Avoid the Magic Smoke

[Kiwi_Roy]

I know of several bikes that have badly damaged the loom while cranking because of a bad main ground (battery negative) connection, I think this particular V11 with the ground under the seat lock is a likely candidate.

 

If the main ground gets disconnected in some way the heavy starting current tries to find an alternate path back to battery negative. The obvious alternate path is the small black wire from the Voltage regulator case all the way through the main loom to the battery, a few seconds at starter current is all it takes to heat this enough to melt through the insulation of any wires it touches grounding them out.

Other paths might be additional grounds added to headlight or accessories.

The ECU also has a ground to the battery but I think it's isolated, see check below.

 

How to avoid letting out the magic smoke

Cut the black wire at the regulator and disconnect it at the battery.

Connect the regulator chassis to an engine bolt with a short jumper, this will provide a better path back through the engine to the main ground, you might even notice an improvement in charging.

 

Check for other ground paths by disconnecting the main ground wire.

With the key on the bike should now appear dead, if it looks normal don't try cranking whatever you do, try to trace the wires and get back.

 

 

I suggest wait a few days to see if there are points I missed before diving in

[luhbo]

... I think this particular V11 with the ground under the seat lock is a likely candidate....

 

I know of only one bike being so sadly treaten: your's. Did you buy it knew from the factory or can you tell any previous owner who might have screwed that up?

 

Hubert

[helicopterjim R.I.P.]

For some of us who may be electro challenged perhaps some pictures will be helpful with understanding what exactly needs to be done ....

[helicopterjim R.I.P.]

Oh ... and there has been at least one other I know of that has gone up in smoke ....

 

Sent from FRED (Fricking Ridiculous Electronic Device)

 

 

[Kiwi_Roy]

Here's a partial diagram taken from the owners manual, I modified it a little just for clarity and to show how it really is.

                    

The first version shows the Normal path for the current returning from the starter to battery via the main ground

Below that I show how the current diverts to the small regulator ground if the main ground works loose.

 

 

 

If you look closely at the regulator on the bike you will see a small black wire going from one of the holding bolts, it goes all the way through the main loom to the battery Negative post, this is the small ground wire shown on the schematic (it bolts straight to the battery post not exactly as the schematic shows)

The regulator is also grounded through being bolted to the horn bracket which in turn is bolted to the chassis.

 

 

Picture 1

The wire that drops straight down from the battery on the drawing is the main ground, this on my bike ran direct from the battery post to the seat release bracket where it's sandwiched neatly between bracket and the gearbox held in place by a small Allen screw as shown. 

(I believe this is stock for North America)

 

If the seat release bracket works loose over time it's possible for the main ground to break contact, now the ground path diverts to the small black wire from the regulator case to the battery. The normal starter current is about 150 Amps no problem for the main ground but too much for the small innocent looking black wire resulting in Voltage drop less current and weak cranking.

Unfortunately a side effect of Voltage drop is heat, enough to cause this small wire to release it's magic smoke and a melt down in the loom if not a fire under the tank.  

There may be other alternate grounds which will suffer the same fate, I know of one bike where the tiny ECU ground had a similar melt down. It will only happen with a wire that's also grounded away from the battery post, accessories like heated gear are ok because they are isolated.

 

Picture 2

If you leave the main ground where it is just make sure it's kept tight, I moved mine to an adjacent gearbox bolt where it's more secure and I can keep an eye on it.

 

 

Picture 3

Here you can see the results of letting out the magic smoke as I described, this owner was fortunate the bike didn't completely self destruct. You can see the black wire insulation has completely gone and a spot on the small white wire where it burnt through

 

 

 

BTW The ground connection from regulator to battery seems to be common to all Guzzis from 1998 to 2002. I suspect this wire was added to cure weak charging as the case to chassis joint corrodes. it doesn't do that well either, too much resistance.

[helicopterjim R.I.P.]

Thanks Roy.