Hi guys,

My DT2 that I'm working on loses spark (or gives very weak spark) when i have a fully charged 6v battery hooked up.  If I unhook the terminals, it gives very strong spark with the plug that was in the bike (NGK BR8ES and has run with).  If I hook it back up and use a different smaller plug to test (NGK D8EA), it throws a weak looking spark.  I can get the tail light to work and horn with the battery attached so I know the fuse is ok.  Any ideas that I could look for?  Electrical systems arent my strongest area, so hopefully this is something simple.

EDIT:  I may have found the issue after looking at the wiring diagram in the manual, but I'm not sure.  the ground wire from the battery...should that go into the wiring harness black wire with the 3 female connectors?  The previous owner had it going to a black wire that was coming from the cluster of wires out of the stator harness.  it was spliced into a second black wire?  The bike ran fine without that plugged in and that has to be the issue.

Thank you!

Yes, you found the issue! 

To answer your questions:-

Black from battery goes to frame - I've used a ring connector on the bolt next to the battery holder.

Triple black female is for the earths from the two indicators and the earth from the rear light.

The single black female, halfway up the wires from the generator, is for testing purposes and shouldn't be connected to earth. 

You did well, very well. There's Blacks & there's Blacks--just to confuse us. Sounds like battery was earthing into the mag black which is ignition from the mag, points condenser & source coil. I'd say that's a 'First' for that to happen but chalk it up as another one we'll never forget & probably never see again. Thanks for the post, most interesting & brain teasing or would've been if you hadn't solved it.

thanks guys, I'm proud of myself lol  i appreciate you chiming in to confirm for me.  the original manual can be so vague!  maybe i missed it, but i dont recall seeing anything about that extra single black wire coming from the generator harness used for testing.  i would have never known!  i also saw there is a white wire with a female end on the harness thats also apparently for testing.  its like the engineers added that stuff and never mentioned it in the manual to mess with us 50 years down the road lol

thanks again!

Matt

I think that the "spare" white wire is to boost battery charge if the standard one is struggling. I've never read about anyone ever having to use it, mind!