S&S Cycle IST Ignition System for 1984-1999 Big Twin and Custom Applications - Manual (Page 11)

1970, the first year for the nosecone mounted ignition. This is not the case. Currently, the IST ignition is limited to 1984-up carbureted engines. The IST
ignition requires input from an engine temperature sensor, not available at this time for pre-1984 shovelhead engines.
8. Motorcycles with a 7-pin connector instead of 8-pin connector
Some Harley-Davidson® motorcycles manufactured between the years 1991 and 1994 had a 7-pin connector in place of the 8-pin connector.
A 7- to 8-pin adapter is available through aftermarket sources such as Drag Specialties, and Custom Chrome. It is a universal adapter that
allows many different ignition systems (including the S&S IST ignition) to work on motorcycles with a 7-pin connector.
If the IST installation is on a motorcycle with a 7-pin connector, an adapter can be purchased separately.
NOTE: If using a 7- to 8-pin adapter plug, the IST wiring adapter is not needed.
9. IST Wiring Adapter Components
The included adapter kit is composed of two sub assemblies: The power harness, and the cam harness. See Picture 16, below left.
a. Power harness (55-1540)
The power harness connector has an 8-pin connector that plugs into the matching connector of the Main IST harness. The power harness
has three wires coming out of it: chassis ground, switched ignition power (battery +), and tachometer signal. Only two connections to the
motorcycle are required for the ignition system to operate: chassis ground, and switched ignition power (battery +) The tachometer trigger
wire is optional. See Picture 18, next page.
b. Cam harness (55-1530)
The cam harness connector has a triangle shaped 3-pin connector that plugs into the matching connector of the cam position sensor. See
Picture 16, above left.
10. Connect the Power and Cam Harnesses Together
a. Pull the green locking wedge out of the front of the power connector with a pair of needlenose pliers. See Picture 17, above right.
b. Remove the white plugs from the back of the power connector in positions shown. See Picture 18
c. Insert the three leads coming out of the cam harness connector into the back of the power harness connector in positions shown. See
Picture 18.
d. Re-insert the locking wedge into the front of the connector. See Picture 17.
e. Install combined wiring harness onto motorcycle, make any corrections in wiring lengths by cutting and splicing using supplied
connectors.
NOTES:
• Installer to source appropriate wire for any additions. Use supplied shrink tube and wire cover to insulate and protect wires and
connections.
• Stagger any splices in a wire harness bundle. This reduces the chance of wear between adjacent splices. It also makes it easier to pass splices
wire through the harness sleeving.
11
Picture 16
Power Harness
Cam Harness
Picture 17
Connector Locking Wedge