I'm working on a 1976 dt250. I bought a new Yamaha right side handlebar kill switch #1R6-83976-01. It has 2 wires the original one on the bike has 1 wire. Will the new 2 wire one work if I just use the black wire with white stripe and leave the other one unhooked?  Thanks Ron 

Perhaps the newer styles didn't rely on a ground through the handle bars and attache it somewhere else?
Sneezles61

Plus 1 on what Sneezles said. Connect the black with white stripe to the matching color wire in the headlight bucket. Connect the other wire to a black ground wire in the headlight bucket as well. There won't be an empty spot in the harness to plug the second wire in so you'll have to locate the group of black grounds and splice in. As Sneezles said the original switch picked up the ground directly from the handlebars. So take a look at the switch base and maybe when mounted it will ground like the original. The second wire may not be needed. Test it without it connected if you don't want to cut into your original harness...I know I wouldn't cut into mine...but each his own.

I'd ground the black wire

Thanks for the help will ground the other wire Ron