Kawasaki 750 Mach Iv
KAWASAKI 750 MACH IV
PREVIEW
How Does It Handle, How Does It Go? We Rode Kawasaki's New Big-Bore Three And Found Out!
DAN HUNT
KAWASAKI UNVEILED a new "super-sickle" at a bubbling, wobbling press preview inside and outside the Queen Mary, formerly of Liverpool, now of Long Beach. Both the 750-cc Mach IV and the Queen Mary survived intact.
While everyone was betting that Kawasaki would go to a four-stroke when they decided to upstage the former leader of the line, the 500-cc Mach III, it didn't work out that way. Kawasaki has a good thing going with the 500-cc and 350-cc three-cylinder machines, and they have three years of experience with the basic design. So the Mach IV is, quite literally, more of the same.
The engine is completely scaled up in size, rather than incorporating any components from the Mach III. Crankshaft,
cases, gear sizes, cylinder and head castings are all larger to handle a claimed output of 74 bhp!
Like the 500 and 350, the 750's intake, transfer and exhaust openings are controlled by the conventional pistonport method—the most obvious solution to designing a reasonably narrow three-in-line two-stroke engine. Hand in hand with this layout goes a crankshaft with throws 120 degrees apart, offering perfect primary balance. As the crankshaft gets rather long in such a design, it is supported by six ball-type main bearings to minimize flexing along its axis.
In brief blasts up to 95 mph, we found that the 750 exhibited little in the way of disturbing vibration in spite of its large dimensions, even less vibration than that produced by the smaller Mach III.
The increased smoothness is no doubt due to the fact that the Mach IV is in a milder state of tune than is the Mach III. Maximum horsepower occurs at a leisurely 6800 rpm, compared to the 500's peak of 60 bhp at 7500 rpm. The 750 pulls high gear fairly well from 3000 rpm and really begins to operate at 4000 rpm. So while the 750 is definitely a performance machine in conception, it will lend itself quite well to leisurely two-up touring, assuming that you can handle the fuel bill, which is bound to be high.
As far as weight and girth go, the 750 seems barely bigger or heavier than the Mach III. The actual difference is 40 lb., so the 750 tips the scales at about 450 lb. with its 4.5-gal. fuel tank half full. This is about 25 lb. more than a Triumph 650, or 50 lb. less than a Honda 750. The only 750 on the market weighing less is the Norton Commando, at 426 lb. with half a tank of gasoline. While Suzuki's shortly forthcoming 750 is also a three-cylinder two-stroke, it is water-cooled and probably weighs more.
The Mach IV's 55.5-in. wheelbase makes it fairly easy to > maneuver in tight going. To get the frame as low as possible and yet provide a comfortable fit for the engine, the 750's bore/stroke ratio (70 by 62mm) is more markedly oversquare than the 500's (60 by 58.8mm). A person of average height can easily sit with both feet on the ground, although shorties will have to stretch some.
KAWASAKI 750 MACH IV
Frame configuration of the 750 follows that of the other Threes. It has a double cradle and double top rails emanating from the steering head. An extra bracing tube from the steering head is secured to the top rails by a crosstube just above the cylinder head. Triangulating struts connect the swinging arm pivot area to the top rails at roughly midway point, serving to resist both longitudinal frame flex and off-center torsion produced by the powerful engine.
Handling is about akin to the 500, stable and smooth in a straight line at high speed, with a moderately stiff ride. For some reason, the 750 shows the same reluctance as the 500 to be pitched into a turn, and tends to straighten up on you unless you consciously hold it there. The rear shock absorbers provide rather dismal damping and allow the Mach IV to wiggle should there be any bumps or rises in mid-turn. The conclusion here is that, if you want a Kawasaki Three that handles impeccably, you'd better stick to the righteously nimble, well-balanced 350. Getting the 750 right will involve fiddling with the shock absorbers and front/rear spring rates.
The 750 has an excellent single-disc, hydraulically-operated front brake, working in combination with the usual drum-type rear brake. The new front, using a stainless steel disc, provides enough stopping force to skid the front tire at any speed, and delivers excellent feedback through the system to the braking hand. The rear brake is adequate, if somewhat insensitive. Together, they are more than a match for the weight and potential speed of this motorcycle. Fortunately, the new 500 Three also gets the disc-brake treatment up front, where the old standard drum proved to be less than powerful and/or fade-free.
As expected, the Mach IV is an absolute jet, leaves all sorts of rubber on the pavement, pulls strongly in every gear, and shows absolutely no lag as you click your way from first to fifth. First gear seems a trifle high for slow going until you accustom yourself to how slowly the engine can turn.
Until we subject the machine to a full road test, we can only speculate on the actual figures this machine will produce at a drag strip. But doing some quick figuring with power-toweight ratios, we find that the 750, with a 150-lb. rider aboard, yields a Ib./bhp figure of 8.1, compared to 9.0 for the 500, or 9.7 for a Honda 750.
Assuming that Kawasaki's claimed bhp figure is reasonably valid, or at least in line with the figures they claim for the 500, we can predict that the Mach IV will slash its way through the quarter-mile in the low 12-sec. bracket with a trap speed of from 105 to 108 mph. Top speed will be in the neighborhood of 125 to 130 mph, with proper gearing.
We aren't giving out prizes yet, but our guess is that the Mach IV will be the quickest and fastest thing you can buy with lights and mufflers in the 1972 model year. It also seems likely that Kawasaki will take advantage of the AMA's 750-cc displacement limit. An "R" version of this engine in a road racing frame would be formidable on the Superbowls!
List price of the Mach IV has not yet been announced, and the 10 percent surcharge on imported machines has thrown the price makers into temporary turmoil. But, as Kawasaki's pricing policy seeks about a S200 spread between their Threes, chances are the 750 will be priced from between $1200 and $1300. [Ö]
