Check the voltage at the battery posts (NOT THE CABLE TERMINALS). A fully charged 6V battery will show around 6.3V with the engine stopped. With a properly operating regulator, the battery post voltage should be about 7.3-7.5 with the engine running at fast idle. Adjust the voltage regulator accordingly- - - - -BUT ONLY ADJUST IT WHEN THE BATTERY IS FULLY CHARGED!

IGNORE THE AMMETER- - - - -it's about as accurate as "measure with a micrometer- - - -mark with chalk- - - - -cut with an axe!" It's basically a charge/no charge indicator for dummies. It's normal for it to return to center once the battery gets refilled from running the starter. Once the starting load is replenished, the ammeter will return to near center, and the generator will supply the running current for ignition, lights, and other electrical demand. A big deflection toward the "charge" direction after starting and a gradual tapering back toward center is NORMAL operation.

Insisting on seeing a constant "charge" indication on the ammeter will boil the battery dry and destroy it in a short time. There's a good reason manufacturers stopped putting ammeters on vehicles- - - - -"Idiot Light" is a very good descriptive term for a "no charge" indicator. That light is smarter than all drivers- - - - -and most mechanics!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!