For coil wires, are you referring to the 2 wires from CDI to engine or plug wire. You can use a 7mm auto plug wire if that needs to be longer. If you need to lengthen the CDI wires, you can splice in a wire. I used about 2' of lamp wire on my build and it is fine.
Here's pics. CDI is behind the seat post and the wire runs down the seat post, under the bottom bracket and back up to motor.