Installed all new wiring harnesses, stater flywheel rebuilt by Deet. The bike starts up without the key and doesn’t do anything. The key is not functioning in any position and no power to lights. Seems to be running straight off the stater I’m guessing? What could be wrong?

First thought is forgot to plug key switch in to harness?

Bad key switch?  But odd that NOTHING works?  (Engine needs to be running for headlight to light)

(Key switch grounds ignition to kill spark)

Beyond that there could be several things for each circuit that could be wrong.  Pretty simple to troubleshoot with even minimal electrical skills. 

Yes, to everything you said. Key switch plug and wiring, harness plug wires, all match up. Going to put the old key switch back on see what it does. I’ve done several of these bikes and this is the first time I’ve ever had this issue.

This is the new switch you've fitted?

MAIN SWITCH ASSY. for Yamaha - order at CMSNL

Have you tested the continuity between the relevant wires, as per the "legend" that Yamaha supply, usually on the same page as the wiring diagram? Assuming that I have shown a link to the switch that you have, you can use the same "legend" shown in the 1972/3 DT/RT 2/3 manual.

Daft question (sorry!), but the fuse is in place and wired up correctly?

Figured it out,
The old and the new or reconditioned key switch has one interior part that can be rotated 180°. Both were wrong so none of the contacts were lining up correct. Turned it around and both key switches are working fine now. Whew!!!

The reason my first guess was "unplugged"...  besides having accidentally done things like that myself...  LOL...  was that the ignition switch is basically about 4 switches in one...  and those 4 are independent of each other.  

One circuit is the ignition...  two black wires connect with switch off.

Another is the "battery powered" accessories...  in 71 that would be brake light, taillight, horn, and turn signals...  another simple circuit that connects the red from the battery to the brown that powers the accessories with key on...  (Add blue taillight wire to red and brown when key in "lights on" position.)

The next circuit is the yellow from the stator connects to the blue to the handlebar "hi-low" beam switch and the instrument lighting when key is in "lights on".  Yellow only has power with engine running.

The 4th circuit switches the two greens from stator to the white depending on switch position.  This is the battery charge circuit.

The first three are easily seen/tested without any tools and are independent of each other so it really seems unlikely all three "sections" of the switch would quit.  (The 4th or battery charge circuit isn't as user friendly and while still easy to diagnose, generally a meter or at least test light is needed to check it)

P.S. Looks like you figured it out while I was typing!  Good job!  

"Figured it out,
The old and the new or reconditioned key switch has one interior part that can be rotated 180°. Both were wrong so none of the contacts were lining up correct. Turned it around and both key switches are working fine now. Whew!!!"



And thanks for posting the solution.