The patient is a '92 R100GS that I finally put back together after being apart since 2008. It fired right up and the tranny I messed with seems to shift OK, but I'm not getting a healthy charge. I put in a new battery and charged it, but even when I rev it to 4000 RPM I'm barely getting 13 volts charge at the battery. Tried swapping in a used good regulator from my airhead parts bin and saw little improvement. Brushes and all connections look OK. Is this normal airhead anemic alternator output, or is something wrong? thanks in advance, Diana
I get over 14 volts on my R80G/S at 4K rpm..... this was after I changed out a regulator. The old one maxed out at about 13.3 volts.
It could be a bad battery. Load test it. How far does the voltage drop while the starter is cranking? Yes, new batt's are often no good. Good batt? A TUNED setup should get you between 13.8 and just under 14. What to tune? That's a long story!
It sometimes help to 'electro-shock' the rotor. Connect a piece of wire to the + on the battery, start the engine and stroke the + side of the rotor with the loose end of the wire. This will help the magnetic field in the rotor going. Paul.
:whoa what? I've never heard anything like this. Make sure your grounds are nice and clean. It could very well be a bad new battery. BUT If you put a jumper wire in between the two sidebyside connectors on the voltage regulator harness connector and start up the bike, your voltage at the battery should jump to 15 or 16+ if everything else is working. No change when you swap a new one in says to me the VR is fine. WHat does you charge light on the dashboard do when you turn the key on, start it, and then rev it? ANother thing I would do is take the DF connector off the alternator and touch it to the alternator housing (key on, but bike off.) This Should light up the charge light. If not, we'll know a little better where to look, or not bother looking as the case may be. GOd I love charging threads :lol
Recharging generator fields: http://www.doityourself.com/forum/o...ngines/188605-recharging-generator-field.html
But we are working on an alt. that does does not have permanent magnets but has an electromagnetic field. Big Diff!
The rotor theoretically gets it's charge from the battery, but it probably retains a little eesidual charge, no?
I get more than a little nervous about "arcing" when there's semiconductors around, so I won't try that... Last I remember "arcing" was with a generator on a really old car! I think I'll charge the battery again just to make sure it has a full charge, and check the voltage drop as loads are applied to make sure it doesn't just have a surface charge. The idiot light is working properly, so that's not the problem. I've got a whole airhead spare charging system from when I put an Enduralast system on my ST, so I think I'll try the regulator for that system and if that doesn't work I'll check and clean all the connections. Thanks again, and more advice is welcome!
If you are getting less than 1 volt increase in system voltage measured at the battery terminals with the engine off and it running at 3000 RPM the low charge output could be due to just a little looseness or corrosion at one of the numerous terminal connections or a diode board with one or two diodes gone bad in it. The best resource I have on charging problems is the Classic Boxer Charging book from Ricks Motorrad Elektrik. If the system worked OK two years ago and now doesn't I would start by cleaning and tightening all the terminals.
It is not as scary as it may seem. The regulator does the same, switching power on/off to the positive brush. By elektro shock you do the same, only bypassing the whole wiring and re-activating a lame rotor. Paul.
Charged it up good, showed 12.8 volts no load. Started up and was giving 13.5 volts charge @ 3000 RPM right away. After a couple more starts was back to 13 volts max @ 4000 RPM. I'm beginning to suspect the battery, if this keeps up I'll take it back to the farm store (purists be damned, it's a garden tractor battery, available just about anywhere). Tried a couple other known good regulators with about the same results. Could be that the "newfangled" charger with all the LEDs is screwing up, I prefer the "old school" ones with a meter.
Sounds like in the spring it is time for a new battery. Be sure that all the connections and grounds are clean and tight. To check the voltage regulator, unplug the voltage regulator and jumper the bottom two of the connections. Start the bike and check the voltage at the battery, you should see around 15 VDC, don't run it long just long enough to check. Also check the voltage from the B+ (large spade) terminal on the diode board to ground and the battery + terminal to ground. The voltage should be the same, if not check from the + starter lug to to ground. You could have a high resistance in the wire from the diode board to the starter or a dirty lug on the starter.
The battery really has little do with this problem as described. When engine is spinning and the charge system is up to snuff it will drive the voltage 1 to 1.5 volts over the at-rest voltage of the battery... One. Does the charge light come on with the ignition on but engine off? Yes? Go to Two. No? - check the rotor for continuity. One and one half. Start engine and rev over 1500 RPM. Did the charge light go out but still weak output measured at the battery? Check the light for glowing so softly it can't be seen in the daylight. Have to check at night or in a dark garage. Charge light glowing brightly or still faintly? Go to Two. Two. Does it go out when the engine is turning more than 1500 RPM or so? No? Or burns half brightness over 1500 RPM? Check voltage regulator. Do this by removing gas tank and locating the regulator. Pull the wiring plug connector out of the bottom of it. Take a piece of wire and jump the DF and D+ wires. They are black and blue.wires. Start engine and rev to 2000 RPM. If the charge light goes out the voltage regulator is bad. If the charge light continues to burn the problem lies in the rotor, stator, or diode board. (most likely the latter) Three. Disconnect the battery positive cable. Remove front cover then reconnect battery positive. Check diode board ground. A 92 might still have the four rubber mounts. If two break the diode board touches the front cover and the board is toasted. If the mounts are good check the brown wires that may have been added as extra grounds. Solid mounts are the way to go. Check the heavy red wire that connects to the B+ terminal on the left lower corner. Burnt or crispy? Or green and powdery? Corrosion here causes massive voltage drop. So does the heat that crisps the wire. Check voltage drop by checking the battery voltage at B+ and the battery negative. A drop of more than .5 volt here is not acceptable. Got to check the other end of the red wire at the starter terminal. If looking good so far you can test the individual diodes with a multimeter but if you have another known good board there you go. If the red wire has seen better days replace it, probably replace it anyway - it is cheap and twenty years old. Replace the brown ground wires with a single heavy 12 gauge one grounded to the left side bolt holding the starter in place. On the back of the board is three wires and terminals, the D+ ones. Check for the same corrosion or heat damage as the red B+ wire. I think by now you will have found your problem.
Here's another thought, after sitting for long periods copper based slip rings (as on the rotor) can and do form a kind of oxide on the surface. This can cause the brushes to not make good contact and result in low or no voltage to be produced when the unit is used again. The slip rings can be cleaned by scrubbing with an abrasive material (common tool in the dc electrical machine industry). An old typewriter eraser can be used instead of the expensive tool to gently remove this oxidation. The symptoms you describe and the improved voltage each time the unit has been run suggest this may be the situation.
