Kawasaki Kdx80
KAWASAKI KDX80
CYCLE WORLD TEST
Not so long ago kid bikes were dangerous little jobs with waterpipe frames, lawnmower engines and 12 in. wheels. The Japanese have changed all that—all of the major Japanese makers offer at least
one, and most of them have several mini bikes designed for kids. The mini market is large enough that different models, some designed for play, others for racing, are now available. Like the big bikes, most of the radically new designs become available on the racing models first, then get used on the play and enduro models the following year.
Kawasaki’s 1982 KDX80 is such a machine. The 1981 KX80 motocrosser came equipped with single shock rear suspension, the off-road play bike 80 had dual rear shocks. For ‘82 the KDX comes standard with most of last year’s motocross magic.
The Uni-Trak frame has large diameter steel tubing with generous gusseting at the steering head and swing arm mounts. Giant tubes are used for the backbone and front downtube. The backbone is shaped much like larger Uni-Traks, starting at the steering head, continuing to a point at the rear of the plastic gas tank then turning to parallel the ground before ending about mid-seat. The front downtube dives straight down then bends back just below the exhaust before ending. Rear downtubes are also heavy duty. They start at the end of the backbone, go down to the lower rear of the engine where they weld to a large cross tube below the footpegs. More of the same size tube ties the downtubes together to form a strong wishbone below the engine. Seat rail tubes parallel the backbone before heading back to the middle of the large rear fender where they form a handy grab handle. Strength and triangulation are added by a cross tube between the front downtube and backbone, and short tubes between the rear downtubes and seat rails.
Shock placement is much the same as larger Uni-Traks. A single shock rides vertically just aft of the engine, bolts to the frame at the bottom, to the front of a rocker at the top. The rocker pivots in frame rails and gussets below the end of the backbone tube. The rear end of the rocker attaches to two beefy tubular struts that connect to the boxed steel swing arm.
The swing arm is gusseted in many places, providing good strength. Like larger Kawasaki Unis the arm is very long, measuring almost 20 in. That’s lots of length for an 80cc. As a comparison, the> little bike’s swing arm is a half inch longer than the one on a Honda XR500R ProLink!
Suspension travel is 6.7 in. fore and aft. Some adjustment is available at both ends but not as much as larger Unis. The rear shock’s damping isn’t adjustable but our mini rockets thought it was right-on and didn’t need damping choices. Spring preload adjustments are made at the bottom of the shock body with a ramp system like single shock systems used to have. Five steps of spring preload are offered. The excellent owners manual that details maintenance and engine overhaul says you should remove the shock to change the preload, a rather laborious job requiring the removal of the seat, side number plates, and air cleaner base. If you’re creative using tools, the preload can be changed without all the removal. Make sure the area below and around the adjuster ramp is clear of dirt and mud first though. We found the stock adjustments were adequate for a large number of different riders ranging in ability from beginner to expert. The variable rate spring provides the necessary progression to smooth small bumps and not bottom on big ones.
The forks are scaled down models of larger leading axle forks. The stanchion tubes are 30mm in diameter, beefy for the size of the machine, and the spring rate and damping choices are right-on. Adjustment is somewhat limited. Changing fork oil weights is the only adjustment possible since air caps aren’t provided. Most riders won’t need them, but it would be nice to have them.
The KDX is propelled by the same powerplant used in the highly competitive KX80 motocrosser. The compact engine produces lots of usable power for its displacement and five transmission speeds let you use it. The bore is slightly bigger than the stroke, the total size measuring 82cc to take advantage of all the legal class limits. A 26mm Mikuni carburetor feeds fuel through a four-petal reed valve and an external flywheel magneto helps control revs. The clutch is strong and primary kick starting is standard. The piston uses two rings so ring replacement intervals shouldn’t be excessive. The cylinder still uses an Electrofusion coating for abore surface.Thus heat is transferred more quickly to the cooling fins but reboring because of wear or mishap isn’t possible. When things get loose or scarred, cylinder replacement is necessary.
Pipe shape and size is almost the same as the KX80 with silencing material added to the inside of the main cones. Additionally, a small silencer is placed at the end of the rear cone and followed by a large spark arrester/silencer with double mounting brackets.
Air is filtered by a large diameter oiled foam filter in a huge airbox. The air inlet is high on the bike and positioned so water and mud don’t easily enter.
Plastic parts on the bike are nicely made and fit well. Small details are taken care of so the owner doesn’t have to. Cables are nicely routed with proper guides and holders where needed. The rear brake pedal and footpegs are cleated, a good plug cap is standard, rubber covers protect the rear suspension struts on the swing arm, levers, grips and throttle are quality items that don’t need replacement, and the bars are the right shape.
Wheel assemblies are almost the same as the motocrossers but look different. The motocrosser’s have black painted hubs, the KDX’s are unpainted. Spokes, brakes and backing plates are the same. Wheel rim sizes are also the same, 14 in. rear, 16 in. front. Rim material is the only difference between the KX and KDX—the motocrosser has aluminum rims, the KDX steel.
The little KDX turned out to be a good working partner for a surprising variety of riders, in both size and experience.
This may begin with the increased suspension travel of the current mini enduros. Six inches of travel is more than we used to get from the full-size bikes not too long ago, and it works out that the seat height of the KDX 80 isn’t all that much lower than dad used to have.
Thus, even the big kids who look too large standing next to the KDX were more in scale when they sat down. The pintsized beginner can straddle the saddle and touch ground with his toes, while big brother and dad can zip around the camp site, the only limit being that grown-up knees limit steering lock.
Junior gets even when it comes time to start the engine. The 80 fires quickly, but the kick lever is short and it’s forward. Big boots don’t fit well and long legs must kick backward rather than down. Awkward, in—sorry—short, but easy when the rider is short.
The choke is tucked away on the left side of the carb, easy to reach and needed when the engine is cold. We learned, at the cost of a few plugs, to push the choke off as soon as the engine fired. If you don’t, the plug fouls in seconds.
The KDX80 is a friendly bike, almost a neighborhood bike. Not only will it start with one kick and idle in a civilized manner, it’s quiet, which makes friends in the woods and around camp and even next door when dad just has to make sure the engine is running right.
The 1981 KX80, the real racer, was fast and powerful and a bit much for play riding. The KDX has the same basic engine slightly tamed and muffled. But Kawasaki has somehow managed to keep the power > of the motocrosser while improving lowend and power delivery.
KAWASAKI
KDX80
$719
SPECIFICATIONS
Thus the KDX does start easily and it will idle, while the neighborhood test panel, i.e. the various kids of the proper size who took turns wringing out the KDX, found it to have enough power even for them.
After some practice. The mildly detuned engine will off idle without sputtering or balking but the power band isn’t as wide as the one on, say, a Honda XR80.
The KDX pulls at low revs, but not terribly hard and the four-stroke kids were a bit disappointed at first. Once persuaded to wind until the engine screamed and to stay one gear lower than they were used to, they found the KDX to be a bunch faster than they expected.
Some informal drag races proved the KDX to be faster than we expected. It would stay right with the KX80, and even turned equal time on the motocross track. Same frame, wheel travel and suspension after all and nearly the same peak horsepower.
For riders who do more than race their minis, the KDX is a better choice than the KX80. The quiet exhaust doesn't offend neighbors, the spark arrester makes it legal in forests and the rear frame loop and flat fender makes a convenient area to lash a jacket or a tool kit.
At last the gap has been bridged between the full-bore mini motocrossers and the XR80. It’s taken a while to get the performance of the motocrossers in a civilized and rideable machine, but Kawasaki hasn’t wasted the time. 83
