About this time last year the Fatboy (2007 FTSB with 42380 miles) was up on the bike jack while I replaced the primary seals and inner race in the chain case. Folks on this forum were a major help in getting through that repair, successfully I might add.
Now we have an electrical issue. About 380 miles ago I changed all three oils. When I opened the chain case it smelled slightly burned. The oil was dark as usual, no leaks by the way. I changed the oil and adjusted the clutch thinking maybe it was slipping(?). Bike has been running fine and shifting smoothly.
One morning I hit the starter and it grunted and then began clicking. I checked the battery voltage, 12.9 volts, but when I hit the starter it dropped to 5.9 volts. Put it on the charger and after a couple of hours it started like it was new. Checked the voltage while it was running and it was charging at 14.4 volts at idle, slight increase to 14.6 when reved up. Oh yeah, when it started it blew the engine dip stick across the garage - an ill-fitting after-market temperature reading dip stick that the seat must be keeping in place. Now when I start it with the volt meter connected it cranks at 11.9 volts and starts almost before you can read the voltmeter.
Two weeks later with daily runs to and from work, the beer store etc. it was running fine. This morning no start. Same deal, 12.6 volts battery voltage dropping to 6 volts when I attempt to crank. It would seem that if the battery were bad it wouldn't hold a charge all week. Any ideas?

 

Before you attempt any troubleshooting, you need to make sure the battery is good.

Charge the battery, take it to an auto parts store and have it load tested.

 

Same deal, 12.6 volts battery voltage dropping to 6 volts when I attempt to crank. It would seem that if the battery were bad it wouldn't hold a charge all week. Any ideas?

It's NOT holding a charge though Jimmy. 12.6-12.9v static is fine but dropping to 5.9 or 6v under load of starter is excessive. That voltage will not crank the bike. Getting a reading of 14.4 or 14.6 while running is good though as your stator and voltage regulator are fine. It's time to buy a battery. And a battery tender also. My bikes are always plugged in once the engine has cooled after a ride and I get long life from my batteries even sitting in an unheated garage over cold Canadian winters. It only takes a moment to plug the bike in when not in use. Good luck!

 

As you report it, there could be two issues... don't forget that the triangle of Stator, regulator, and battery are codependent... If one goes bad, it can damage one or more of the other two.

A fully charged battery (static 12.6-12.7 volts), if in good condition, shouldn't drop below 9.5 volts when turning over the engine, if it is a good battery. You report 12.9v static, dropping to 5.9v... that is a classic fail for a load test...

Also, a burnt smell in the primary can mean a bad stator... not a guarantee, but a possibility

My advice:

Remove the battery, charge it up over night, and make sure it's holding 12.6v or more, two hours after removing it from the starter... Then take it to a store, unless you have a load tester, and have it properly load tested while not connected to the bike... This will tell you if you need a new battery..

Once your battery is confirmed to be good (or new battery purchased & installed), disconnect your regulator plug, and test you stator for ground, and then power output. It's very easy to do, and you can find the procedure either by searching this forum, or a general google search.

Let the tests dictate what parts you need to buy/replace...

If both the battery and stator are bad, I would also check the regulator to ensure it is functioning properly and wasn't damaged by the bad stator/battery combo... Last thing you want to do is install a new battery and stator, only to have a bad regulator take them both out...

Good luck with your diagnosis... report back what you find...

 

Well it took quite some time to close out this issue but here is the current status. Pulled the battery, put it on the charger and then the next day took it to the local battery store. The battery checked out good. Discussed it with the tech since the battery is almost 3 years old. He said by my description sounds more like a dirty/lose connection somewhere.
Ran through the regulator and stator checks and both checked out good. Cleaned all connections I could find and made sure everything was tight. The bike has fired up fine ever since. Even after sitting for a couple of days, no starting problems.
I would have felt much better if I had found an obvious problem but, considering the battery's age, I think I will give myself a birthday present of a new battery later this month.

 

Seems like you managed to remedy the issue even though you don't know what it was. Still counts as a win.

I have been chasing an electrical gremlin in my bike for a while and have found numerous suspects but no perpetrator. The last thing I found was a mangled battery ground that was hiding beneath heatshrink wrap. I could feel the bulge of the wires.

 

Based on what you did... I believe you found the problem.....

The battery, regulator, and stator checked out OK.... then you cleaned all connections and ensured they were tight.... You've had no problems since...

I'd say you had a dirty and/or loose connection......

Yeah, it's always good to find an obvious smoking gun....

But in the absence of a smoking gun, being analytical and systematic in your diagnosis and repair, allows you to deduce with a fair amount of certainty, what the problem was....

Good job.... now enjoy riding the bike...!


Note: If the problem were to now reappear, I would start looking for a more hidden issue like KiwiKid shared in his post above...

 

That's a good find...!!

Many people, myself included, would have probably missed that for quite awhile.... and maybe only found it by accident...