A rider came to me at the races, saying, “My bike won’t run. I need some help.” We walked to his bike, talking. I asked the usual questions. He then told me, “I know it’s not the ignition.”

“How do you know?”

“Because a new ignition box is three hundred dollars.”

A mechanic at our shop diagnosed an open ignition stator on a Kawasaki F5, which wasn’t starting. He pulled one from parts – same result. No spark, no run. But when we got down to actually measuring resistances on the two stators, both were infinite on the fine-wire coil. We had to make the leap to accepting that brand-new parts can be defective.
A young fellow on a 500 Suzuki came to see me, saying his bike was making a thumping noise. He started it – sure enough, rapid thumping. But not rapid enough to be at crankshaft speed.

As I was busy, I suggested he lay his bike on its non-primary-drive side so he wouldn’t have to drain the gearbox oil in order to pull the primary cover.

“When you have the cover off, look at the teeth of the big primary gear. You’ll find a bit of aluminum mashed into the space between two teeth. Get tools from my box there.”


We worked away on our separate tasks. At a point he exclaimed, “How did you know that?”

There it was, shiny aluminum. Where had it come from? Maybe from a pulled thread, somewhere in the bike’s service history? I said to him, “Something I do when there’s a repeating noise is try to get an idea of its speed so I’ll know where to look first. A failing wheel bearing (scratch-scritch) is slower-turning than a driveshaft U-joint.

I thereby became Mr. Wizard, and was rewarded by being invited to make one usable H1 crank out of two with one seized con-rod each.

A story I’ve told before came from the great TD2 shortage of 1969. TD2 was so great a step forward that everybody wanted one, so we bought all remaining Kawasaki A1-Rs in stock and sold every one to people who couldn’t connect with a new TD2. I’m not sure it was a good idea.

One buyer took his new A1-R to Daytona. We had advised our customers to install 210 main jets, and had explained the basics of two-stroke engine operation.

This man seized in first practice and brought me the piston and cylinder to look at. Aluminum was smeared on the iron liner.

“What main jets are you running?”

“190s”

“I think that’s your problem – it’s just a little lean.” (and brand-new, and on the track where seizure was always a lively possibility). Put in 210s.”

Off he went. Second novice practice he was back – seized again.

“Did you jet up to 210s?”

“No, I figured, like it’s running real hot, all that friction, it needs more oil.”

“What jets did you run?”

“190s. But I added more oil to the gas. To reduce the friction, make it run cooler.”

I explained how adding more oil to the fuel leans the mixture – because with more oil passing through the already-too-small mainjets, less fuel was passing. The result was an even leaner mixture.

He gave me that “You just don’t get it” look and went off. We were not sharing a wavelength.

In the next session (it may have been next day) he seized again, loaded up, and began the 1200 mile drive back to Boston. I believed I had made a real attempt to explain how jetting controls operating temperature. These were air-cooled engines, normally run a bit rich. Jetting down toward a maximum power mixture produced more heat and a piston and cylinder were united. He had another idea and was determined to work from that.

On the mature MotoGP two-strokes of the early 21st century, cooling was so good that you could jet down until the engine slowed down.

With the limited effect of air cooling, jetting for best power resulted in a bike that was fast for three laps, then slowed down as it became so hot that incoming mixture from the carbs was so heated and expanded by contact with the hot metal that power dropped significantly. It was a compromise to run 1-2 jet sizes rich, but the cooling effect of richness didn’t let the power drop off so much.

In the early days of air-cooled radial aircraft engine development it was common for liquid cooled engines to need 0.5 pound of fuel per horsepower per hour, but air-cooled round engines, with their crew-cut mid-1920s cooling, round engines had to be given 0.65 lb/hp-hr.

The Internet can complicate human/engine relationships because now, so much is made of how we feel rather than of what we can learn. One rider came to my middle son with a running problem, and when it was diagnosed as the usual for older carbureted engines – blocked idle passages – he objected. “I don’t want it to be the carburetors – they’re full of fiddly little parts.”

Every person with mechanical ambitions has to set aside such emotion and get on with the work. I had to teach myself from a book how to set engine ignition timing. When I assembled the tools and performed the rational steps, I was rewarded with an engine that ran well.

When it comes to feelings, it’s also possible to lose patience with oneself. A friend was mounting a new tire on his Yamaha TD1-C’s narrow front rim. Tires had very stiff beads and getting the second one over the rim without pinching the tube called for observation and care. He pinched three tubes in a row and put himself into a rage. Rage is understandable, but it’s not a tire-mounting technique.

I resolved there and then to in future use only short 7-inch tire levers, and plenty of Ru-Glide. If the lever forces are too high, it means something isn’t right. Today we have tubeless tires, saving 2-3 pounds per wheel and reducing tire operating temperature. But there was an intermediate period in which off-season race bikes sat on flat tires because of tiny leaks.

I used to dream of assembling entire brake systems in a swimming-pool filled with DOT-3. Getting the last air out can take time and thought (If I were an air bubble…) but it will be achieved. Move on to the next task.

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