taillight flickering

mdiorio said:

tested that it was charging 13.5 volts... <snip> I had to replace the battery and Regulator late last year as the old one failed and over charged and melted the battery.

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Shovel_Dan78 said:

When you checked the charging, did the voltage go up with rpm? When I first got my bike, it was reading 13v, so i thought it was ok at first. After testing it later on, it wouldn't go up when I revved it, because the regulator was toast and I was just seeing battery voltage (which was 13v, fresh off a tender).

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Hi.

So, I'm a real curmudgeonly fuckhead, so take that for whatever it's worth before you get pissed off at my reply, but also keep in mind I just sat down to write a response that took half an hour, so weigh that with my fuckheadedness.

For starts, I don't like all these quotes above, because I don't think the manual lists that shit as the right way to test these systems. Yeah, it's fine for a quick-and-dirty check on an obvious system fault and I do it myself at times, but this is not the prescribed method of testing. I am a pretty big believer in testing things because... well, because it fucking works, and because I like to know shit is bad before I start buying crap, because then I have money for beer.

This voltage check and all is nice, but it's checking complete system voltage, not the individual components that make up your system (some of which are not tasked with producing 12VDC current).

I personally would start by identifying what charging system was in this machine. Is it the stock 1971 setup, or something later? That will net you the specs you need for proper testing—you can't test things without knowing the specs. You can usually tell this by the pin pattern in the stator and reg.

Next, your battery should be load tested on its own. No further testing can be trusted without a known good battery. Since yours is fairly fresh, if you want to assume that is good, I'm game, but technically a voltage check is not really the way to test it. But like I said... we can proceed if you don't mind not knowing or don't have a load tester. (Your local auto parts store does, and they will probably load test your battery and charge it for free if you ask nicely.)

After that, I'd look to test the reg. I mean...we know you recently put a reg in this old girl. 13.5 volts at idle sounds reasonable to me; what does your manual give for specs for the charging system you have? Do we have a good ground path there? It would be prudent to do a quick check for continuity between frame and reg body, and then if that passes you can shoot the moon and test for resistance. Shit, as long as your DVOM is on those settings, maybe it would make sense to check the ground path to the battery, too, for both continuity and resistance.

Where I am getting concerned is in your replacement of the VR without hearing mention of performing the correct test sequence for the stator. Hear me out: you know you had a melted battery, and then you got (I'm assuming) some big fat number on the VR, like 15 volts, and said, "Fuck, this thing failed and wiped out my battery. Better replace both." Remember I said I'm a big believer in testing things? I'm also a big believer in the idea that when a problem crops up on a system you just worked on, odds are excellent your problem can be found there. Correlation and causation and all that. A VR can fail by overcharging or undercharging, of course, but a VR that fails (or a battery that melted, yikes!) can also place such a tremendous load upon the stator that it can be destroyed.

We know for a fact your stator was working like a rented mule when that VR failed, right? Did that cook off, too? Normally you'd test stator output by removing the VR plug, switching your meter to AC, and testing the output at several spots in the rev range. The exact speeds and outputs will vary based on the charging system you've installed in the motorcycle, which is why I led with that (and would recommend you crack the manual of a motorcycle that uses that system, so you can get the specs).

Most of the shitty old systems have been updated to later Shovel or even Evo specs, which actually can create its own set of problems... if you have a great big 22A or 32A system set up in a bike that has chopper-esque lighting, you're shunting a lot of current to ground, heating up the VR, and basically making the whole system work pretty hard. Burning a headlight all the time can really help with that. Or you could try putting a totally boss eight track in the fairing.

In any event, I would like to see you maybe isolate that stator and test it, running the bike off the battery which we believe to be good. That way, we could isolate the flicker to the wiring/ground instead of the electricity providin' bits. If it only flickers when it's running, that might just support my theory here, though that it is the electricity-providin' bits.