Just wondering..I have a ‘72 dt250 and have looked at a few schematics. Some show a diode symbol in place of the rectifier/reg. Does the rectifier/reg also function as a diode?? I’m working on adding a 6v battery and may need a diode if the reg/Rec doesn’t do it already.. bike was chopped of all electrical years ago. Thanks I’m advance.

I have the same bike, you'll be fine with the rectifier. 

What you're seeing is a diode symbol because that's what the rectifier is...  and that's ALL it is. 

Old magneto electrical systems were very "analog" relying on balancing of the fixed magnet strength output of the magneto against the electrical load to regulate voltage. 

No such thing as a combination "rectifier/regulator" on a Yamaha Enduro for about a decade past 1972.  However, a separate AC regulator was added to the headlight circuit starting with many of the 1976 two stroke models. 

 

Interesting!! Makes me think I may want to add an AC regulator for my headlight.

Depends how closely you're following the original wiring design. 

If you kept the split AC-DC system, yes, a regulator on the AC (headlight) is a good idea. 

Was wondering why does it have a split system? Anyone?

cliff