Air-cooled cylinders (most especially two-stroke cylinders) and cylinder heads, plus all kinds of pistons, are especially liable to cracking because they run hot and are wracked by thermal as well as mechanical stress.
At Talladega in 1971, my rider Cliff Carr put our H1R Kawasaki on the front row. As I rolled the bike onto the grid, Steve Whitelock, Yvon DuHamel’s mechanic, said, “What’re you doing here?” For once, I had the presence of mind to say the right thing. “We belong here.”
The physics of materials said otherwise in the race—a head cracked, allowing its copper gasket ring to blow. Here’s how. As the engine runs, the center of the head is heated to high temperature by its exposure to combustion, but the outer parts of the head—its array…
