Hey everyone. If you can't tell I'm new here. I have a 1981 R100RS and I love it. However, yesterday it died on me. I had a friend come jump it and we were able to ride most of the way home, about 6 or 7 miles, but then it died on the road again. The friend I was riding with said he could see my headlight getting dimmer and dimmer. So we brought it back to his garage and put the battery charger on it. Late last night we started it up and put the voltmeter on the battery while it was running. It just stayed steady at 12.5 volts even when reving. So that's telling me it's not getting any charge. Am I right on that? Forgive me, I'm a little new at this, but I want to learn. Anyway, I took the front engine cover off to take a look at the altenator and the diode board. To me it looks awfully dirty in there. I'm hoping the altenator brushes are just dirty and not making good contact and hopefully just need a good cleaning. I'm attaching pictures of both and I'd love to get your feedback. Also, if you could guide me to any good ways of testing this so that I can narrow it down, I'd greatly appreciate it. Thanks for the help. I apologize if this isn't in the right forum.
Ok Usually you have to disconnet the battery for front of motor work
you have a Thunderchild Dieode replacemnt that looks like you advided the usual short on orginal part
you still may have a thunderchild problem besides a dirty front of motor how long have you had this Barn Fresh find of a bike?
A unchecked unknown bike can kill you.
and maybe you better do the whole tomato find a Airhead Guru to help point you where to go, find his vise keep him well stocked and you will win................................................
Lyman's right, always disconnect the battery before removing the front cover, or you risk shorting the diode board and Bad Things Happen. Does the charge light come on when you turn on the ignition? It should, and the charging system won't work without it. It could be an open circuit in the rotor itself. To check, lay a penny across the two contact strips and see if the light comes on, ignition on, engine not running. If it doesn't, it could just be a burnt bulb in the instrument cluster(cheap fix) or your brushes are worn or making bad contact. The two strips where the brushes touch should be bright clean metal, you can rub them clean with a green Scotchbrite, or similar pad, while the engine is running (another cheap fix). Do not use sandpaper or emery cloth to do this! Get back to us when you have covered these basics...
Welcome aboard. It's not surgical clean in there, but for an older bike it doesn't look too bad.
Have a read thru the link...it's a sort of collective experience here, when charging problems happen.
Firstly though, has the GEN idiot light on the instruments been working correctly? ie bright when ignition on, engine off. Bright at idle, off as rpm rises above 1500 rpm or so?
Oh, a picture of your bike is always a good thing. It helps put a face to the poster!
Does it look like the forward snail spring has bottomed out on the brush holder? If so, then the brushes could be severly worn and not getting the pressure from the spring to provide good contact.
Did anybody mention bridging the voltage regulator to see if it is the culpret? I had mine fail in such a way that it would not pass any charging current at all, whereas when I bipassed it I got a reading of about 16 volts (briefly!) at the battery. All I needed was a new regulator.
Kurt in S.A. wrote:Does it look like the forward snail spring has bottomed out on the brush holder? If so, then the brushes could be severly worn and not getting the pressure from the spring to provide good contact.
Kurt in S.A.
Agree with Kurt. Even if the worn brushes are not the entire problem, now's a good time to replace them. With engine revs up, a VOM on the battery terminals should read close to 14V. How old is the battery? Clean terminals and connections throughout are critical -especially ground/earth terminals. Clean and when possible a light smear of dielectric grease.
A jumper wire taking the VR out of the circuit can assist in determining the regulator's health.
It's an Airhead. The fix will be something simple. The trick is locating that simple fix
Your electrical system looks nice and fresh with fairly new leads, possibly fitted when the Thunderchild diode board was fitted, I had one fitted and it lasted well.
The New Diode board as fitted as part of the 450W alternator is a real Killer for shorting out the positive connection when removing the outer cover.
Also remember that 95% of all electrical problems on Airheads arise from corrosion in the thick red wire and its connectors at the starter Relay.
Charles
Replica 1070 R90/S (based on 82 RT)
1975 R90/6
Wow, tons of great responses here. Thanks guys. I do not get a GEN light at all. I took apart the cluster and tested the bulb and it's good so that's not the problem. I'm going to try that penny trick suggested. I also did order a replacement rotor hoping/thinking/assuming that's the problem.
