I just noticed that the turn signals on my DT don't work properly when I am riding my DT/with the engine running. All lights/horn work as they should and the turn signals function properly including the indicator light without the engine running. As soon as the engine is running the turn signals act up they kind of stay on with a bit of flickering but not really blinking. The only thing I can think of is that the bike has been sitting a couple of months and the 6V battery might be weak? Something to do with charging voltage, vibrations of the running engine impacting the relay?  Any ideas - thank you very much!

If they work with the engine off, I doubt the battery could be weak?

First thought is bad rectifier....  generally that would cause the battery to drain though.  So maybe flasher is falling apart internally and vibration is causing the problem? 

That's all I can think of

Flasher relay suffering from vibration can do funny things but if it's rubber mounted then not that.
Not sure if overcharging into the battery would cause that.
Yours would have a regulator by "75 so no overcharging.
Wonder if a battery can be internally faulty & only show when motor vibes get involved or charging is going in.
Your headlight runs off the mag? just asking incase someone's hooked it to the battery.
Is your tail light battery powered as ours in NZ run off the mag along with the headlight & instrument illuminating bulbs.
Maybe bad loom earth or bad flasher earths. I dunno, i'm no use haha.

Thanks for your replies!
Headlight & instrument illuminating bulbs run off the mag, tail/brake light, turn signals and horn run off the battery and all work as they should except for the turn signals with the engine running. I guess as a next step I will have a look at the relay.
Thanks again!

Is one of the indicator wires running very close to the coil or ht lead?

Good point - I will have to check - I had the entire bike stripped down to the naked frame so there is a chance that one of is running very close to the coil or ht lead - I'll check - thanks for the comment!

Quick update on the flasher relay - I replaced it with a new aftermarket 6v - 3 pin - relays. It worked with and without the engine running - for a bout 5 min. After a quick 5 min ride around the block it is now no longer flashing (it just stays in flickering mode) with and without the engine running. Any chance this could be caused by heat (considering where it is located - between gas tank and cylinder head) or are the vibrations simply killing the mechanical relay?

Did you connect all three wires?  If so, your problem has likely been a bad ground to the original flasher.  A new three prong, unless you bought Yamaha NOS (stupid expensive), would have a direct short if you hook up all 3 wires.

You only need a 2 prong flasher or you can use 2 of the 3 wires on the modern 3 prong...  the "P" terminal needs to be insulated and not connected to anything.

Puttin’ my neck in a noose….
The older flashers sent the power to the blinker tube, then to the switch, which then, sent it to the designed winker…

I think you've got a bad ground or possibly power side connection, but I'd search out the ground side of the circuits first.

I was thinking voltage regulation but with the same symptom now with the engine off points to a faulty connection, especially the faint flickering.