Back in olden times, a cross that had to be borne by riders of British twins was the chronic loosening of the big nuts that held the exhaust pipes against their gasket rings in the cylinder head. Each pipe had a lip around the head end and behind this lip was the threaded ring. If the nut loosened as you rode, dark exhaust residue would dribble from the bottom of the connection.

If you think about this, there was never any way those ring nuts could stay tight because one end of the pipe was connected to the vibrating engine while the other end was bracketed to the relatively calm frame. Some people took to safety wiring the pipe-retaining nuts, but that didn’t stop the dribble of leakage; the relative motion between pipe and engine beat the gasket thinner and thinner, letting it leak.

One European rumor tells us that MZ two-stroke impresario Walter Kaaden originally started the practice of using tension springs to hold the exhaust pipe in a kind of labyrinth socket attached to the engine’s exhaust port(s). He did this, so goes the story, because it sped up the testing of a large series of pipes on the dyno. I suspect that several people in need invented this idea almost simultaneously.

Observation of engines screeching on the dyno revealed that, at certain revs, those retaining springs vibrated like bowstrings.

Back in the early 1960s, Yamaha had the same problem with its two-strokes as the British twins: trying to create a rigid, dribble-proof exhaust connection at the cylinder via a lip on the pipe held against a gasket by a threaded ring. The problem was worse in racing because of the higher operating rpm. Leakage, however, was the least of Yamaha's problem; the pipes also cracked and fell apart from the intense vibration of those 180-degree-firing parallel twins. Yamaha's race department made up pipe connectors that threaded onto the exhaust outlets just as had the previous retaining rings. These connectors had a deep slip-fit groove into which you fitted the exhaust pipe, which was then held in place by a pair of tension springs.

The pipes stopped breaking, but the new springs broke instead. Observation of engines screeching on the dyno revealed that, at certain revs, those retaining springs (two per pipe) vibrated like bowstrings. The fix for that one was easy: Just slip a short piece of rubber hose over the spring to act as a damper. The bowstringing was gone, but the springs now broke in a new way, at their ends, where they were formed into hooks. One end of the spring hooked into a tab welded to the exhaust pipe and the other into a hole drilled through a nearby cooling fin.

“Look at those exhaust springs! They don’t have swivels. They’re going to break.” And break they did, one after another.

That one took a bit more thought, but what it boiled down to was that, to stop those springs breaking, they had to be made in three pieces. One was the spring itself. The second was a steel fitting that threaded into the open end of the spring, with a head that slipped into a forked receiver welded to the exhaust pipe. The other end of the spring was wound down to a small diameter. Pushed through this small diameter from the open end was a length of heavy wire terminating in a “button” too big to pull through the end of the spring. After insertion, this heavy wire was formed into a hook. What this swivel construction did was to separate the spring from bending and twisting, leaving those functions to its end fittings. The springs became reliable at last.

Former director of Harley-Davidson’s VR1000 program Steve Scheibe and I were down at the far end of the Daytona pit lane looking at the new Honda RC51 racebikes in their roped-off enclosure. “Look at those exhaust springs!” Scheibe exclaimed. “They don’t have swivels. They’re going to break.”

And break they did, one after another. It was an epidemic.

I’m sure Honda’s racing engineers had known for years how to make no-break exhaust-pipe springs. What we were seeing was either the mistake of a junior engineer or the work of an outside firm that had manufactured the titanium exhaust system.