‘79 XS750

[tbanks1382]

I bought a 1979 XS750 last summer. It was built as a bobber at some point but need a little finishing. The wiring was just hanging all over the bike. I cleaned the carbs and got it running enough to ride. Over the winter I took it all apart and added/painted a few things to finish off the look. I decided to rewrite the bike since a lot of wires were missing some insulation. In the process I decided to simplify the bike and eliminate the electric start. I labeled everything while taking it apart and spent hours putting together a new harness making sure each connection was tight and weatherproof.

I hot wired the starter motor to make sure it would start and found out I have no spark. I used a multimeter to make sure all the coils tested good but still no luck. The picture below is essentially the wiring I have. I wanted to make sure the bike would run before I wire up head/tail lights and what not.

What am I missing?

 

[Signal]

From your diagram I cant see where you have power to the ignition unit.

 

[Grewth]

From your diagram I cant see where you have power to the ignition unit.

I think you may have hit the nail on the head there !

 

[tbanks1382]

I kinda thought it needed power. Looking at other threads on here I don’t see where a positive lead from the battery goes on that ignition unit.

 

[Signal]

I have an 850 diagram in front of me:
The Red /white from the start switch powers the coils and the ignitor.
Looking at the back of the ignitor 6 pin plug where the wires come out the Red /white goes in the top row middle connector between the yellow and sky blue wires.

 

[tbanks1382]

Got it. So by eliminating the electric start I subtracted the power to the ignition unit. So as a way of bench testing that could I splice a wire from the red white into the battery to ensure it works before I reassemble the bike?

 

[Signal]

You could if I was doing it I would put a fuse and switch in the circuit. Fuse for short circuit protection (think fires) and switch so you can shut the motor down quickly if you have to.

 

[tbanks1382]

Good idea. Thanks!