Kawasaki's 750-Cc H2-R Road Racer
ABOUT FOUR GOOD hard steps, pop out the clutch with about one-quarter throttle, and there is a deep-throated gurgle as the rear end slides sideways slightly and the 100horsepower engine comes to life. Back in with the clutch, climb aboard as the revs go up to about five thou, and very gently feed back in the clutch, as the rump involuntarily pushes hard on the large seat back.
The machine is Kawasaki’s racing version of the new H2 street machine. I spent a day riding the racer in Japan. It completely squashes the theory put forth by some proponents of the AMA 750 ruling on displacement that the big-bore two-strokes would be handicapped. The H2-R, as does its streetgoing counterpart, runs like a big fourstroke, pulls strongly from just about anywhere in the range, and isoutstandingly easy to ride.
True, the horsepower and 175-mph potential are frightening, but the mildly tuned engine is extremely flexible, tractable, and doesn’t mind too much getting down low on the power band and doing some good, hard pulling.
Most present-day two-stroke racing machines have very narrow power bands. The rider must always concentrate completely on keeping the engine “on the pipe” and selecting the precise gear and gear change everywhere on the circuit. Once off the power band, considerable time can be lost getting the engine back on good power.
FAT POWER BAND
The H2-R, with its large displacement, produces a large amount of torque well down in the rpm range. In fact, the recommended racing power is from 6000 to 9000 rpm. Considering most racing two-strokes offer about one-third that range, it can be understood that the H2-R is a real “torquer.”
Even below the recommended 6000 rpm the engine is eager to work. Subsequent starts showed that the machine could be driven away from a bump start with almost no clutch slip, and from 4000 on up the scale there was progressive power increase without a sudden lunge at the bottom of the recommended power band. Kawasaki’s racing chief, “Mike” Mizumachi was more than a little pleased when 1 told him it was like riding a tractor; that is exactly what he has prepared the machine to be.
Realizing that a sharp power band would probably even send the Jolly Green Giant into orbit the first time he inadvertently came on the ports abruptly, Mike opted for mild, almost standard port timing. Both inlet and transfer port timing have been left standard at 75 and 58 degrees respectively. The exhaust port has been raised by only 4mm, from 93 to 89 degrees. The almost standard exhaust port timing allows the H2-R to achieve about the same gasoline mileage as the current 500-cc racers used by DuHamel and company this year, about 1 1 mpg.
SOME STANDARD COMPONENTS
There are no special racing cylinders for the H2-R, something that will interest the private tuner. The small exhaust port change can be easily accomplished with the standard casting. The cylinder heads also are standard and unmodified, because the machine in its present form runs on the standard 7.5:1 (corrected) compression ratio. Throughout the machine, in fact, there is a disappointing lack of exotic castings and materials.
KAWASAKI'S 750-cc H2-R ROAD RACER
The Editor Test Rides Kawasaki's 175-mph Weapon And Discovers A Big, Fat Power Curve.
IVAN J. WAGAR
The beefed-up clutch features a special hub to accept 13 plates in place of the 10 normally found on the roadster. Internal gearbox ratios have been changed to range from a 1.7:1 bottom gear to a 0.825: 1 top.
With an overall top gear ratio of 4.15, the H2-R has been averaging 170 mph at the high-banked Yatabe oval track in Japan, about 5 mph faster than the fastest recorded speed at Daytona last year. It is at these higher speeds that the heaviness of the front brake assembly can be felt in the form of a mild waggle.
The machine I rode featured a dual disc front brake, instead of the 250-mm Fontana four-shoe unit normally used by Kawasaki. The test riders prefer the hydraulically operated discs. There was a tendency for the disc to be a bit grabby when cold, and even though this situation disappeared when the cast iron discs warmed up, it was a bit unnerving at first. There is no doubt that the front brake is incredibly good. There is no doubt also that any more stopping power would be very difficult for any rider to cope with on a twisty circuit.
DISC BRAKE CHANGES
But along with the advantages of superb stopping power, there is a weight penalty with the dual disc assembly; no less than 10 lb. have been added to the front wheel. While this additional weight is nice during early gear changes, it is unsprung weight, thus creating the tendency for the slight oscillation at high speed. Due to be tried the week after I left Japan are a pair of 5-mmthick discs in place of the 7-mm units on the machine I rode. The thinner discs will be much lighter and will still be sufficiently resistant to warping. Very minor chassis tuning will eliminate any remaining heaviness after the thin discs have been tried.
