Need help with electricals

[jakefromstatefarm]

Hey guys. I'm rebuilding my first bike (1979 xs400F according to title). It hasn't ran in a little over 30 years, so things are a little guess-and-check, but it's been a fun learning experience.

I'm finally getting to the ignition timing tonight. I have the gaps at .015 inches and am using an automotive voltage tester to check for when the light comes on and off.

Here's my situation (please excuse any ignorance - I'm eager to learn all I can).

If I hook the tester up to the battery's positive mount and to the left cylinder's timing coil, I get a solid light that won't even flicker as I turn the engine over. However, if I mount the tester to the engine block and the timing coil, I get zero light.

As for the right cylinder, hooking up to just the ignition coil and the engine block still results in zero light. However, the light will go from normal brightness to extra bright at what I am almost convinced are completely random intervals as I rotate the engine, if I have the tester mounted on the positive battery terminal and the right cylinder's coil.

Something else that might be worth noting... The tester will light up even with the key out of the ignition. I assumed that when the key was off or out, the circuit was broken and you wouldn't be able to get the tester to light up anywhere. Does this mean something else is drastically wrong? Will my battery likely drain?

I've been in over my head since the beginning but have managed thus far, knowing all along that the electrical components would be my greatest struggle. Any advice in troubleshooting this situation would be more than appreciated.

Thanks guys, you're the best.
Jake

 

[BBS360]

There are no coils involved in checking the timing.
Your light should be from + to the lead from the contact breaker that you're checking. Disconnect the contact breakers from the ignition coils if you haven't already.

If you are connecting from battery + to anything grounded then the key switch is not part of the situation at all. Completely normal that the light would stay on with ignition off.

 

[jakefromstatefarm]

Sorry - I shouldn't have been using the word coil. I meant the small sheet-spring labelled "B" in this photograph. I'm assuming we're on the same page?

Good to know about the battery-to-ground light.

 

[jakefromstatefarm]

Update - I roughly timed both sides just using my eye (no light tester), unplugged the points lead wires from the coil assembly (didn't previously know that made a difference), and retested both sides with the light.

LEFT SIDE
Again, the light remains on throughout the engine rotation, even when the gap breaks contact. Perhaps something is touching that shouldn't be?

RIGHT SIDE
The light shuts off right as the viewport needle crosses RF. This is correct, right?

So I just need to figure out why the left side won't shut off when the points break contact. Any ideas?

 

[BBS360]

If you can see air between the contacts when the left opens and the light is still on then something is conducting that shouldn't be.
The other end of the orange lead wasn't touching anything?
If you have a meter you can do a resistance test between the orange wire and the motor when the left points are open. Should be near infinite resistance.