Battery drains completely after about 30 miles or so and I toasted my headlamp. Read the article on the service bulletin about installing a regulator, but too late, lol. Has anyone got a replacement headlamp which has a replaceable bulb? If so, can you post a link?  I searched, but didn't find anything. Was looking for 5.5 inch headlamps, but didn't get a good hit yet. Even noticed a few 6v LED units, but unsure of compatibility. Need to find out why battery isn't charging, but would also like a better solution for the headlamp. Thanks in advance!

It takes a 5 3/4" headlight. Readily available with H4 bulb. Dozens of threads on the topic, clips available from MikesXS or Yamaha.

If the battery drains it should still absorb the charge & save the headlight.
I'm thinking you mean it's draining the charge 'not depleting it of water/acid'.
What does the battery power while your lights that could drain it, or is the tail light battery powered [ours are off the mag in nz]
I might be way off track but just trying to work out what's causing it.
If it's depleting the battery of water then must be overcharging 'big time' but i doubt it's 'that'.
Regulater [bulb saving single yellow wire type] is a good idea but wondering why bulb blowing is happening in the first place.
We were lucky down here in NZ & Australia i think, with replaceable bulb headlights.
People talk about LED lights of which i know nothing, but do they stand up to overpowering compared to bulbs or sealed 6 volt light units.

If you want the "correct" genuine Yamaha/Koito headlight with the bulb replacement facility, then it is part number 214-84120-61 and below is a link to what it looks like.

It was the headlight originally fitted to the DT1.

If you're keen to have one, then I suggest doing a wide search on fleabay etc for any Yamaha or Koito headlight, including using the Koito reference printed on it, as many listings are not accurate - not deliberately, just that sellers often don't know what they are selling (me included, sometimes!).

Depending on what fitments come with any headlight you might find, then you might need to buy a replacement pigtail and bulb holder.

2148412061: Lens Assembly Yamaha - buy the 214-84120-61-00 at CMSNL

Uncle, would that be correct for "73 [just asking] as the link part has that hinge setup that the very first DT1 had [mine had].
Its just that the post heading say "73 RT3 & thought they'd changed by then.
Ok, just looked on partzilla for "73 RT3 which shows the hinge type so i'm wrong again lol & may as well leave this now i've typed it, if only to show my ignorance.
As "Mr Know-it-all" would say [RT325 you really should have known].
ps, need the rubber encased bulb holder too.

Oceania (and European) bikes probably had replacement bulb option for all models, so maybe worth looking on sale sites in those parts of the world?

Looks like socket & bulb #5 & #4 to fit that light unit.

images.cmsnl.com/img/partslists/yamaha-d...gyau1077d-6_a1e2.gif

Part numbers.
www.cmsnl.com/yamaha-dt1-1968-usa_model8313/partslist/D-06.html

Thanks for all the responses! Battery power is being drained, gel battery, so no problem with water. 2 amp charger brings it back in a few hours.  Noticed battery bolt tray which the battery negative wire grounds to only goes in a couple threads, looks like it should be more so maybe a poor ground here, not sure if this is normal. The service bulletin mentions bad ground as possible cause of issue, so will be checking other areas. The joys of chasing electrical demons, lol. Received bike November 11 and while this is aggravating, it's a decent runner. Bike bogged under full throttle, but otherwise ran fine. Removed and inspected external main jet, neat feature! Reinstalled and full throttle bog disappeared! Must have cleared some debris upon removal, accidental victory but I'll take it 

The rectifier is also a common problem for not charging...  if it blows the stator will be disconnected from the battery so the battery won't be able to absorb any power. 

Multimeter arrived and rectifier is OL in both directions. Searched forum for recommended non-oem replacements, but no hits. Does anyone have any recommendations? Found the below, all look like they'd do the job, but would like a recommendation from someone here. Thanks MarkT for the tip! (Put * in front to prevent post from erroring out)

*https://www.ebay.com/itm/285446466491 superplaza02
*https://www.ebay.com/itm/126168454361 Brain Tarp
*https://www.walmart.com/ip/Regulator-Rectifier-353-81970-50-50-6V-For-Motorcycle/5099374256?wmlspartner=wlpa&selectedSellerId=101043407