M-Unit on Carburetted Bonneville

We got a new carbureted Scrambler based on Triumph Bonneville T100 to install a new digital controller M-Unit Blue and a Motoscope Classic tachometer from Motogadget. The M-Unit controller is operated using push buttons. We saved OEM switch sets because they are integrated with the front brake master cylinder and clutch lever.

Switch controls

Original carbureted Bonneville has perfect switch sets for the M-Unit controller. This configuration doesn't use buttons for high-beam flashing or hazard lights. Bonneville doesn't have such buttons.

The only switch without a function is the ignition switch. But this switch can be used to stop the engine in the KILL port by soldering one wire so that it closes the circuit when it's off. Switching off the engine on the M-Unit is a bit unusual: right after switching it off, you need to wait for a couple of seconds before the starter button becomes active again. So, the motorcycle cannot be started immediately after switching off.

Ignition control unit

The ignition control unit complicates electrical assembly. It receives signals from the throttle sensor on the carburetor and from the pick-up coil. Outputs: a signal to the ignition coil and to the tachometer, which is correctly displayed on the Motoscope Classic without additional adjustment.

Carburetor heating

The carburetor heating system is a very important system that prevents icing in a carburetor. See “Venturi effect” and gas pressure drop during acceleration in a narrowing channel. The thermostatic switch for carburetor heating is powered directly from the alternator rather than the battery, to ensure that heating is only active when the engine is running.

Starter button logic

The starter can be switched on only in neutral or with the clutch lever pulled and when the motorcycle is not on the side stand.

We recommend not plugging the side stand into the STAND port on the M-Unit because it works poorly; the ignition simply doesn't work when the bike is on the side stand. Also, if you use the side stand on a running engine, the engine will immediately stop. This makes it impossible to warm up the bike while it's parked and makes this feature useless.

To prevent the motorcycle from starting in gear, the starter button must be connected via the neutral and clutch sensors. The connection must be through a diode to separate the clutch signal from the neutral, otherwise, the neutral light on the dashboard will be on when the clutch is pulled.

Overall, the M-Unit is the perfect solution for older motorcycles with tons of relays and fuses. This unit is easy to connect and diagnose; it's resistant to vibrations and water and is not afraid of power surges. On carbureted motorcycles, the controller is especially easy to install, as there is no need to connect an ECU, a fuel pump, a radiator fan, an ABS unit, and a fuel level sensor.

We recommend using new switch sets with push buttons. This reduces the wire bundle thickness on the M-Unit and makes the assembly easier.

We didn't install the speed sensor in the video, since the magnetic brake disc bolt hasn't arrived yet. The procedure is simple and is described in the articles on our website. The dashboard must be calibrated on the go in order for the speed to be displayed accurately.

Installation of Motogadget electrics on injection BMW K100RS: https://stuntex.ru/en/article/k100rs-motogadget-electric

You can find any Motogadget components in our store Stuntex. Contact us if you have any questions!