My first thought was to pick up Rick Jones Classic Boxer Charging to see if it would lend some insight. In reading through his book, it seemed like my Voltage Regulator may have been the issue. But, I swapped out, what I believe to be a functional, used voltage regulator, and it did the same thing.

In full disclosure, I had one of the moments when putting the bike back together, that makes me feel a little less than bright. Fairly recently, I replaced the battery with a MotoBat. They seem highly regarded and I've been really pleased with it. However, these batteries have 4 connection points rather than 2. And I found out the hard way then the connections aren't symetrical.  Obviously, I wasn't paying close enough attention when reinstalling the battery and had it sitting in the cradle backwards. I attached the positive terminal first and then when attempting to hook up the negative terminal, I was treated to an impressive sparks show. It took me a minute to figure out what I had done. I then swapped the terminals, turned on the ignition switch and everything seemed to work as it should. 

This past weekend is when I finally had the bike ready for its first spin. It started just fine and seems to run with no apparent issues, other than the generator light burning brightly as I motor down the road. I'm wondering if I have fried the diode board or maybe something else. Any sagely advice would be greatly appreciated. 

Much appreciated. 

Bombadil

Thanks, Matt Parkhouse hobomatt@aol.com

Longtime lurker, I just joined the community today.  My 1988 R100GSPD Bumblebee has remained stock for 27 years of ownership, but I never took the beast too far off road.  Pick it up 4x in sand or mud and you will start looking for weight savings...

DURABOOST lithium ion battery shows 13.3V at the terminals.  Rev to 3000 and the voltage spikes all over the place.  28V 30V?  Scrambled numbers hard to read on multimeter.  Collective wisdom here says it's the VR.

Yesterday, my AIRHEAD friend emailed this same question to you experts, and the team answered the call!  "BP", Dave F. and others responded to my pal via AIRMAIL, and steered me in the right direction.

Thank you for the quick responses and suggestions for a solution.  Voltage Regulator replacement in the mail.

-Chris "Big Bird" Ryan

I’m looking to do a full teardown and restoration, and while I want to do the heavy lifting myself, I’m looking for an experienced Airhead mentor in the Los Angeles / South Bay area to guide me through the process.

Being a '74, I know there are some year-specific nuances (the switchgear, the five-speed trans quirks, the Dell'Ortos) that I’d prefer not to learn the hard way. I’m a beginner. Never done this. I just need the 'Airhead wisdom' to ensure this classic stays period-correct and mechanically sound.

If you’ve restored an R90S before and wouldn't mind a 'student' looking to get their hands greasy, I’d love to connect. I’m happy to host at my place or bring the bike to you. Coffee, lunch, and deep appreciation provided.

Reza in Redondo Beach 

I got a new stator to upgrade the wattage of my charging system and I’m wondering if I should replace the rotor as well. It looks a little rough and there is a copper band that you can see in the pic that is broken and moving around. Should I replace it or is this normal?

thanks!!