On your fuses, the one with a red wire on each side is the main fuse, 20 amp.
The one with red/white wires is the ignition fuse, 10 amp.
The one with red/yellow is for lights, 10 amp.
The one with brown wires is everything else. Use your meter check the battery voltage, When you check voltages at other places it should come very close to this voltage.
With the key on check the voltages at the fuses. The red/white wire is the one you need to check. If it has battery voltage fine, If not check the fuses, main and ignition and the key switch. The switch can have dirty contacts inside. Most can be taken apart and cleaned.
Once you have battery voltage at the fuse check the voltage at the red/white wire at the coil and the TCI box. They both should get a reading within .5 volts of battery voltage.
If not check the kill switch, dirty connections inside will prevent power passing through. If you have good voltage at the TCI box and coil check the grounds at the TCI box and coil. You need good grounds.
If everything checks out good and still no spark you need to check the coil for proper ohms. On the 81 the primary side, the red/white and the orange wires, With your meter set on it's lowest range, touch the probes together, this reading is just the probes and wires, you need to subtract this reading from your test reading to get the actual reading.
Now touch a probe to the red/white and one to the orange wire, If it reads 2.5 ohms + or - 10 % then that parts tests ok.
Now with your meter set to the 200k position touch one probe to each spark plug cap. This way you are testing both caps, wires and the coil. It should read 23k ohms, + or -10%.
Now down on the stator is the pick up for the TCI box. There is a connector for them by the connector for the stator. At this connector there will be three wires, one black/white, one white/red, one white/grey. They used different colors sometimes. Too check the ohms check from the wire that has black on it to each of the other wires. The reading should be about the same and some where in the 700 ohms range.
These are about all the checks you can do on the TCI system. If all these checks are in spec the TCI box is the problem.
There are several things you can try to fix the TCI box. Re soldering any cold solder joints. Re soldering all the joints. Replacing any parts the look burnt up. Usually the transistor and some diodes. If you look around you will find the threads that explain just how too do these fixes.
If fixing the TCI box fails, then you can spend money trying to get a good replacement from forum members or off ebay. These can get your bike running. Unless you get a NOS replacement in the $500 range you will get a 30 year old used part.
There are several aftermarket ignition systems out there. I'm using the Pamco system and like it very much.
The Boyer Branson is popular too.
So pays your money and take your choice.
