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Very strange spark issue!

So I jumped the voltage regulator and unfortunately the charging light did not go out. What would the next step be? Diode board? My understanding is that an open rotor results in no light. Is that true? The brushes looked OK to me, but I didn't do any scientific tests on them

I think the purpose of jumping the regulator was to find out if there was a voltage increase when doing so. If the regulator is at fault, I believe the voltage will increase dramatically when the engine is revved. If it didn't increase, then you definitely have an alternator problem. Time to methodically go through the above links.
 
There was no increase in Volts at the battery terminals. So it's definitely a charging issue. Again, it was my understanding that an open rotor would show as NO charging light. Can anyone confirm this? Also, I don't believe I mentioned it; the bike is a 76 R75
 
There was no increase in Volts at the battery terminals. So it's definitely a charging issue. Again, it was my understanding that an open rotor would show as NO charging light. Can anyone confirm this? Also, I don't believe I mentioned it; the bike is a 76 R75

Indeed, an open rotor will not allow the light to light. The bulb is in series with the rotor so if the rotor is open there is no path to ground through the bulb.
 
Ok, so that leaves what? A closer inspection of the brushes? The wires connecting the stator to the diode board or the diode board itself. I mentioned that I did have the board out. It looked OK, no melted soldering or cracks but I suppose they can still go bad. I'm not giving up yet, I'm just getting this sinking feeling that I have some strange issue that's going to be a nightmare to figure out.
 
.............
I also think Oak's top end manual should be near your toolbox too and used every time you need to pull the heads. It's very well written and easy enough to follow along and avoid common mistakes. Oak has sadly passed away but I believe his top end book is still available from his wife. Sorry I can't seem to find her contact info but searching here for "Oak top end" should yield results.

I requested this info in a recent thread. I also noticed in the most recent issue of "Airmail" the ABC monthly, that Oak's column is continuing publication. This is because he provided many months of technical advice to the readers. In the Airtech column, they provide the info to order Oak's Top End Manual. Order goes to his wife, Carol Okleshen. $30.
22637 Ridgeway Ave
Richton Park, IL 60471

I ordered a copy a week ago. Nothing yet.
 
Ok, so that leaves what? A closer inspection of the brushes? The wires connecting the stator to the diode board or the diode board itself. I mentioned that I did have the board out. It looked OK, no melted soldering or cracks but I suppose they can still go bad. I'm not giving up yet, I'm just getting this sinking feeling that I have some strange issue that's going to be a nightmare to figure out.

Well, as Paul just stated if the rotor is open the charge light will go out. If it's flaky you will see dim, intermittent and other odd behaviour of the light. The easiest way I know to test it is to simple lift up the brushes and slip a match book cover or other small thin piece of cardboard or plastic under the brushes so they are no longer contacting the slip rings on the rotor.

Then take your meter set on OHMS and measure the resistance of the rotor by touching the leads to the two slip rings. If you get NOTHING or OPEN then the rotor is no good, Get a new one from EuroMotoElectrik or Rick at Motorrad Electrik. You will need the special bolt to get it off.

Inspect the brushes closely while you are in there. Next to the rotor which is probably the number one failure to charge culprit the brushes being worn out and not making proper contact becasue they are simply too short to reach the slip rings anymore is probably number two.

I would still not rule out some corroded wiring hiding somewhere. The connector on the BACK of the diode board (the one you cannot see till you remove the diode board) is also a well hidden culprit in charging issues. I think Greg Hutchison mentioned this recently as well...

Use Kurt's links and be methodical starting at the rotor and keep a running list of what you've looked at. You'll find the problem. I'm still not ruling out the regulator...
 
With the brushes lifted and matchbook cover isolating them, if you put a penny across the slip rings (only touch the two slip rings) and see if the gen lamp lights up, the rotor is bad. Snowbum has a thorough discussion of all tests.
 
With the brushes lifted and matchbook cover isolating them, if you put a penny across the slip rings (only touch the two slip rings) and see if the gen lamp lights up, the rotor is bad. Snowbum has a thorough discussion of all tests.

Yeah that works but I like to isolate one thing at a time. The penny test relies on the wiring and bulb connections to be good in order for the light to work. The ohm meter simply tests continuity of the winding. And we know from lots of failures that when there is no continuity the rotor has an issue of either a dead short from melted insulation or it is open due to wire breakage somewhere in the winding.

