Bonneville America Forums Forums Technical Forums General Tech Emergency Start Mod for EFI Bikes

In light of the low voltage cutoff from the ECU, one could possibly get caught in a no-start situation due to a 0.1 v voltage difference at the battery. So, for example, if the battery voltage is 0.1 volt than the threshold, the starter interlock would prevent the bike from starting. There is a simple modification that you could make to bypass that interlock, and start the bike.

I'll start off with great thanks to Ken D'Ecosse of (www.triumphrat.net) that devised a way to install a
bypass switch between the starter solenoid and starter relay. Ken has graciously allowed me to reproduce his
findings here on BA.com.

The America and Speedmaster models have the starter relay located under the fuel tank on the left hand side of the frame backbone. This relay is also known as the Headlight Relay or Headlight Dip-Switch Relay. This relay doubles as a headlight cut-out and starter relay. It cuts out power to the headlight when the starter is operating. There is also a way to install a manual intercept button directly on the relay, but since the relay is not accessible, a bypass switch is a more viable solution.

This Emergency Start Mod would work if your battery may be strong enough to prime the fuel system, but be below 12.6 volts. NOTE: that by using this mod, all safety controls are also bypassed . So. kickstand switch, clutch switch, neutral switch, etc are bypassed, so make sure the bike is in neutral first!

From Ken:

The other way to go would be to connect a 'bypass' switch between the two white/red wires - if you close that
switch the starter power will transfer directly from the start button to the solenoid, again bypassing all the interlocks. In a pinch, if stranded, (even without having a switch installed), you can pull the relay out of the socket & just stick a paper clip across those two contacts. Once started you can remove the shorting link (paper clip)
& replace the relay in the socket to get the headlight back again. Neither of these methods is drawing any serious current through the starter button, just the starter solenoid current (not substantially different from the relay), And generally operation is essentially the same with the starter button controlling the start function.
And by this method you avoid shorting the ECM output to ground - although a well-designed short-protected
output device, just as well not to tempt fate & test that repeatedly!



H.

Hey DEcosse, does this switch operate in place of the Starter button (in which case I would install the switch as Momentary-Off) or does it still require the use of the Starter button (in which case I would install it as an On-Off switch)?

Also - I understand that when this switch is On it bypasses the interlocks. But once the engine is started, would you need to keep this switch On? For example, in the case of a faulty kick-stand switch wouldn't the motor cut out if that new switch was turned off?

How many amps would this switch have to handle?

Hi Richard - the switch only bypasses the change-over relay - you still operate the start button as 'normal' to start the bike.
It does not matter whether the switch is left enabled or disabled after start - that signal (before or after switch) only has power on it when the actual start button is pressed. However I would suggest its purpose is really emergency use and would normally be left off.
The rating for the switch is minimal because it only carries the solenoid coil current, which is couple hundred mA at most.

Let me explain a little better how the OEM circuit works for you, which should hopefully make the bypass easier to understand - refer to my excerpt from the main schematic that hyates posted above:
The initial condition after turning on ignition, has +12V on the Blue/Yellow wire coming from the left side of diagram to pin 3 of the Starter Relay (item 38); That is the 'common' pole of the Relay change-over switch; in the initial condition, the relay is NOT energized, but power is transferred through the N/C (Normally-Closed)contact pin 4 - the blue wire to pin 4 then carries +12V off to the headlight.
Now, in starting mode, Power from the normal 'start' button (on the right bar switch assembly) comes in on the white/red line from the left side of the page - that line goes to +12V when the button is pressed and feeds into pin 1 of the Starter Relay (item 38); However - that is only half of the requirement - in order for the relay to energize, there must be a 'ground' (from the ECM) on the Yellow/Brown wire at pin 2. When there is both +12V and 'Ground' at same time on the relay, it energizes and the power from the 'common' (pin 3) is now transferred to the NO (Normally-Open)contact pin 5 instead of pin 4. That has the simultaneous effect of removing power from the headlights and at the same time applying power to the starter solenoid (item 36) via the second white/red wire.

So by employing the switch, we bypass the relay entirely and power goes directly from the start button (when pressed) to the starter solenoid. If the bypass switch is enabled (or not) the relay will still energize however if all the interlock requirements are made (incl the low voltage threshold) thus turning off the headlights for improved starting conditions.

The emergency bypass switch circuit is installed and works great - thanks DEcosse. There are pics of the installation on this thread here. which I incorporated into a switch box with other functions.

Awesome work!

H.