We owned two of Suzuki's original 4-stroke sport quads, the LT230, and put many enjoyable miles on them. So when we finally got the call to ride the new 4-stroke 2003 Z400, we were very excited. The chosen riding area was the Miami Creek OHV area in Central California. Why not a wide open riding area? Because Suzuki wanted to show off the handling on the new Z400. The Z400 was developed with 4 major objectives in mind - excellent performance, good handling, great convenience, and advanced styling. We think Suzuki did an excellent job of meeting all objectives!

Performance

Suzuki lifted the motor for its new sport quad out of its very popular dual-purpose motorcycle, the DR-Z400S. The motor is a 398cc, 4-stroke, single cylinder, liquid-cooled, DOHC 4-valve engine. The engine characteristics were modified slightly from the motorcycle so that it develops increased torque in the low-to-mid range, yet still maintains excellent power on the top end. This engine features an aluminum alloy cylinder that is plated with SCEM (Suzuki Composite Electrochemical Material). This cylinder is lighter than traditional designs, has better heat transfer, and allows tighter piston-to-cylinder clearance. This cylinder also has internal oil passageways which contribute to weight reduction by making external hoses unnecessary. Suzuki engineers also laid the motor down an extra 10° as compared to the DR-Z400S. Paired with a dry sump lubrication system this allows Suzuki to keep the center of gravity down low.

The motor is angled forward an extra 10° to keep the center of gravity low

Z400 aluminum alloy cylinder

The aluminum cylinder head is very compact and forms a very efficient combustion chamber with a 11.3:1 compression ratio. While this compression ratio seems somewhat high for pump gas our engine experts tell us the compression on this motor can be bumped up even higher on pump gas due to the efficient head and valve design. The Z400 valvetrain is of the shim-under-bucket-tappet design similar to many high-performance motorcycles. This design allows longer intervals between maintenance than other designs. The engine uses an automatic decompression system to aid starting. When the electric starter button is pressed the system automatically opens one exhaust valve to relieve cylinder pressure and allow easy starting. Suzuki saved additional weight by using a forged aluminum piston with short skirts and cutaway sides. It also uses a L-shaped top compression ring that gives the motor better ring-seal at high rpm than conventional rings. Suzuki engineers chose a Mikuni BSR36 for carburetion with a #130 main jet and 22.5 slow jet. For cooling this motor, Suzuki fitted the Z400 with a large radiator and a thermostatically-controlled fan. They carefully positioned the radiator louvers to keep mud out of the radiator cores. We only heard the fan kick in once or twice when we had stopped to an idle. So how does this high tech motor work in a sport quad? The motor has excellent power throughout the powerband and was very useable at all Rpm's. It started easily and felt very strong. We really like the low and mid-range power that this motor produces. It felt significantly stronger than our slightly modified 400EX. We are anxious to put it up against a stock Raptor, as we think the Suzuki Z400 will be close in performance.

Clutch and Transmission

The Quadsport Z400 uses a manual clutch with a 5-speed transmission and a reverse gear. The clutch is a push-rod system with a lightweight aluminum push rod. The clutch has a very nice, light feel to it. The reverse knob looks and is placed very similar to the Raptor. To engage reverse, choose 1st gear while holding the clutch in. Then turn the reverse knob and move the shift lever from 1st into reverse. The gears seemed to be spaced very nicely and worked smoothly.

Electrical

The Quadsport Z400 uses a unique vertically stacked dual multi-reflector headlight system that is integrated in the front fender. This system was taken from Suzuki's Hayabusa 1300 sport bike. Both upper and lower lights are 30W with halogen bulbs. The rear taillight includes both a 5W multi-reflector taillight and a 21W brake light. The front handlebar plastic includes a neutral selection, reverse selection, and coolant temperature light. The Quadsport uses a maintenance-free CDI ignition system. The generator puts out 150W to power all of the electrical accessories.

We like the look of the vertically stacked headlights.

The rear taillight has an integrated brake light.

Chassis

Suzuki has designed the chassis to provide enough rigidity to handle the power of the Z400 yet still provide the proper amount of flex for handling. The chassis is made of high tensile steel and has a removable rear sub-frame. We think the chassis looks a lot like the 250R chassis that is in use in hundreds of race quads around the country. Suzuki has created a total package that weighs in at only 373 lbs dry. This is 2 pounds lighter than the Honda 400EX and 25 pounds lighter than the Yamaha Raptor. The overall length, width and height are similar to the 400EX but the Z400 has a seat height that is 2" lower than the Raptor and even 3/4" lower than the 400EX.

A look at the new frame

Front suspension

Suspension

The front suspension is an independent double wishbone front suspension with Showa-made coil-over, oil-dampened shocks. The spring preload is 5-way adjustable, and both A-arms are steel. Wheel travel is 8.5". This sounds a lot like the 400EX, doesn't it? The rear suspension is comprised of an aluminum box-section swingarm with a tapered rear axle. A Showa-made piggyback-reservoir shock is mounted on a linkage system. This shock is fully preload adjustable, compression damping is also fully adjustable, and rebound damping is 22-way adjustable. Rear wheel travel is 9.1". We think these may be the same shocks used on the 400EX. If they are not an exact match, they must be very close! Now the big question, how well does the chassis and suspension work? Very well. The Z400 felt a lot like a Raptor when we first sat down on it, i.e. the ergonomics of the seat and handlebars. But that is where the similarities to the Raptor ended. The Z400 does not feel tippy like a Raptor does and handles much like a 400EX. It was very easy to get comfortable on the Z400 and power slides were a blast. The Z400 felt very light and nimble. While the front end felt light, it did not feel so light that it wanted to do wheelies at unplanned times like the Raptor often does. While we have not had extended riding time on the new Z400, we are VERY pleased with how the new QuadSport works. Watch out Honda!

New Z400 QuadSport in action.

Just a slight amount of coaxing to bring the front end up

Odds and Ends

Front brakes are dual hydraulic disc and the rear is a single hydraulic disc. The brakes seemed to work smooth and provided all the stopping power that was needed. Suzuki has chosen Dunlop KT331 tires in the front and Dunlop KT335 tires in the back. These are the same tire pattern Yamaha used on the Raptor but at slightly different dimensions. The wheels are lightweight aluminum with a buff-finished surface. The fuel tank measures in at 2.7 gallons including a .7 gallon reserve. This is similar in capacity to the Honda 400EX but a half gallon short of the Yamaha Raptor. We really like the vacuum operated fuel valve that Suzuki uses as it eliminates the need to shut the fuel off manually. Suzuki has used the same T-shaped seat as was found on it's previous QuadRacers. The seat is narrow at the front allowing easy movement on the quad but wider at the rear with plenty of padding. The seat and the shape of the gas tank made the Suzuki very comfortable to ride. We have only found one annoying feature that could easily be resolved - the fuel tank vent hose keeps popping out of its place in the plastic between the handlebars.

Summary

While we have not put a lot of hours on the Z400 Quadsport, we think Suzuki has put together an excellent contender in the SportQuad category. The Z400 has good performance, and with the motor being the same design as the DRZ-400 motorcycle, a whole host of performance goodies should be available in no time at all. The handling is excellent and the suspension is adjustable for the size of the rider. With a MSRP of $5,699 the Z400 is priced equivalent to the Honda 400EX, and almost $800 less than the Yamaha Raptor. The Quadsport Z400 is an easy choice as a BEST BUY!

Check out the photo gallery for even more pictures!

2003 Z400 Specifications

American Suzuki Motor Corporation
3251 E. Imperial Highway
Brea, CA 92822-1100
Telephone (808) 226-7744
www.suzukicycles.com
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