Indian Motorcycle “Gilroy” Powerplus 100 Engine Service Manual (2002-2003)

Indian introduced the Powerplus 100 for the 2002 model year as the new engine for its redesigned Chief. The 100-cubic-inch V-twin replaced the S&S-based engines that had powered the revived Gilroy Chief since production resumed in 1999. Contemporary Cycle World coverage described the Powerplus as Indian's new proprietary Chief engine and noted that Scout and Spirit models continued with their existing 88-cubic-inch S&S engines.

The engine retained the traditional American 45-degree V-twin layout but was deliberately styled to give the revived Chief a stronger visual connection to historic Indian motorcycles. Its rounded cylinders recalled earlier Indian Chief engines, while the carburetor was relocated to the left side of the V. Indian used a 42 mm Mikuni flat-slide carburetor, electronic ignition and a 100-cubic-inch displacement of approximately 1,639 cm³.

Development involved Indian engineers together with outside engineering specialists. Contemporary reporting identified Thunder Heart Performance in the early development work, followed by VePro for final design and durability development, with Lotus Engineering involved in sound and emissions testing. Production engines were built in Michigan by Performance Assembly Solutions.

The Powerplus became the defining engine of the final Gilroy-era Chief generation. It powered Chief-family motorcycles through the company's final production period in 2003, including models such as the Chief, Deluxe, Roadmaster and later Chief variants. The separate 2003 factory Chief and Chief Vintage manuals both document the Powerplus architecture in their complete motorcycle service procedures.

Production in Gilroy ended abruptly in September 2003, when Indian Motorcycle closed its factory after additional financing failed to materialize. Approximately 380 employees were laid off, bringing the Gilroy phase of Indian production to an end.