We’ve all heard of the butterfly effect—the notion that a disturbance as small as that caused by a butterfly’s wingbeat may trigger a chain of events leading to formation of a typhoon. We know from watching laminar (straight-line) flow of a fluid that something unseen in that flow—a random eddy, a slight imperfection in a surface—can trigger the appearance of instability, causing the whole flow to become turbulent.
The case I’m interested in is the reputation of Kawasaki’s 1970–71 500 H1R production roadracer for evil handling. Conversation on this at one time rivaled the certainty of some old-timers that Vincent motorcycles had “a hinge in the middle.” Other old-timers would speak up in defense, saying, “Ah, poor you—your bike must have been made on a Monday. That was Reggie Cogg-Willoughby’s day off. No one but old Reg could fit the fork-link bushings properly.…”
Long after the initial impact of the H1 and subsequent H1R roadracer had become history, I had one of those 500s in my shop. As I went through the parts I did my usual test on its two rear suspension units: Removing the spring and checking for normal damping. Normal is not much on compression, good steady resistance on rebound. One of the two passed. The other had nothing; I could pump the damper rod in and out with zero resistance. Think of trying to race such a bike—with half the normal damping, and that half all on one side, twisting the swingarm at every bump.
Unlike the production suspension units, which were assembled by welding, those “racing shocks” could be disassembled by unscrewing the threaded top of the damper body, through whose center hole the damper rod moved in and out. When I did so, the first thing I saw was that the O-ring seal for the threaded top was present, but not in its groove. During assembly, rather than smoothly sliding against the damper body as the top was screwed into place, that O-ring must have gripped the other surface, flipping into a C-shape. When the bike was ridden, the damping oil saw its big chance for freedom and escaped.
Finding that his bike handled terribly, just as his skeptical friends had told him, for some reason the owner did not put the stock units aside in favor of Konis or Girlings, but just continued to ride it as it was, knowing that such terrible wobbling was normal. Man up and gas it!
Not true! My rider in 1971, the late Cliff Carr, won many races and useful money on our H1R, which did not wobble, and which at a Danville, Virginia, non-point national was a good match for the light and nimble Yamaha TR2-B of Kel Carruthers. Kel eventually won but it took him some laps to get by.
What was the difference? Cliff’s ride had a pair of veteran Koni dampers on it, which at each change of springs (60/90s for most tracks, 100s for Charlotte’s small bowl) passed the “Is there normal damping?” test.
I have sometimes said to people at the track, “If you can ride, and if you’ve done everything perfectly, you might be in with a chance.” Installing O-rings correctly is definitely well within our human capabilities. Riffle through your copy of the Parker O-Ring Handbook to where it recommends lightly greasing the rings immediately before installation. Why? So that, as the parts come together, the O-ring will lie nicely in its groove and settle down to a lifetime of normal sealing, rather than take up some abnormal position in which its ability to seal is compromised.
In the case of the first space shuttle loss, the problem was diagnosed as an O-ring which had an important role in sealing the Solid Rocket Booster (SRB) sections together. Too cold and stiff to quickly be pushed into position by the sudden pressure rise as the booster ignited, flame is imagined to have bypassed the out-of-position ring, burning it enough to prevent it from sealing. Continued passage of hot gas led to a major leak and fatal damage to the nearby liquid propellant tank, with tragic consequences.
For a time after that I carried three O-rings in a pants pocket—the usual black Buna-N common in engine applications, a white Teflon O-ring, and an orange Viton II ring, originally made for an application similar to that on space shuttle’s SRBs—the Viton ring for use as a head gasket to seal extremely hot combustion gas in Yamaha’s TZ roadrace engines.
Getting back to the H1R that passed through my shop: The flutter of the butterfly’s wings that caused it to end up unloved and rusting outdoors at the edge of a farmer’s field was the incorrect assembly of one of its rear shocks by an outside supplier. Just rubbing the O-ring with greasy fingers would have resulted in a successful normal installation. Instead…