It seems that my '87 isn't charging. I have the service manual and will do some testing but was wondering what would be the most likely culprit: Bad stator? Bad regulator/rectifier? Other?

 

rectifier is the most likely culprit. take a look at it and see what it does.

 

That's what I'll try first...thanks. I'll let you know.

 

id check the battery too

 

ya, but the r/r is known for fudging up

check em both

 

Picking up a parts bike tomorrow...should have both. I'm gonna test and swap as necessary.

 

Make sure you have a fully charged battery when you start testing. I will repeat myself again and again. The charging system is designed to keep a fully charged battery charged...not to refill an empty one. If you start with a dead battery you WILL damage your shiny new parts and have to start over.
I offer this advice with the experience of having ran a starter and alternator shop for three years with my father. The charging system failing is a SYMPTOM of a battery problem. Replace the battery or at least have it load tested to verify its condition.

 

This is what happened to me. The battery was dead when I bought the bike. Jumped the bike off rode it home stuck it on a charger. Battery never charged, put a new battery in and it seems to be charging just fine now. Haven't rode it much since the rear wheel is way out of alignment and the chain is full of slack which I'll be taking care of soon..