Suzuki Rm-Z250
CYCLE WORLD TEST
SUZUKI RM-Z250
THE LITES ARE ON!
RYAN DUDEK
INHERITANCES ARE FANTASTIC. JUST ASK PARIS Hilton. This, too, is the case for Suzuki's completely redesigned RM-Z250, the rightful heir to the development concept of the championship winning RM-Z450. Suzuki took what it learned from winning races with Ricky Carmichael aboard the RM-Z450 and directed the technologies into the all-new RM-Z250 with hopes of making a serious Lites-class contender.
This is Suzuki's first purebred 250cc four-stroke motocrosser; the previous model was a leftover from the Suzuki/Kawasaki alliance. But that's all ancient history, and the new 250 was 100 percent designed and developed by Suzuki. The finished product is a beneficiary I actually got to ride.
The heart of the bike is an exceptionally com pact, 249cc, four-stroke, dohc, four-valve engine. Its compactness was achieved through a semi-dry sump lubrication system featuring separate oil chambers for the transmission and crankshaft. The transmission is used as the oil sump, allowing low crankshaft placement while reducing engine height. So not only can the engine be remarkably small, it can be placed low in the chassis for a more favor able center of gravity.
Up where the power is generated, the aluminum cylinder bore is electro-plated with a nickel-phos phorus-silicon-carbide coating that improves dura bility and allows faster heat transfer. The head con sists of titanium valves opened by hollow camshafts machined from forged-steel billet. Fuel arrives via a Keihin FCR37 carburetor with throttle-position sensor and accelerator pump. The ignition system has two maps that automatically increase idle speed on trailing throttle to reduce engine braking entering turns. Rev limits are set for optimum high-rpm and over-rev performance.
On the track, the engine feels strong for a Lites class bike. Power characteristics are much like those on the Kawasaki KX25OF: lots of torque making a meaty low-to-mid-range powerband. That type of power is good for riders who shift too early, not using all the power in the revs. If you don't shift early and tend to rev the bike, that's okay, too. Rev limit is 13,200 and the engine gets up there fast with a fiery drive. The motor really offers the best of both worlds. If you're a revver or a short-shifter, the 250 copes with both styles admirably, able to accelerate out of corners smooth and fast, boosting you to the next bend in a blink of an eye.
SUZUKI RM-Z250
$5999
American Suzuki Motor Corp.
www.suzukicycles.com
When it came to changing gears, Suzuki chose to use a new link-type shifting mechanism, switching from the gear-type used on the previous model. The new mechanism is said to improve shift feel and precision. But if improving shift feel means making it hard to shift, Suzuki succeeded, because the RM-Z is one of the stiffest-shifting modern bikes I have ever ridden, even more so under power and high in the rpm range. But at least I never hit neutral, even while pulling into the pits. In fact, I actually had to handshift the lever into the neutral position. No fun, especially after a stall; the RM-Z didn't like to re-start in gear, so the neutral thing became a nuisance.
Not surprisingly, the 250 chassis was directly inspired by the 450 and uses a very similar aluminum twin-spar frame Suzuki says is nearly 2.5 pounds lighter than the previous steel frame. The swingarm has the same shape as the 450's with a cast-aluminum front section and extruded main arms.
As for suspension, Suzuki merely equipped the 250 with the same pieces used on the 450. The fork is a Showa 47mm cartridge-style unit with 22-way compression damping and 20-way rebound damping. I turned in the compression one click from the stock setting (7 to 6) to help steering stability.
Still, the fork was a little soft on the initial hit, which is good for small bumps but allowed the front end to dive going into some corners.
Out back, Suzuki's linkage system places the suspension load on the swingarm instead of the frame, enabling a lighter frame. This also allows smoother movement of the shock and linkage for improved rear-wheel traction. The Showa shock uses a 50mm piston and an 18mm inner rod. To make the rear work optimally, we slowed the rebound down by one click from stock (7 to 6), turned in the low-speed compres sion 2 clicks (8 to 6) and changed the high-speed from the stock setting (1 turn out) to 11/4 turns out.
Though it uses basically a 450 chassis, the 250 handles even better than the agile 450. Credit the lighter weight and more refined frame. The 250 is a stable ride on every part of the track, allowing the rider to do less work keeping the bike in line at high as well as low speeds and in bumpy or smooth sections. Plus, the 250 turns exceptionally well in ruts, tight 1 80s and even sweepers.
On the comfort side, ergos were perfect for my fellow testers and me-5-foot-6 to 6-foot. Larger radiators are unnoticeable under the sleek and stylish shrouds. Specially designed seat cover and foam material offer better grip and high comfort, though one tester wanted even more traction on the seat. Renthal tapered-aluminum handlebars are stock, so there is no need to upgrade like in the past when steel bars were standard. Same goes with the on-the-fly clutch lever adjuster on the lever perch, another stock goodie.
All in all, this new RM-Z250 is capable of winning, but we had expected it to be nothing less. Of course, without rounding up the others, we can't say if this is the best 250 four-stroke, but it is sure going to be close.
