I'm in Brazil and I have recently received a 1976 RE5-A that I bought on the american eBay.
The bike looks nice, it's very original, but wasn't running. After understanding how its ignition system works, I was able to isolate the problem, it was the CDI. I removed it and sent it to a local technician, who tested all components, identified a few burned capacitors, and replaced them. Now the engine runs just fine, which is a relief.
Today I spent the whole afternoon doing most of the maintenance work recommended by the service manual, but I couldn't identify where the hose that comes off the contact breakers case goes to. One end of the hose goes into the case, the other is loose.
I've been told it's for the vacuum switch that was deleted on single-contact models, but, according to the manual that switch was connected to the intake, and I guess it wouldn't make any sense to connect the contact breakers to the vacuum switch, as none of them are vacuum sources.