I started having this problem yesterday. I took a fairly long ride on my bike and about 2 hours in I felt a loss of power and uneven power. In fact, I first noticed because I stalled it twice at a traffic light. After sitting for a few minutes it was fine and got me ~3 miles from my home when it completely crapped out and I ended up walking the bike home, fun stuff.

So when I got home the battery was registering in at 9v. So I charged it over night. Today I went for a ride and it started happening again, I wisely stayed close to home. So I got home and ran a quick test. I checked the voltage coming from the alternator at idle and 5k RPM and register ~14.5v, this appears to be within spec. So signs are pointing to the regulator. I went to check the diodes and got some odd results, but I am not 100% certain I did it right. So I read up another way is check for AC voltage across the battery terminals and if there's more than 3-4v AC the rectifier is bad--mine dialed in at 27v.

I just wanted to run this by someone for a second opinion before I throw in the towel and replace the rectifier. Thanks!

 

hmm, this could be the sudden "engine freeze up" that you mentioned in the other thread. The electrical dropping out while riding.

 

So I replaced the rectifier to no avail... I'm starting to think my 4 month old battery w/ ~500 miles on it might be damaged... I'm going to get it load tested this weekend.

 

Could be an erratic voltage regulator? (I've never known a regulator to just "die." They always seem to go high, then go low, etc.) A regulator is different than a rectifier, btw. If the regulator is wacked, it can affect other things in the food chain and make you think the problem is something it's not.
Caveat: I may be wrong.

 

The rectifier is a rectifier/regulator. It has the circuitry for a rectifier (AC->DC) and also the diodes in there to handle the voltage regulation. So in the end I ended up replacing both. :/

 

Double and triple check your grounds and cut-off switches. If you've replaced all that stuff and still having problems.....hmmmm. Battery only 4 mos old?? Guessing you put slowwwww initial charge on it as spec'd?

 

Yeah, I should double check my grounds for sure. I didn't do that yet. I brought the battery up on a slow 2amp charge.

 

Shouldn't be your battery then. Too many guys get impatient on initial battery charge, then can't figure out why it doesn't hold juice. Good job!

 

Is the battery still being drained, or is it still dieing while maintaining the charge? If you are getting proper voltage to the battery I cant imagine any real problem with the charging system, and any grounds or wireing issues should kill the bike without draining the battery significantly. If the battery is not recharging after everything tests out you got me, but if the battery is holding a charge I would move on to ignition system.

 

Thanks for all the great advice guys. I had the load test done and it did indeed fail. I bought a new battery yesterday, filled the acid up and it had finished charging last night before I went to bed. I'll probably get a chance to test things out tomorrow. I'm still surprised that such a new battery could fail in such a short period of time.