One fact that emphasizes the front wheel weight is the lightness of the whole machine. With a claimed dry weight of only 310 lb., the H2-R feels like the 500-cc Hl-R and offers a power-to-weight ratio that will be envied by its competitors.
Testing at Yatabe is being carried out with a fuel/oil mix, rather than using straight gasoline and the oil injection pump. NGK B 10.5 EN plugs have proved sufficiently hard for the sustained high speed running already completed, while offering good clean running at low speed, tight circuit testing.
Chassis modifications thus far are quite mild also. A racing frame is used on the H2-R which bears little resemblance to the street frame, but the all-heli-arc-welded, chrome-moly chassis provides high strength, low weight, and is almost identical to the now famous Hl-R frame. Whereas the Hl-R has featured Ceriani front forks, the big version has gone to a Japanese assembly. The forks were constructed by Kayaba in cooperation with Kawasaki racing engineers, and have provision for dual disc brake mountings.
TO RACE OR NOT?
Now the big question: Will it race at Daytona? The answer will come from a man named Bob Hansen. Bob, the current vice-president of the AMA, will be leaving the employ of Kawasaki Motor Corp. to operate a completely independent racing shop for the bright green racers.
It would be very difficult to find anyone more qualified for the job; two years ago when Honda came to Daytona with the 750s, Bob, acting quite independently of the factory effort, managed to pick up Dick Mann to ride a spare bike. The story is history now. 01’ Bugs was sort of commissioned out by the folks at BSA and was available. Hansen, for whatever reason, was not chosen by the Honda people to head up the racing effort, despite his nine years with American Honda, and twice that many years in AMA racing. Bugs won the Daytona 200, while the three offi cial bikes failed before the halfway mark.
There is sort of a parallel when we look at Hansen's effectiveness at Kawa saki this past season. It is not just coincidental that the bright green racers really came to life in 197 1. During Hansen's tenure at Kawasaki, the H1-R became the Hi-RA, the incredibly fast mount used by Yvon DuHamel when the rail birds began making predictions after his near victory at Pocono. By raising the compression ratio from 7.5 to 8.0: 1 and raising the exhaust port timing, Kawasaki engineers changed the H1-R's 6000 to 9000 rpm power band to 8000 to 10,000 for the model A. While the new machine proved more difficult to ride, it became a jet. So much so, in fact, that Yvon went to Talladega with power to burn.
A SPECTACULAR PERFORMANCE
Faced with two pit stops, the wiry little Canadian motored away from the pack at more than a second-a-lap advan tage, until he had the necessary 20-plus seconds in hand. Aided by the ultra fast fueling device in the Kawasaki pits, Yvon joined the fray still in the lead, and by the time he made his second stop he did not need a time advantage. Yvon, riding a 500, won by over a minute, despite his two pit stops. Cer tainly one of the best performances ever in an AMA road race.
Yvon and the Hl-RA were no less spectacular at the season's ender at Ontario. Racing wheel-to-wheel with Gary Nixon on a special lightweight version of the Triumph racing Three, Yvon never bothered to slipstream his 50-percent-larger-displacement competi tor.
However, every lap as the two riders passed the 100-mph barrier, Yvon simply drove away. The contest was close because Gary Nixon put in one of the very best rides of his whole career, and the Triumph had a better power band in the twisty infield. A power band almost as good as the new Kawa saki H2-R.
At this point it would seem that there would be no question about Han sen opting for the new machine. But there is. Hansen has been around racing for too many years to be completely carried away with the prospects of something new. He believes that if you have something you know is good, and you have to finish to win, why change.
THE BIRD IN HAND
[his might be a good philosophy in this case. After all, Yvon had the fastest machine at Ontario, it is dead reliable, and the riders, Yvon, Ralph White and junior rider, Mike Lane, are most famil jar with the Hi-RA. It's sort of the old "bird in the hand" bit. Hansen is extra cautious about the new machine be cause none of our riders have ridden it, and, at this writing, it looks like several weeks before one is flown over for evaluation in this country. As Bob said, "You first lound eyes to lide new lacing machine. You journarist, onry former lace lider. Opinion no good."
Whatever Bob Hansen decides, there is one thing sure: the folks at the factory are looking ahead. Hardly had the H2 become a reality and the racing engineers were playing with a super performance version for AMA racing. It will be most interesting to see if Hansen will start the season with the proven, but somewhat difficult-to-ride H 1-RA, or the big bore secret weapon residing peacefully at Akashi.
