You can give your custom wiring harness a factory look
with Japanese style bullet connectors, and a ratcheting crimp.
They're easy to install and easy to maintain.
Non insulated ratcheting crimps are the best and most secure way to
attach you bullet terminals to wires. Cheap ones can be found online (About $25)
And a good pair will have the removable jaws for your other crimping needs.
Other non ratcheting crimps can be used, but you will never get that accurate
professional crimp like you will with the ratchet crimp.
You only need to strip the wire back a little
Setting the wire on the terminal, you can see the first tabs are used to clamp
down on the wire insulator. The second set of tabs are used clamp down on the wiring itself.
Before you crimp. Make sure to slide the clear insulator or shrink tube over the wire.
Place the terminal in the slot as shown. Notice the two jaws. Each will crimp the tabs (shown above)
perfectly at the same time. The numbers shown on the jaws also indicates the corresponding wire gauge used.
Ratchet down once or twice to hold the terminal in place.
Push the wire thru. The insulator should stop the wire from going further
at the back of the wire tabs.
At this point, looking at the other side. The wire itself should only slightly pass the wire tabs on the terminal. You can now start ratcheting down. The crimper will spring open when the crimp is complete.
Your wire and terminal should now look something like this!
If the crimp is good, the terminal should not come off without a great amount of force.
Slide your insulator or shrink tube over the terminal and you're done!