Kawasaki Kx125
KAWASAKI KX125
CYCLE WORLD TEST
ENOUGH TO MAKE THOSE RED AND YELLOW 125s GREEN WITH ENVY.
For the past couple of years, Kawasaki’s KX125 has been the bridesmaid of 125 motocross. The KX has been a really good, competent machine, but not quite good enough or competent enough to whip Honda’s CR 125R, which has been just a bit better.
Has been.
But no more.
no more. This year’s KX 1 25, you see, is going to turn the tables on Honda. The ’84 KX might not look radically different compared with last year’s bike, but mechanically it’s quite a bit improved. And on the track, the only place where any of this really counts, the new KX125 is significantly different, mostly in that it no longer has to settle for finishing behind the CR Hondas. This time, Kawasaki got it right.
One of the first things a rider of an ’83 KX125 will notice about the ’84 is the way the bike fits. KX125s over the past few years have had a decidedly cramped feel, especially for anyone bigger than about 5-foot-7; but no one who rode our '84 test bike, including some 6-footers, complained about the seating position. Physically, the new' bike isn’t any bigger, but it has a redesigned frame, seat and gas tank that spread out everything the rider comes in contact with.
That new frame bears little resemblance to the old one in design as well as in dimension. The steering head angle is slightly steeper (27.5 degrees compared with 28 degrees on the ’83), and the usual rear downtubes that angle forward between the swingarm pivot and the backbone are gone. This is similar to the frame design found on the latest RM 125/250 Suzukis (although they still have a rear downtube on one side), and the KX uses it for the same reason: to make room in the cluttered area behind the engine for a single airbox that is big enough to house a large filter element but that won’t get in the rider’s way. The lack of triangulation caused by the elimination of those downtubes required the use of larger-diameter tubing and increased gusseting in many stressed areas, especially around the swingarm pivot and the steering head.
Cradled amongst those relocated frame tubes is a new engine. Actually, it’s not entirely new, for the basic design is the same as before; but the ’84 engine incorporates a number of significant changes that improve its performance. For one thing, both crankshaft flywheels have been drilled with two 25mm holes to reduce flywheel inertia for quicker revving; and those holes have been plugged with aluminum to maintain the crankcase's compression ratio, which is an important factor in the transfer of fuel from the crankcase to the combustion chamber.
The engine’s bore and stroke are unchanged at 50mm and 50.6mm, respectively, and the cylinder still is of the Electrofusion design (Kawasaki’s patented process of electrically covering the aluminum bore surface with a hard, .007-inch-thick molybdenum/steel coating), but the state of tune is different. The exhaust port is higher, all of the other ports are wider, and the exhaust system has more volume in its center section. There’s also a new capacitive-discharge ignition with slightly less spark advance. A reed valve with six carbonfiber petals controls the intake breathing, with fuel supplied by a 34mm Mikuni carburetor that uses an unusual flat-bottom slide. This “R-slide” is designed to allow cleaner, crisper running at smaller throttle openings.
Most other areas of the engine have been somehow redesigned as well. The main engine cases are stronger and have wider mating surfaces to provide a better seal. The clutch friction plates have radially grooved surfaces for better oil drainage. The six-speed transmission uses the same ratios as last year’s engine, but many of the individual gears either have an improved heat-treatment, wider teeth or are made of a stronger material.
What’s surprising, however, is that all of the KX125’s tuning modifications combine to increase the claimed horsepower output only by the smallest of margins (32.8 hp at 11,000 rpm, as opposed to 32.5 at the same engine speed on the ’83 KX). But increasing peak horsepower wasn’t the factory’s objective; increasing peak torque, as well as lowering that peak in the rpm range, was. The new motor pumps out a claimed 20.98 lb.-ft. of torque at 9500 rpm compared with 15.77 lb.-ft. at 10,500 on the ’83 engine. That’s a 33-percent increase in torque, which is impressive in itself; but the fact that the increase comes at a 10-percent lower rpm is almost unbelievable.
You become a believer, though, once you ride the KX125. This engine breaks all the rules concerning 125cc motocross bikes. Normally, a 125-class engine can be tuned to deliver strong low-end or healthy mid-range or potent top-end, but not all three. But the KX125 does just that. And what’s most amazing is that the KX pulls that trick off without any exhaust-control devices like those used on Honda’s or Yamaha’s 125 MX bikes.
At the racetrack, the KX125’s engine, superiority is instantly made clear. It pulls well from way, way down low in the rpm range and continues to accelerate hard up past the point where most 125s sign off. As a result, the KX is the undisputed king of the start straights, it lunges out of all kinds of corners—fast or slow more quickly than anything else in the class, and it powers up hills so fast that you swear you’re on a 250. That broad powerband is a real advantage, too, that allows a rider to concentrate on the track instead of on engine rpm. And should the engine somehow fall out of the fat part of the powerband, one quick fan of the clutch lever will bring the revs back into the all-business zone.
No wonder, then, that everybody who rode our KX125 test bike—including a few riders who normally dislike 125s because of the effort required to keep an eighth-liter engine in its powerband thought the Kawasaki was enough fun to be illegal. They weren’t as enthusiastic about the design of the aluminum kickstarter, though. The kick lever spins the engine easily enough, but it generally causes the top of the operator’s instep to bash into the rear of the footpeg at the bottom of the kick stroke. We soon learned that the painless solution is simply to position your foot fairly far forward on the kick pedal before kicking, which allows your boot sole to hit the top of the peg at the bottom of the stroke.