The owner does seem to have a working bulb in this case so the penny test should work.
 
MJM -

You're correct. The whole idea is a thoughtful process of working through the system until the problem is revealed. That's what's so good about Motorrad Elektrik's book...that's the way it is designed.
 
I'm blown away by you folks taking time to help a fella out. Ok i've got the bike apart right now and I think I may have found the issue! My rotor is showing open. There's no ohms coming up on my multimeter. But going back to an earlier question, how is it that I'm still getting a gen light? Is there any conceivable way that these bikes can have a bad rotor and a gen light on?
 
follow up question... is there anyway to mess a rotor test up? I've got my meter set to both 200 and 2k Ohms both with no change. That would seem to indicate an open rotor correct?
 
I'm blown away by you folks taking time to help a fella out. Ok i've got the bike apart right now and I think I may have found the issue! My rotor is showing open. There's no ohms coming up on my multimeter. But going back to an earlier question, how is it that I'm still getting a gen light? Is there any conceivable way that these bikes can have a bad rotor and a gen light on?

The only time I have seen that was when the rotor was temperature sensitive and would show OK cold and open hot. The other way it can happen - discovered after 3 days in a sheep barn at the National rally in Lima, Ohio, is if the wires at the alternator brush connections are mis-connected. The brown must connect to the ground brush and the blue or black must connect to the hot brush. Check this!

If reversed the circuit through the bulb is connected directly to ground but not through the rotor.

Thanks Oak (RIP) for helping me fix this on Leland Prothe's bike.
 
Well now I'm a bit dejected. I'm almost certain my meter is working correctly, and I'm very certain my charging light is on. So what gives? My brushes haven't been off since I've owned the bike and they're showing nearly 9mm exposed from the housing
 
Since Oak's Top End Manual was mentioned earlier in this thread, I'll update that I received my copy of the manual in today's mail. So, Carol Okleshen (or someone in the family) is still filling those orders.
 
The very worst rotor failure I've had to diagnose is one in which the rotor opened only when at speed, but regained continuity when slowed down.:banghead
 
follow up question... is there anyway to mess a rotor test up? I've got my meter set to both 200 and 2k Ohms both with no change. That would seem to indicate an open rotor correct?
Normal rotor DC resistance will be on the order of maybe 10 to 30 ohms. Your 200 ohm scale should show that. Assuming DVM is displaying full scale (200+) ohms means the rotor is open.:violin
 
Hey stuff happens. I've checked every piece of the of the charging system based on tips from from the good folks on here and the rest of the knowledge on the web. Everything seems fine besides my rotor that appears to be open. Just looking at it, indicates that it may even be original 64K. Plenty of rust on the housing and some cracking of the sealant they used on the copper. I guess I'll be making a call to Rick on Monday. I'm still bothered by the fact that I did have a charging light at all time, but snowbum does list an open rotor as a likely cause of a full time charging light.
 
Hey stuff happens. I've checked every piece of the of the charging system based on tips from from the good folks on here and the rest of the knowledge on the web. Everything seems fine besides my rotor that appears to be open. Just looking at it, indicates that it may even be original 64K. Plenty of rust on the housing and some cracking of the sealant they used on the copper. I guess I'll be making a call to Rick on Monday. I'm still bothered by the fact that I did have a charging light at all time, but snowbum does list an open rotor as a likely cause of a full time charging light.

The circuit that turns the gen light on is not typical at all. It is very cleverly designed that will light the bulb if the voltage is too low on _either_ side of the bulb. The first time I tried to wrap my electronics tech brain around this I said that's impossible. Then I looked at the circuit for quite some time and read Snowbum's section on it and the way they did it is actually brilliant. So yes, it is possible that the bulb goes on with an open rotor.

You see, the trick is that the bulb does not care if current flows one way or the other so in order for the light to go OUT the voltage on both terminals of the bulb must be EQUAL. That's a huge clue into understanding how it works. Now just go stare at the schematic for an hour like I had to until the bulb in my brain turned on. :lol
 
If the rotor windings are shorted to ground it is possible to have the current illuminate the bulb and at the same time lack continuity from slip ring to slip ring. Try testing continuity from the hot brush to ground with just the ground brush isolated from the rotor with a business card or similar.
 
As others have said, vibration can cause all sorts of problems with electrical circuits, including those you are having. Often the only way to fully troubleshoot the issue is to replace the suspect part and see what happens.

Wayne
 
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