Ground the Regulator

[Kiwi_Roy]

Looking at the pictures Cottagetone posted of his gasket thread reminded me how poorly grounded the regulator is.

 

 

All the current from the alternator passes to the battery thru the double red wire but it has to pass back to the regulator case to complete the circuit, The case is very poorly grounded thru a long wire back to the battery and rusty contact to the horn bracket. Any Voltage lost in this connection between regulator case and battery negative is subtracted from the battery Voltage.

A short strap between the regulator case and an engine bolt improves the connection, the engine / gearbox is like a massive wire back to the main battery ground at the gearbox.

 

I know of several spine frame bikes that caught fire because the main ground to the gearbox worked loose, the starting current will find it's way back to battery negative through the small black wire from the regulator case, this causes the wire to get red hot and melt itself to other wires in the loom shorting them to ground.

Make sure the main battery ground is securely connected to a gearbox bolt and take the time to scrape and grease the battery connections with Vaseline.

 

Here's a picture one owner shared, the bare wire is the ground from the regulator to battery negative terminal. Fortunately the damage was easily repaired but he had to open up 3 feet of the loom to do it.

The ground on my bike was just under the 4mm screw that holds the seat release lock, luckily I caught it in time and moved it to a gearbox bolt in full view.

 

Here's part of the schematic first showing the starter return current flowing through the correct path at the top.

 

Then with a loose ground at the bottom showing how the current switches to the wrong path through the small ground wire.

Remember, it's not just a loose wire that can cause this, a badly oxidized battery terminal can do it as well, thats why I always rabbit on about greasing the

battery terminals with Vaseline, it keeps the Oxygen from the Lead so it can't form an insulating Lead Oxide layer.

 

 

BTW, another wire that often gets burnt up is the small ground to the ECU case, this happens when owners forget and remove the battery positive first making contact

between a live tool and the ECU case.

[Stick]

Great post, Roy.  Pics look OK from here today (for a change!!)

[stewgnu]

This is one job that keeps slipping my mind... Right! I'm doin it tomo! Cheers for the reminder Roy!

[Kiwi_Roy]

The picture issue seems to have resolved itself.

[Gottagetone]

Thanks Roy!

[sculler2x]

Here is my solution.  I ran a #4 wire from the battery negative to the bolt on the starter.  I ran a #8 wire from the regulator to the starter bolt on top of the battery cable.  this way the start current goes right to the starter and the regulator has a great path back to the battery

 

 

[Kiwi_Roy]

Sculler2x

It's a good idea to run back to the starter but the motor/gearbox have even less resistance than a large copper wire.

Your #8 wire will probably carry the full starting current without getting too hot if the No 4 fell off.

I'm guessing the wire Luigi provided is about equivalent to a #14, it can't handle 150+ Amps as you can see from the picture.

 

Update

On further thought that's a very good idea, if the bolt works loose the circuit from the regulator is broken also, there's no path

back that way either. Go one step further and make sure that no small black wires land directly on the battery.

 

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