Bad regulator? I have a 2002 Daytona Centennial Edition. I think I might have a bad regulator. I left the key on and the battery ran dead. I charged it and the bike was still dying, so I replaced it. The new one is in and the bike is still dying, leaving me to believe it's a bad regulator. I'm taking the new battery back for testing, but my question is. How to I test the regulator to tell if it's bad? So, I didn't get a chance to test the new battery because the shop closed. But I called the local dealer and talked to him for a minute about the regulator. He mentioned that the regulator/alternator should put out a little more voltage than the battery at about 2k rpm and that's a good way to check. I plug the meter in with the bike turned off(battery's been on the trickle charger for a bit), it's sitting at a little over 12v. I start the bike up and check the voltage, 11.85v or so. I rev the motor up, no change, in fact, the voltage is dropping as it idles, 11.84, 11.83 etc. So, I'm pretty sure it's the regulator. Last ditch effort, I check the fuses. I find a bad one, fuse #2(ignition switch 30A). I look around my garage and I find the largest fuse I have laying around, 20A. I throw that one in there, start the bike up, it blows. Not sure what that's all about, I'll run get a few 30A's so I can try one of those. Why would I be blowing the ignition switch fuse? BTW, the bike will still start with the blown fuse in there. Any ideas?

Fuse 2 is actually the fuse from the regulator to the battery (see schematic below) - so if it's blown then you are not charging the battery. Put the correct fuse in - if it blows again, you may have a shorted regulator. Unplug both connections to the regulator: With your test meter set to 'ohms' check in turn between each of the three yellow wires in the 3-pin connector to both the red & blacks in the 4 pin connector (the two reds are already connected to each other, as are the two blacks). Also check between the reds & the blacks. None of these should readings be 'short' (zero ohms). Inspect the wiring at the three-pin connector - if the bike's harness looks charred/burned that is a sign the regulator has shorted. There is possibility it could have taken the stator with it. Incidentally, the cable that plugs into the three pin connector - that should be a replacement auxiliarry harness: the original was deemed too small gauge for the job & was replaced with the auxiliary one as a recall. You should find that cable is stand-alone from the main bike harness and you can follow it back to the stator output connection. At both ends you should find the connectors of the original harness that is 'laced' into the complete harness. If you do not find that auxiliary harness, you need to get it. You should be able to get it at no charge from Triumph if the records on your VIN show it was never supplied.

Fuse # 2 is indeed the fuse between the R/R output and the battery (and system load) 20A is too small. The term 'ignition' is misleading in this instance. 
It MUST be 30A - that fuse carries ALL the power to the bike, not just the charging current. When the R/R output exceeds the battery voltage, current flows into the battery, not out of. 
The reason the voltage is dropping is because the R/R is not inputting any current to the system because of the blown fuse and the battery is operating in 'total loss' mode. It will continue to run until drained beyond the point of being able to sustain operation. 
The Regulators and Stators both are common failures on the Triumph - use my personally authored diagnostic guide (already referenced in another respondent's solution below - http://www.triumphrat.net/speed-triple-forum/104504-charging-system-diagnostics-rectifier-regulator-upgrade.html) to determine if there is a problem with either component. Note also in that same guide that the three-terminal connectors between the stator and R/R are subject to deterioration - there are two on the Triumph, one close to the R/R and one close to the Stator - inspect those and replace as appropriate. 

There is a recall on the regulator cable. It corrodes badly where it connect to the regulator. Can fry your alternator wiring. Also my regulator went bad too. Look into the upgrade mod for the regulator. The stock regulator runs too hot and there is a more efficent regulator that people have been swapping out to. It runs cooler and get the battery charged way better than the stock regulator. Spark to the plugs also improve.