Regulator failure mode?

[triangleforge]

I replaced the five-year old wet cell battery in my 1998 ST2 last month with an Odyssey PC680 gel cell and was hoping that got at the root of my charging issues, along with going through and cleaning/dielectric greasing all the main grounds & electrical connections. It didn't.

I rode to a meeting last Friday (a short trip, not much to recharge the battery even with a fully functional electrical system), and came out to a dead battery -- it cycled the fuel injectors and  lit the gauges when I turned the key to ON, but would not turn the motor at all. I parked the bike in a safer spot, pulled the battery & took it home to throw on the charger. Before I turned on the juice, I checked and found the battery reading around 11.7 volts. Took it back the next morning fully charged, started the bike and went on about a 20 minute circuit on my way home. About ten minutes in, I pulled over and put the multitester on it again. From idle to 7K RPM I couldn't get it to register more than 12.2 volts -- a couple of months back, the same test would usually register high 13s or low 14s above 4K, which was what led me to hope it was just a tired old battery refusing to hold a charge.

I know I need to upgrade the undersized main wiring on this bike, and I'd like to add a small LCD voltmeter to the gauge cluster so I can keep a closer eye on things. I also know that this year and model is famous for the poor design & placement of the regulator (this bike is on its second regulator/rectifier, which the PO installed in the stock location but with plenty of nicely-done additional venting in the fairing). But before I start replacing more expensive bits, I wanted to check and make sure that this was a normal failure mode for the regulator -- when it goes bad, does the voltage at the battery tend to drop, or does it tend to spike to levels that will damage the battery? And it may be obvious when I dig deeper into it this afternoon, but how do I check the voltage out of the stator, upstream from the regulator, so that I know I'm getting decent output from there?

Thanks!

[Howie]

A regulator can fail and cause either overcharging or undercharging though undercharging is the more common failure.

Anyway, this troubleshooting link is easier than typing paragraphs:
http://www.electrosport.com/technical-resources/library/diagnosis/fault-finding-guide.php
Chris Kelley sells Electrex regulators   http://www.ca-cycleworks.com

If I remember correctly, your bike has a single phase system (two yellow stator wires)?  If so, a dirty fuel filter can be your problem.  You have one stator winding that supplies electricity for running the engine, including the fuel pump.  The other winding supplies power for lights, etc.  When the fuel filter gets dirty, fuel pump amp draw increases, overburdening the system.

[triangleforge]

Right on both counts -- it's a single phase system, and a dirty fuel filter can be the last straw in an electrical system that lives on the edge in the best of times...

Thanks, Howie!