Here are the common approaches:
* Using the ECU's diagnostic port (most likely): Many modern Bonnevilles have a diagnostic port (often OBD-II compliant, sometimes a proprietary Triumph connector). A tach adapter that plugs into this port is the cleanest and easiest solution. This adapter intercepts the data stream from the ECU and provides a clean RPM signal to your tachometer. This is the preferred method.
* Tapping into the ignition coil wire (least desirable): This is a less accurate and potentially more problematic method. It involves connecting to a wire that is part of the ignition system's primary circuit. You'll need to find the correct wire (often one of the high-voltage wires leading to the spark plugs) and use a special inductive pickup for your tachometer, *without breaking the circuit*. This method is less accurate because it's an indirect measurement of RPM, not a direct signal from the ECU. Improperly done, this can damage your electronics or be dangerous due to high voltage.
* Using an aftermarket RPM sensor (advanced): Some aftermarket RPM sensors can be attached directly to the engine, usually to a rotating part like a flywheel or camshaft. This requires more mechanical work and knowledge.
Before you start:
* Consult your Bonneville's wiring diagram: This is crucial. It will show the location and function of all wires, allowing you to safely identify the correct connection points. You can find these diagrams online from various sources or through your Triumph dealer.
* Consider a professional installation: If you are not comfortable working with motorcycle electronics, it's best to take your bike to a qualified mechanic to have the tachometer installed professionally. Incorrectly wiring it could damage your motorcycle.
In short, focus on finding a tach adapter compatible with your Bonneville's diagnostic port. This is by far the safest, easiest, and most accurate method. If you're unsure, consult a workshop manual for your specific model year and consult a qualified motorcycle mechanic.
