Intermittent Charging Issue (really long sorry)

[pkovo]

I recently had a post on here about replacing my regulator and rectifier. I replaced my regulator with the VR115 with relay and replaced my stock rectifier with one off EBAY. In the process, I found and fixed some bad connections, I cleaned and replaced many connections, replaced both battery cables, replaced battery, and cleaned ignition and kill switch contacts. Rewired all inline fuses.

So after this, the bike was charging great. 12.5 at idle, 14.35 at 2k plus RPM. Very solid and predictable. I've had it out for a few rides, all relatively short (20-40 miles). I don't yet have a voltmeter installed on the bike, but I've checked it at the end of each ride, and the battery has been fully charged each time, and the system is spitting out the 14.3 volts. All was well....until today.

Worked from home, so I went for a spin at lunch. Maybe 30 miles. When I got home, the bike's idle was a little "off". Just not as steady as it has been. It's been rock steady at 1250 RPM. shut it down and checked battery voltage, and it was a touch lower than it's been. Started it back up, and the alternator was pulling out a full volt lower than it has been, and just didn't seem as responsive to throttle input. When I held the revs at 3k, the voltage was in the low 13's, and steadily climbing very slowly. Normally it just goes right up to 14.3 volts or so. Since I was on lunch break, I threw the battery on my tender, and had to walk away from it.

Just finished work. battery topped off. Started it, and it's back to normal. revs above 2k, and it's around 14.3-14.35 volts.

As time permits, I'll go through the connections I've recently done, and make sure all is well there. I'll also look further on existing connections, because although I checked a lot, I didn't go through everything. But this whole thing got me thinking. I've used this bike very little over the past decade. I started having charging issues with it probably right around 10-12 years ago. Back then we figured out the rotor was bad, replaced it, and the charging was back. However it was never exactly right after that. It woudl be weak, then i would adjust that Original voltage regulator, then my battery would boil, and I never gave it enough attention to really get to the root of the issue.

So long story short, the charging guide says something like "don't stop when you find one thing wrong, because there may be several things wrong" well, I think I stopped searching too soon. Now I know my VR and Rectifier are good, but I think I have an intermittent problem, that shows itself when the bike is warmed up. I think I always thought I was fixing it, by tweaking my regulator, or by cleaning connections, but in reality, I think it was just an intermittent problem, and it would stop showing itself so then I'd call it good.

If there is something that jumps out as obvious, that some of you experts can think of that I should check first, let me know. Otherwise I'm back to checking connections, and then going through all the steps in the guide and checking everything with a meter.

One thing that popped in my head is the stator. It's 36 years old, so certainly wouldn't be a surprise if it's failing. I was thinking if the insulation is broken down, it might fail when it gets hot but be OK once it had cooled.

My initial thought when I pulled this thing out of storage recently was to jump right into a PMA. I may end up going that route, but I don't want to until I've exhausted all reasonable possibilities. I also don't want to go that route to cover up some potential wiring issue I could have.

Anyway, if anyone is still left reading this novel of a post, and has some things I should check first. I'm all ears.

 

[Vlad]

I think the stator is three phase, so a partial drop in voltage might indicate one of the phase windings bad or one of the diodes in the rectifier have failed (unlikely since that's new though). Also, a lower, non-zero rotor voltage would cause a partial drop in charging voltage since the voltage induced in the stator would be lower due to lower rotor current. But these are all just hunches.

I would definitely start by checking the resistance of the rotor and stator with an ohm meter/multimeter, check the rotor brush length, and carefully clean the rotor slip rings (is that what they're called?) with some fine sandpaper if they're dirty. While you're in there, check all of the connections too. Good luck!

 

[TwoManyXS1Bs]

Just a coupla thoughts.

I'd go thru the brush block. Remove it, clean, check connectors, clean screwheads, ...etc.

If the relay powering your regulator isn't vibration-isolated, its points may bounce and create temporary poor connectivity from arcing. Can you open it up for inspection and service?

 

[XSLeo]

I have a rotor that ohms out ok cold but changes as it warms up. The resistance goes up. To around 8.5 ohms when hot. Ride your bike till warmed up and quickly do an ohms check on the rotor. If it is higher than it should be this may be your issue. Testing the stator cold and hot may reveal an issue there too.
Leo

 

[Vlad]

^brilliant

 

[angus67]

I have a rotor that ohms out ok cold but changes as it warms up. The resistance goes up. To around 8.5 ohms when hot. Ride your bike till warmed up and quickly do an ohms check on the rotor. If it is higher than it should be this may be your issue. Testing the stator cold and hot may reveal an issue there too.
Leo

brilliant, indeed. I just put a vr-115 on my 71, and although the original was working fine, charging at 14.2 volts @ 2500rpms, the vr-115 is at 13.5(+-) @2500 rpm. I read some have a relay for the regulator? why?
I also noticed the insulation on my rotor looks a little cooked. Cold, it tests at 5.0 ohms, but now reading I should check immediately after running, might just be too high of ohms.
Why would a just a swap to a vr-115 into a working system be so low? Let me guesse,,...check grounds.

