Electrical issue, i think?

[Elroy]

1974 suzuki gt550.  New battery. After riding with new battery for about 30 minutes, head/tail light go out, starts to misfire then quits.  Unable to get started gain.  Battery drained.  Haven’t messed with wiring.  Wiring issue? Stator? Thoughts?

[Gixer1460]

GS of that age likely to have the weird charging system where 2 phases from alt. go to R/R and third goes to light switch & lights. I'd start at the switch then check the stator. Best solution fit 3 phase R/R with output to battery and rewire feed to lights from fusebox.

[Elroy]

Thanks.  Does it matter if the lights have been wired to be on all the time?

[Gixer1460]

Certainly won't help if there is charging issues! Reading the 1st post again - didn't notice the misfire / flat battery bit . . . . . . you've got a dead R/R = not charging at all!

We this side of the water can choose to run lights on or off so the effect of no switch is unknown to us!

[Upshotknothole]

Our older bikes have switches to turn off the headlights here, I think we lost them in the early 80s. Do wish we still had them. 

Charge up the battery so you can fire up the bike, and measure the voltage at the battery when you start it. If your reg/rec is dead, which is most likely, you won't see any voltage increase with revs. Once you get the R/R sorted, rewire that headlight so you can turn it off during the day.