.2 inches of ground clearance available and footpegs a relatively safe 14.5 inches off the ground.

The DR steers precisely, and you're free to choose the tight inside line or slide around the outside; the front end sticks nicely and resists pushing the front wheel. Considering its modest 55.9-inch wheelbase, the 250 works remarkably well in sand and it keeps tracking dead ahead through deep whoops; although the rear end kicks out a few inches to either side, the bike never side-hops alarmingly. Off jumps, however, the rear end bottoms too easily and we felt a noticeable amount of fork flex. A slightly heavier shock spring or more progressive shock action and the full-on 38mm Suzuki fork would be welcome additions.

The 250cc powerplant can withstand frequent water crossings, but the brakes fare less well. Both ends take quite a while to come back after a thorough soaking, and neither works especially well even under the best conditions: the front brake feels spongy and needs more stopping power; the rear brake is overly sensitive.►