It's Not How Big...
IT'S NOT HOW BIG...
ROUNDUP
Motorcycles get classified, just like motorcyclists, but it’s always seemed more reasonable for bikes to get labels because it’s the motorcyclists who do the labeling. The subject came up as we were labeling the 550cc motorcycles compared elsewhere in this issue. Most of the motorcycles ridden by most of the riders on the staff are larger displacement machines because big bikes do everything so easily and are so convenient to ride.
Compared with any of the current big bikes, most of which seem to be around llOOcc, the 550s are little. They weigh about 100 lb. less than most of the socalled superbikes. Their engines are half as big in displacement. The only category in which the 550s aren’t substantially smaller than the 1100s is in performance.
To put things in perspective, consider some numbers. Not just any numbers, but numbers for quarter mile acceleration, mileage, weight and wheelbase. These 550s do the quarter mile in about 13 sec. at 100 mph, with the fastest at 12.70 sec. Weights are about 465 lb. for the big ones
and one lighter at 424. Mileage is around 50 to 55 mpg. Wheelbases are about 57 in. By today’s standards these may be classified small-to-medium size bikes. They are at least two steps away from the biggest motorcycles and not likely to intimidate too many riders.
Now let’s turn back through the pages of old Cycle World magazines to the original Kawasaki Mach III. That was a startlingly fast motorcycle, faster than much bigger bikes of its day and able to zip through a standing start quarter mile in 13.20 sec. at 100 mph, according to the first test in Cycle World. Its 415 lb. weight was much lower than current 550s and so was the 36 mpg mileage lower than current standards.
Within a year after the Mach III came Honda’s CB750 Four. It was an overwhelming motorcycle with its four carburetors and all that speed and size. It could turn the quarter mile in 13.38 sec. at 100 mph, return 35 to 40 mpg, weigh 499 lb. and it had a 57 in. wheelbase. The size and performance were right in the middle
of today’s 550 figures, or only a little heavier and slower. It had a harder suspension and didn’t handle as well, either.
The next superbike to gather records was Kawasaki’s 750 Triple, the Mach IV. Provided the rider could keep the front wheel on the ground, it would steam through the quarter mile in 12.72 sec. at 104 mph. It also could get 20 mpg when ridden hard, it weighed 465 lb. and had a 55.4 in. wheelbase, making it quite comparable to today’s 550s in size and performance while using twice as much gas.
Several years later Suzuki came out with the GS750, a bike very much like the GS550 in design, and its performance level was about the same as the average 550 today, though it weighed 511 lb. It wasn’t until the latest generation of 750s, bikes like the current CB750F and GS750E and KZ750, that 750s became low 12 sec. quarter mile machines.
Okay, so they’re fast. As surprising as the speed of these four bikes is the tractability. There have been peaky bikes in the past that were very fast for their size,>
but these machines aren’t like that. Through such things as Yamaha's Y ICS and Kawasaki’s very light valvetrain that enables exceptionally fast valve opening and closing, the low-speed running of all four of these 550s is exemplary. And because of the gearing of these machines the top gear acceleration is comparable to that of much larger motorcycles.
With gearing arranged so that these 550s are spinning at around 5000 rpm at 60 mph, they are right at the base of their powerbands. Because of this gearing the roll-on performance of these bikes is a match for most large displacement dressers. For instance a Kawasaki KZ1300 has about as much torque as any machine on the highway and because of its load and gearing it requires 5.2 sec. to accelerate from 40 to 60 mph and 7.0 sec. to go from 60 to 80 mph. A GPz550 can accelerate through the same speeds in 5.2 sec. and 6.3 sec. The Yamaha Vision is even quicker on roll-ons, with times of 4.9 sec. and 5.6 sec, mostly due to its lower gearing.
For the same reasons, big bikes don’t suffer much difference of fuel mileage on the highway. Normally, bikes like these 550s will get lower mileage on the road than they do on our mileage test that’s half in the city and half on the highway. Bigger bikes go the other way, getting better mileage on the highway, so most of these 550s would dip down into the high 40s on long rides, about the same mileage most of the 750s or 1100s get on the road.
Comfort equalizes for the same reasons. Big inline Fours have more vibration than little Fours, so the slight differences in gearing don’t make most of the big bikes noticeably more relaxed on the highway. Our collection of test 550s all had useable seats, better seats in fact than many larger bikes have. The combination of good seat, good seating position, lowvibration and easy working controls made most of these machines every bit as nice a touring bike as most of the motorcycles called touring bikes.
So what’s the difference? Maybe it's not how big the motorcycle is, it's how it's ridden.