 

[pkovo]

Thanks all. I just checked all my new connections and they all looked good. I checked my brushes a few weeks back. They were within spec but one was getting close, so I just soldered up a new one.

My relay is rubber mounted. I got the idea from Pamco Pete, but since he mentioned it, I noticed MikesXS sells them, aerostich sells them. It's a basic automotive relay and seems popular on bikes when guys are mounting accessories. I don't think it's the issue but I can bypass it if/as needed. I used it to cure a slightly high charging voltage. Normally the brown wire feeds the voltage regulator and it's under load. The Voltage regulator uses this as it's reference. In my case, I had a slight voltage drop on the brown wire since it was under load. With the relay, the brown wire essentially just turns on the relay, and the relay then feeds a fused direct line from the battery. For me this means when all is working properly I get a max voltage of 14.35 with the relay instead of around 14.65 without it.

The rotor is an interesting thought. Would hate to think its shot, it's got under 2k miles on it, but definitely a test I'll do. I can test that pretty quickly when the condition present itself, because I have no idea how quick it "recovers" and goes back to normal. I plan to do the same with the stator, but I might not be able to test it as quickly when it's warmed. I need to get a voltmeter installed so I can clearly see what's going on when I'm riding.

I've pretty much resigned to the fact that if I have to shell out for another major part on the charging system (stator or rotor) I'll likely just go with a PMA kit. Regardless, I would still like to be certain of the issues I have even if I go that route.

 

[pkovo]

Just thought I would post an update...just because I hate when threads dead end. After my last post I went over the brush block. Soldered up an old brush I had that was longer than my short one. Even though it was in spec It was getting short so thought I would eliminate it as a potential issue.

Stator and rotor both pass tests cold., no surprise. Went over all the wiring for the stator. It looked good, but I took apart the connector that's hard to reach Up behind the top of the carb. The connectors didn't look bad but I wanted to clean them up. Here's where it gets interesting. One of the male connectors for one of the three legs of the stator wasn't "locked" into the terminal block. However, I don't know if it was like that from the start, or if I knocked it loose when I was probing with the meter. If it was like that from the start, I'm thinking theoretically, it could have been intermittently losing connection perhaps from vibrations, hitting a bump, etc.. Maybe a stretch but hey, you never know.

Anyway, I quit there. Got one 30 mile ride in after this with my voltmeter and watched it like an obsessed weirdo. When I started I know the battery wasn't topped off. It was charging at 14.4 solidly for first 5 miles, then dropped to 14.3, then 14.2 by end of ride. Put it on the battery tender and a few days later took a ride about 70 miles. This time it settled in at 14-14.1 the whole ride.

I resigned to call it good for now, until/unless it shows a drop again, and focused my attention to carburetor issues on another bike. However, During this stretch I've obtained many of he pieces needed for a PMA swap at discount prices off EBay, just in case my rotor or stator do quit on me. I'll just shelf them until that day comes. Hopefully not any time soon. If it starts to fail on me, I'll try and test toe rotor and stator as quick as possible to see if I can pinpoint what's failing.

 

[XSLeo]

You replaced one suspect brush with another old brush?
That may be ok. Not only does the carbon part of the brush wear but the spring does too. As springs age they gert weak. This can reduce the pressure of the brush on the rotor slip rings. This would lessen the contact between the two. This would reduce the availible current flow through the rotor. I might replace your old brushes with new. At least get them, then you will have them if the charging gets weak.
Leo

 

[pkovo]

You replaced one suspect brush with another old brush?
That may be ok. Not only does the carbon part of the brush wear but the spring does too. As springs age they gert weak. This can reduce the pressure of the brush on the rotor slip rings. This would lessen the contact between the two. This would reduce the availible current flow through the rotor. I might replace your old brushes with new. At least get them, then you will have them if the charging gets weak.
Leo

Yeah, that's pretty much what I did. The brushes wear uneven and I replace them in pairs when the short one is close to too short. I took the long one from my last pair, clipped it and soldered it to the other holder. That spring could be worn, but I'm banking on the longer brush keeping it compressed enough so it's under more tension

New ones are needed, but I'd like to confirm I don't have bigger issues with this setup before I buy them. And I have to get my list of needed odds and ends together before I do a mikesxs order.