Harley-Davidson's association with sportbike manufacturer Buell Motorcycle Company began in 1987 when they supplied Buell with fifty surplus XR1000 engines. Buell continued to buy engines from Harley-Davidson until 1993, when Harley-Davidson bought 49 percent of the Buell Motorcycle Company. Harley-Davidson increased its share in Buell to ninety-eight percent in 1998, and to complete ownership in 2003.
Whether it is a mechanical, hydraulic, flat tappet or roller style, the lifter is one of the most important components in the engine. The lifter technology determines how the camshaft will react to the rest of the engine combination. And the technology that goes into it is simply amazing.
Most cars use hydraulic valve lifters that rely on oil pressure to maintain a tight clearance between the camshaft and rocker arm. If the pressure isnt right, there is play between the lifters and the rest of the valvetrain, which causes a noticeable tap. Its possible that cold oil at startup may help pump up the lifters, but at normal temperatures the viscosity drops, and may be too thin to correctly work the lifters. As the oil breaks down after a few thousand miles it thickens, which eliminates the noise.