Odd GEN Light

Right now I'm stumped on this. Bike is a 1984 R100. It has a 4 year old Enduralast II alternator kit.

Close to the end of a ride, I stopped for gas. When I restarted the bike, the Gen light was off. But, a block or two of riding and the Gen light was working normally, coming on at idle and off with higher RPM. When stopped at home, turned ignition on and Gen light was off.

Next ride, Gen light was working at the start. But, same issue occurred later. After running for a while, Gen light didn't light up after stopping, but started working correctly after a couple of hundred feet.

So far I have replaced the voltage regulator and put a dvm on the diode board and rotor. The rotor measures 6.2 ohms which EME says is in range for this rotor. Tested the diodes and they all were okay for only passing current in one direction.

Seems like an intermittent rotor problem. Do I just keep riding until something fails hard?

Any other suggestions for figuring this out?

I would take apart the gauge cluster and clean the terminals, that charging light wiring goes through many terminations and they all must be spotless. Cleaning that up is a fun easy job on the bench in a well lit place. I did mine about 6/7 times in the 32 years I owned a 84 just for PM and cleaning the glass of the gauges. Usually that light starts to give hints that something is amiss at night, when the rider can see a dim red at low rpm. Good luck.

Right now I'm stumped on this. Bike is a 1984 R100. It has a 4 year old Enduralast II alternator kit.

 

Close to the end of a ride, I stopped for gas. When I restarted the bike, the Gen light was off. But, a block or two of riding and the Gen light was working normally, coming on at idle and off with higher RPM. When stopped at home, turned ignition on and Gen light was off.

 

Next ride, Gen light was working at the start. But, same issue occurred later. After running for a while, Gen light didn't light up after stopping, but started working correctly after a couple of hundred feet.

 

So far I have replaced the voltage regulator and put a dvm on the diode board and rotor. The rotor measures 6.2 ohms which EME says is in range for this rotor. Tested the diodes and they all were okay for only passing current in one direction.

 

Seems like an intermittent rotor problem. Do I just keep riding until something fails hard?

 

Any other suggestions for figuring this out?

Morning Michaelr11

I let this thread run a while to see what feedback you might get from others first.

I didn't want to post this up at the beginning as it is/was a very rare failure.

I worked on a R100 back a few years ago that had an intermittent charging problem-- been worked on by dealer & a couple of independent shops but they couldn't find anything as it seemed to work OK when they looked at it.

In any case it turned out to a partially failed solder joint at one of the rotor slip rings, also found that slip ring slightly loose so needed to use a thin epoxy to re-secure it then turn the slip ring in my lathe to get it to true again (very unusual failure so posted here as a kind of last resort thing to check)

Thanks D.R. Hopefully I will have a better grasp of this issue in a couple of days.

Further examination under the front cover reveals the front brush wire lead is very tight. It appears to me that when it was soldered on, it was placed so the wire is exiting the solder joint to the right and then has to make a loop up and over to the left. This appears to have reduced the amount of available wire lead. The back brush lead has plenty of slack in it. It may be that the front brush is touching the slip ring when the engine is cold and when running (vibration?) but when the engine is hot it hangs off the slip ring so the light in off. We'll see..... I ordered a set of new brushes from Rick at Motorrad Elektrik. I'll install once they arrive, and try to get some before/after photos.

I think this problem is resolved by installation of new brushes (only installed one so far) from Motorrad Elektrik.

I loaded up a link to four photos.

It looked like one of the brushes - the front - was on a much tighter wire lead than the rear brush. The photo of the old brushes shows how the front brush was soldered with the lead positioned in the wrong direction, forcing the lead to travel out and around, losing most of the slack.

The new brush has a ring terminator making it super easy to attach to the brush terminal instead of having to solder the new brush in place.

A 20 mile test ride with the new brush installed has all charging back to normal. The GEN light is functioning normally and the Gen light is going out at about 1500 RPM which is the right function.

One Drive Photos