Suzuki Dr350
SUZUKI DR350
RETURN OF THE MINI-THUMPER
IT'S ALMOST UNANIMOUS AMONG dirtbike riders: A 350cc four-stroke is a good thing. Unfortunately, in recent years, that kind of dirtbike hasn't been a saleable thing. Suzuki, with its 1990 DR, thinks it has the cure.
But so did Honda in 1983 when it introduced the XR350, still held by some as the best Honda off-road four-stroke. It didn't sell well, though, and was pulled from the lineup after two years. Yamaha was next to step up to the plate, but its 1986 TT350—while a hit with a limited number of riders—went down swinging after two years of so-so sales. Why should Suzuki succeed where others have failed?
The American branch of the company, w hich provided the impetus for the DR, reasoned that the XR and TT 350s didn't catch on due to faulty execution. The concept of a middleweight Thumper trailbike was still sound; the advantages of such a bike over a two-stroke being better mileage, freedom from having to mix oil with gas. increased engine durability and —to some—a better-sounding exhaust note. And compared to a big-bore four-stroke, a 350 could be lighter, much more agile and tons easier to kickstart.
What tripped up the DR's predecessors. believed U.S. Suzuki personnel, was that the motorcycles weren't perceived as “serious” enough by America’s enduro and playbike riders. Those after performance purchased 250cc motocross bikes, and those who were Thumper fans went for all the gusto they could stand, and signed up for the big 600s, leaving the 350s in a void.
To sway those riders, Suzuki believed it had to give the DR350 as much engine and suspension performance as it could while keeping its price tag within reason. After a technical presentation and a brief riding session at the bike's recent press introduction. we can say that Suzuki has apparently met those goals.
Making the bike as light as possible was a prime consideration, as that not only makes life easier for the powerplant and suspension components, but for the rider, as well. If the DR’s claimed dry weight of 249 pounds turns out to be true, it could be as much as 15 pounds lighter than the 350s that came before. Part of the weight savings comes from the bike's mild-steel frame, whose backbone holds engine oil. so a separate oil tank isn't needed.
The dry-sump engine itself has been made as compact as practical, and uses SACS (Suzuki Advanced Cooling System) technology as pioneered on the GSX-R streetbike series. The DR motor doesn't use a separate radiator to cool its oil as do the GSX-Rs, but it does employ the system's strategically placed oil-jets to quench interior hot spots. Otherwise, the engine is fairly conventional, using a four-valve cylinder head and a single, chain-driven overhead camshaft. Bore and stroke work out to 79x71.2mm; redline is set at 9000 rpm; carburetion is via a singlethroat. 33mm Mikuni; the transmission has six speeds.
Front suspension is provided by a conventional, multi-adjustable fork, a 43mm Showa cartridge-type as used on motocrossers before upside-down units became the rage. Rear-suspension tasks are handled by a single Showa shock with remote oil reservoir, and adjustments for rebound damping and compression damping. Suspension travel at both ends is a claimed 11 inches.
NEW FOR 1990
By far the most-interesting component of the DR350 (and its smaller brother the DR250, identical .-»ave for bore-and-stroke dimensions, and weighing 3 pounds less) is the bike’s swingarm. Made of aluminum, the three-piece unit —two forged side arms and a cast center section —is glued rather than welded together. This is a first for a motorcycle, although the aerospace industry has been using a similar heat-cured bonding technique for years. Suzuki claims the advantages are a more-precisely aligned swingarm assembly and reduced production costs.
Our riding time on pre-production DRs was limited to a few hours on a makeshift motocross track; not the ideal venue for a trailbike, but we did come away with some favorable assessments of the bike. It starts willingly, aided by a compression release, and power is available across a broad powerband. The DR won't pull out stumps like a good 600 will, but neither is it anemic down low. Straightline acceleration doesn't feel as brisk as a 250cc two-stroke, but you could run the DR in a national enduro or ISDE qualifier (which Suzuki plans to do) and not be embarrassed.
We’ll withhold final judgment on the suspension until we can get a production DR on our home trails, but we can say that the pre-production bike felt as well-suspended as motocrossers of a couple of years ago, which is to say pretty darn good, if not exactly state of the art.
But, without a doubt, this is a far better machine than either the XR350 or TT350, suggesting that for 350cc, four-stroke dirtbikes, at least, the third time may indeed be the charm. El
