California kart racer Erv Kanemoto was asked to “see what he could do” with a pair of cylinders from Yamaha’s 1965–’66 production roadracer, the TD1-B. As the concept of using all available cylinder wall for ports was already well-established in karting, Kanemoto knew very well what to do: Add another pair of transfer ports. Because there was little thickness of material in the TD1-B cylinders, the best he could do was to cut slots in the cylinder wall, fed through holes that he made through the piston skirts. As the piston descended, raising the pressure of mixture in the crankcase, it would pass through the holes in the piston, up through the slots, and emerge into the cylinder. This modification boosted power and the word got around. Soon Kanemoto was asked to provide samples of this hardware to the Yamaha importer.