No such problems were encountered with the KX125’s suspension, which is almost as wonderful as the engine. Almost. The KYB front fork has 11.8 inches of travel, 43mm stanchion tubes and a compression-damping blow-off valve in each fork leg. The blow-offs are adjustable to any one of eight detented positions by turning a small screw in the bottom end of each fork slider. We found that the fork transmitted a lot of midstroke shock to the rider’s arms when adjusted to the standard setting (fourthstiffest position); so we backed the screws out to the full-soft setting, which helped but didn’t eliminate the problem altogether. On smaller or rolling-type bumps the fork action is quite good, so the rider usually doesn’t feel any harshness until he either lands from a big jump or brakes hard going into a choppy, downhill turn.
On the other hand, just about any kind of bump is handled nicely by the rear suspension. The new KX has yet another version of Kawasaki's Uni-Trak singleshock setup, this time with a new, aluminum-bodied KYB shock, a box-section aluminum swingarm, and a revised linkage that gives slightly less-progressive rear-wheel rates than in ’83. The aluminum link between the swingarm and the steel rocker arm above the shock now has grease fittings, making that part of the linkage easier to service, but the rc itself and the swingarm pivot still re. e disassembly to be regreased.
This year, the shock’s remote reservv r uses a bladder rather than a deCarbo, ■ style piston to separate the pressuriz c-^ nitrogen from the damping oil. A blad der, Kawasaki explains, can react mrt quickly to small impacts than can an O ring-sealed piston, and a bladder also doesn’t rub on the reservoir’s inner waifs and produce heat. A four-position com pression-damping adjuster knob is lo — cated on the bottom of the reserve i where it’s easy to reach. Not so the foi r position rebound-damping adjuster av, the shock body, which is hidden unde rubber cover behind a frame tube am * water-splash guard, all of which is T hind the right sidepanel. It's kind o . pain to get at, especially when the t < haust system is hot, but at least it doe: ’ need adjusting often. Likewise, adjus a> the shock’s spring preload is, as alw,4 $ difficult on the KX125, but this yea frame design makes the job a bit easier The owner’s manual says that the shoe! has to be removed to turn up the preload but it doesn't; a long punch and a ham mer will do the job with the shock stil bolted in the chassis.
Thankfully, the rear suspension wo ^ so well that adjustments shouldn’t \ frequent necessity. The rear tire fc the ground almost perfectly, and st bumps and ripples seem to disapp#1 they pass beneath the rear wheel, earth-shaking landings from skv jumps don't jar the rider at all. Long motos made the shock reservoir on i test bike too hot to touch, but nol 1^, ever noticed any damping fade. And c ing flat-out through whooped or shi p lipped sections of track almost neve* causes the back end to kick or side-hop.
You can also run the KX125 int< ; turn about as deeply as anything rm ‘e thanks to brakes that are progress, f predictable and, above all, strong. 1 * front disc brake is a real powerhou: t able to generate enough stopping force t* lift the rear wheel completely off f i ground if the rider wishes—and if ’ not careful, even if he doesn’t w i There’s not much to complain about an cerning the rest of the KX’s wheels, ei ther, although the straight-pull spoke did insist on loosening until they becam fully seated. Dunlop K790 motocrcs tires are standard equipment, and tb : drew mixed reviews from our test rid s The tires work well on loam and d t soil but skate around on hardpack. 1 so, the KX can be ridden aggressively )i hard terrain without getting completel out of control.
Elsewhere on the KX, small but i aportant items have been well the tout. The hand levers are a little ithis year to give a more positive feel, handlebar has a bend that seems se most riders. The grips have an ag^sive pattern but are very soft, ore's an easily removed, bolt-on kickand. The air inlet is under the seat here water can't enter easily, and the >am filter element is quickly accessible y removing the airbox sidecover. All is )t perfect in the air-cleaner départaient, though, because the airbox cover doesn't fit tightly and lets in water, dust Vnd even small objects. The first time we leaned the filter (just after washing the ike), in fact, we found the drain hole ugged with small pebbles and the rbox half-full of water.
And that wasn't the only problem suf"ed by our test bike. Our KX125 had sufficient clearance between the swingarm and the frame rail just above the swingarm-pivot bolt. Consequently, on full compression the front of the arm would hit the frame rail. And the chain often fouled the frame in this same approximate area. Not only that, our bike broke its front exhaust-pipe hanger during only its fourth ride.
At least our KX125 didn't do what some others have done: break the frame just in front of the footpeg gussets. We’ve seen a few such occurrences, and even Kawasaki admits to the problem on some earlier KX125s ridden on stadiumstyle courses by pro-level riders. The company claims that later-model ’84 frames have been modified to prevent this problem, and that Kawasaki dealers have been issued gusset kits to be used in the repair of any '84 KX125 that has broken its frame.
A broken frame is nothing to sneeze at, for it’s a problem that is annoying at best and expensive at worst. But despite the few problems the KX1 25 might have, it’s still better than any other production 125 motocrosser at one very important thing: winning races. This is the quickest and surest way to a 125-class checkered flag that you can roll out of a showroom in 1984. Which doesn’t mean that simply riding one guarantees that you’re automatically going to win; it means that whoever does end up in victory circle probably will have gotten there on a green bike . . .just like yours. |o]
KAWASAKI
KX125
$1799
