Inside Harley's Milwaukee-Eight Motor

CHECKING OUT THEIR 4-VALVE HEADS

- John Sullivan

THE MILWAUKEE-EIGHT’S COMBUSTION CHAMBER IS A 4-VALVE DESIGN. THIS IS A MAJOR IMPROVEMENT OVER THE TWIN-CAM’S 2-VALVE SYSTEM. HAVING TWO SMALLER INTAKE VALVES IN EACH COMBUSTION CHAMBER IMPROVES THE MOTOR’S LOW RPM PORT VELOCITY; YET THEIR OVERALL SURFACE AREA IS GREATER THAN THE TWIN-CAM’S SINGLE VALVES, WHICH IMPROVES THE MOTOR’S CYLINDER FILL RATE.

ALONG WITH THE SMALLER VALVE SPRINGS, THE TOP OF THE NEW CYLINDER HEADS HAS FOUR RAISED MOUNTING STANDS THAT THE ROCKER ARMS ARE BOLTED TO.

With the 2017 introduction of their Milwaukee-Eight motor, H-D finally stepped into the twenty-first century! The major reason for saying this is, that’s when they fitted their big-twin powered bikes with a completely new motor, which they named the Milwaukee-Eight. For the regular Softail and touring line-up, it displaces 107-cubic inches and in their CVO and performance bikes, it has 114-inches of displacement. Along with the larger displacement, it had several new features: one of which is that it has four valves and two spark plugs per cylinder.