Stage 4 Engine Development and Modification

Stage Four Harley-Davidson engines are "anything goes". If it can be stuffed into a motorcycle chassis, its worth trying. Time, expert knowledge, special tools and lots of money are required to build a stage four engine. These are all out race engines, designed for drag racing and other forms of competition.
These modifications can provide from 120+ horsepower at the rear wheel of a late model Harley-Davidson motorcycle. For these engines, the horsepower is only limited by the available money and engineering skills.