No spark

I have a 1986 xj700
The left coil functions fine
The right coil doesn’t do anything
I used a volts meter to test the wires from cdi box to coil and I get 12v over both wires on the left coil but I only get voltage on 1 wire on the right coil that isn’t working.
I swapped coils and both are good so it’s definitely not the coil itself. What could be the problem?

 

I would check the wiring connections on the wire you are getting no voltage from. Start from the pickup wire same colour on the end of the crankshaft to the TCI input, check the crimp connectors at the coil for dirt, corrosion, same wire at the TCI. A few days ago there was the same problem on a bike but both coils were dead, it was the black ground common to both that was broken from the pickups on the crankshaft to the TCI. It is only one circuit affected on your bike so it is not the common ground wire. You swapped coils so it is not the TCI unit either.

 

Normal operation for the TCI is on power either the orange or gray will be pulled low (depends on position of reluctor), but after approximately two to three seconds that wire will go back to 12V. This protects the coil if the key is turned on and the bike not started. Once the start button is depressed and the TCI detects a signal from the pickup coil, it will switch from a standby mode to active mode and the Orange and Gray wire will be pulled low with each input pulse from the respective pickup coil

So check the wiring from the TCI to the ignition coil. If the wiring is OK, and the voltage stays low at the TCI on either the Orange or Gray wire then the TCI is likely bad with a shorted transistor. You can check that line with an ohm meter and verify it is not shorted to chassis, or has a very low resistance - a comparison to the good side just to be sure.

If shorted remove the wire to check the harness just to be sure no pinched of chafed wire is the issue, and then check the TCI using the harness to identify pins and check from the shorted wire terminal to where the harness black wire terminal mates to the TCI