My English rider Cliff Carr, his wife Diane, and I set off for a CMA road race at Mosport, not far from Toronto, Ontario. Being our first race together, I was hoping our Kawasaki 500 H1-R would run trouble-free

It did not. Coming in from first practice, Cliff told me something was wrong with the gearbox. He couldn’t describe the problem other than that. Gearbox malfunction is serious, for the rider cannot release a locked gearbox with the clutch.
I was also concerned because I had learned a lot about gearboxes recently, and this one had passed its tests for depth of dog engagement, clearance between non-engaged dog sets, and shift throw (there is an adjustment that stops shift motion a millimeter short of the shift-drum’s detented position. This is to prevent giving the gear being engaged from having enough momentum to pass through the detent and into the next gear (double-shifting).

Cliff’s later remarks gave the impression that this last might be the problem.

To restore full confidence in the gearbox, I took the engine out of the chassis and split the cases so that all was revealed by the light of day. All was as I had built it, including the one millimeter gap that prevents double shifting.
Cliff had gone off to find some lunch and when he returned I showed him that the gearbox was as intended by the service manual. I clicked it through all five ratios.

To make it possible to adjust dog engagement depth of individual gears, Kawasaki had listed gearbox shims in a range of thicknesses. I still have them.

Cliff then said, “I’ve been thinking about first practice. I’m not used to gearboxes that shift this easily. I think I may have given the lever a second push. I’m sorry to put you to this extra work.”

The engine went back together and into the frame without hitch and Cliff reported normal shifting. The bike went well and Cliff was launched into the muscular shoulder development that the Kawasaki triples imposed on their riders. Returning to this track in July, Cliff won his races.

Much has been said about the H1-R’s handling (camel, hinge-in-the-middle, &c). Much later I bought a used H1-R that had been left in a field. In going through its parts I found a possible reason for its abandonment.

It was my habit to remove the springs from forks or rear shocks to allow me to stroke the dampers manually, checking for normal operation. One rear unit tested OK – on compression there was some damping, but most of it was on rebound. The other offered zero resistance to motion: there was no damper oil in it.

Unscrewing the shaft seal carrier through which the damper rod moves, I saw that the O-ring intended to seal the carrier to the damper body had flipped during assembly, changing from the shape of an ‘O’ to that of a ‘C.’

This can more easily happen if the O-ring is not wiped with oil before assembly.

Imagine trying to ride a 75 hp race bike with half of its normal rear suspension damping, and that all on one side. Without the O-ring fully in place, the damper oil was soon pumped out. Riders back then accepted such things on the basis that “That’s just how these things are.”

A proper focus on suspension and damping details arrived in the mid-1970s, as motocross racing forced development of longer-travel suspension. Such improvement quickly made its way into road racing, much to its benefit.

My earlier efforts to make sense of a used Yamaha 250 TD1-B revealed its stiff springing. Pulling off a rear spring and fetching the bathroom scale, I used them plus tape measure and drillpress to measure spring rate (which is the amount of force required to compress the spring by one inch). They were 180 pounds-per-inch – suitable for iron street bikes of more than double the weight.
I’m giving these details because they give some idea of what you learn as you try to cope in racing.

Suspension became supple rather than juddery upon substituting softer dual-rate 60/90 lb/in springs.

On another occasion I was asked to freshen-up a much-used Yamaha TD1-C being ridden in vintage races. On stroking its fork legs (removed from the bike) I found that one leg was soft in compression, firmer in rebound—normal.

The other was the reverse – someone had installed the valve body upside-down in one leg, right-side-up in the other.

Experience soon taught me to disassemble even brand new race bikes and check such things. Here are problems discovered:

One wrist-pin clip only part-way in its groove.

Fork with no damping in either leg because grooves for wire locating rings were .005” too shallow.

Oil leakage into a dry clutch, caused by a sharp edge in one part shaving material off the clutch throwout O-ring. A moment with a rubber abrasive wheel smoothed the sharp edge, preventing the shaving and the leakage.

A connecting-rod with a slight twist, causing one piston to show odd marks. I found this on a race-day morning and had to crudely straighten it with a large adjustable wrench. The rider was 4th that day.

Problem # 2 above had caused several bikes at Talladega 1974 to weave at high speed. I saw one bike throw its rider’s feet off the pegs just past start-finish. Another rider came in white-faced and plopped in his lawn chair, visibly shaking.

At breakfast the morning after, Kel Carruthers said, “What we learned this weekend is that in future, we’ll have to put just as much preparation into the chassis as we do now into engines. Maybe more.”

Prophetic. Today the task of race team techs is to adapt the bike in detail to the rider’s style. Nobody works on engines at the track any more – they arrive in little sealed caissons from a dedicated build facility, just as in F1, and teams talk to them in keystroke language.