They Musta Had An Idea About It

Following through with mistaken thinking

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Technical Editor Kevin Cameron shares his wealth of motorcycle knowledge, experiences, insights, history, and much more.Cycle World

During Canada’s 1950s uranium rush, Roy Smith, a trapper friend of my dad’s, told this story. He was preparing for a next-morning crossing of a lake north of the town of Spanish, Ontario. A considerable storm was whipping up waves so he was surprised when two young fellows were loading a small outboard-powered boat as if about to set forth. The boat was so loaded with prospecting gear that it had six inches of freeboard at most.

“Now, the two of youse won’t be plannin’ to go out in this great wind in that tiny coracle, will you?”

“Yes we are - so much has been surveyed and claimed already, if we don’t get there tonight there’ll be nothing left for us to stake.”

“Youse’ll never make it.”

“Well, we have to.”

At this point my dad cut into Roy’s narrative. “What happened then?”

“Oh, the both of ‘em drowned.”

“But…didn’t you try to stop them?”

“No. They were grown men. I reckoned they musta had an idea about it.”

People can be very strongly attached to their ideas, and neither clear physical evidence nor anything anyone can say will pry them loose.

1969 was the year Yamaha didn't make enough TD2 two-stroke 250 production road racers to meet demand. At Arlington Motor Sports we had bought Kawasaki's last 11 A1Rs and despite their being no match for a TD2 they sold quickly. One A1R customer bought plenty of spares and when March arrived he loaded it all into his van and drove southward.

I next saw him in the Daytona paddock, holding out a seized piston.

“What mainjets did you have in?”

“I got 190s in there.”

“There’s your problem. People with 210s are running well and their plugs are looking good. Put in a pair of 210s and you should be good.”

Off he went. After next practice, here he came again, again with a seized piston in his outstretched hand.

“Did you put in the 210 mainjets?”

“No, I’m still runnin’ the 190s. See, I figured it’s too much heat makes it seize, so I added extra oil to the gas, you know, to cut that friction, make ‘er run cooler.”

I explained as best I could that adding extra oil, by displacing some fuel, actually made his engine run leaner and seize all the quicker.

“Clean up your cylinder, put in a fresh piston and rings, and jet up to 210s. You’ll be fine.”

A third time he came back – seized again. He was upset.

“Did you jet up to 210s?”

“No, see, she’s runnin’ hot and that’s making her seize. So I added some more oil to cut that friction. Anyway, I don’t care – I’m out of parts so I’m packin’ up, gonna leave now an’ drive all night back to Boston.”

Frank Camillieri and I built a home-made 750 H2-R Triple for 1972, its engine modified from one pulled out of a production H2 streetster just before Christmas. On and off, it performed surprisingly well, earning us a lot of attention if not engraved silver pots (Underdogs. Arf.). In the course of the season, here came a person who seemed very interested in building a bike like it. I like the DIY spirit so I told him literally everything he needed to know to make a bike like ours – port heights, pipe dimensions, ignition timing, dry clutch details - everything. Off he went with it all written down. I didn’t see him again for maybe two years, and when I did I asked if he’d built himself a bike.

“I did”, he answered with a hint of tiredness in his voice. “I blew it up a bunch of times and then I kinda …quit working on it.”

Fearing I’d somehow led him astray, I went through the important variables with him. Everything checked. Except compression ratio.

“Yeah, you told me 6.7-to-one but I knew that wasn’t right. You weren’t going to give away all your secrets. So I started at around nine and went from there.”

I had explained to him that two-stroke compression ratio is measured from the point of exhaust closure, and with the exhaust opening at 83-degrees ATDC, that was 49% of the stroke. Therefore this man had given his engine a top-to-bottom compression ratio of 18.4-to-one. Twenty years later there would be water-cooled 250s that could run on that compression, but it was suicide for any air-cooled.

He musta had an idea about it. He knew 6.7 couldn’t be right. Compression in the sixes just didn’t sound racy enough. But to those of us with H2-R experience, we who had seen these engines literally cut themselves almost in half, we who had dumped fragmented pistons and the small-ends of con-rods out of exhaust pipes, 6.7 was the proven maximum tolerable compression ratio for road race.