Technical information on stock engines for Harley-Davidson motorcycles.
|Motorcycle Performance Guide is now
providing tuning information for Harley-Davidson Twin Cam 88 and EVOLUTION engines. For
Twin Cam 88 engine information, look for the TC88 label next to the horsepower number.
Stage One Harley-Davidson engines involve no
internal changes to be made. All modifications are made by bolt-on changes or
modifications to external components on the engine. These components include air cleaners,
carburetors, exhaust systems and ignition systems. No special tools or training is
required to perform Stage One modifications.
These modifications will provide from 55 to 66 horsepower at the rear wheel of a late
model 80 CID Harley-Davidson big twin Evolution engine.
All the parts listed below are traditional Stage One
components. The components listed have all been tested on Harley-Davidson engines. When
installed and tuned properly, these components will improve the rear wheel horsepower of
your big twin engine. Some popular, traditional items are not listed here. Components that
have not been tested or did not improve the rear-wheel horsepower in testing various Big
Twin engines are not listed. An example of components not being listed are drag pipes.
Drag pipes, even when properly tuned, will not improve the street performance of your
Recommended Parts List for Bolt On
Screamin' Eagle Air Cleaner Kit
K&N Air Filer
Stock Keihin CV (Modified by one of the following methods)
- Harley jets with 'do-it-yourself' modifications
- DynoJet carburetor re-calibration Kit
- DynoJet ThunderSlide Kit
- Yost Power Tube
Screamin Eagle 44mm CV
Screamin' Eagle Slip Ons
Cycle Shack 2-2 Slash Cuts