The S&S IST ignition system has a variable rev limiter which is preset at 6250 rpm, but can be reduced or raised to a maximum of 7200 rpm using the optional S&S Guardian™ Diagnostic System software. The ability to reduce the rev limit is very attractive to owners of balanced Harley-Davidson® Twin Cam 88B™ engines who are concerned about damaging the balancers by over revving. Here's how the rev limiter works. When the engine speed reaches the rev limit, the module goes into a "stutter-fire" mode (a noticeable but not severe combination of fires & misfires). Should the engine speed continue to increase to 256 rpm above the rev limit, the ignition stops sparking the engine until the engine rpm falls below the rev limit. A break-in rev limit program is also available to protect new and rebuilt engines from damage. When this feature is enabled, using the Guardian Diagnostic System software, the initial rev limit is set at 4250 rpm, and increases in three steps, reaching the maximum of 6250 rpm when the engine has accumulated 24 hours of operation. Once enabled, the break-in rev limit program cannot be canceled. It should be noted that IST ignition modules sold with complete S&S engines are slightly different in that they have a maximum rev limit of 6250 rpm and the break-in rev limiter is enabled. The maximum rev limit in those modules cannot be increased.
The new S&S Intelligent Spark Technology ignition system can be installed quickly and easily without permanent modifications to the stock wiring harness on 1994-' 06 motorcycles. S&S wiring harness adapters plug directly into the stock wiring harness of late model carbureted motorcycles. 1986-' 93 Sportster® models along with 1984-' 93 and some 1994 big twin models require minor wiring harness modifications. Once the system is installed, it requires no adjustment. Ignition timing is automatic. You don't need a timing light.
- Simple installation – installation kits plug into stock wiring harnesses.
- No timing adjustments – the system adjusts timing automatically
- 6250 rpm rev limiter adjustable to 7200 maximum with Guardian Diagnostic System
- Single fire operation – requires two coils or dual coil package
- High output – automatically maximizes coil output
- Automatic dwell adjust – will optimize current for any 0.5Ω to 3.0Ω coil
- Short circuit and reverse polarity protected
Diagnostics – scan tool, harness jumper, or Guardian™ Diagnostic System
Optional Guardian Diagnostic System allows engine builder increased flexibility and control
Speedometer calibration in 2004-' 06 models requires Guardian Diagnostic System
The same IST module is used for all engines. Installation kits are available that allow connection to the stock wiring harness for specific applications.
*Installation Kit Required. See IST® Installation Kit chart. Do not use a dual fire coil with the S&S ignition module.
This kit will NOT work with vehicles equipped with flat slide carbs, open
primaries, and dry clutches. If you want to use IST with these configurations,
contact S&S – we can help set-up IST.
The S&S IST Ignition System is not recommended for kick start applications
unless a cam position sensor is used. Engines using a crankshaft position
sensor only will be difficult to kick start. We recommend our Super Stock®
ignition system for kick start applications.