Besides the fuse, ignition switch, and the start button - the other thing that need to work is the brake switch. This is a safety interlock that keeps the quad from starting up unless the brake is applied. And that means the brake light must be on.

When you apply the brakes (ignition switch on) does the brake light light up? If not, then play around with the brake switch and see if if you can make it light up. Measure the DC voltage on both sides of the brake switch to ground. It should be 12 volts on both side when the brake is applied.

 

UPDATE......... Ok I replaced the battery. Put on a used CDI box for testing and I now can jump it across the starter relay and it will start. I still cant start it with the starter buton. I've checked the handlebar switch, the brake safety switch, and the tether and they all seem to be fine.

I wonder if adding a remote kill would help? I bought one yesterday thinking I could use it in place of the faulty CDI....

 

So at least you know the original CDI is not working. Having a spare can make things a lot easier.

A remote control module is not a CDI. It wll not fix a bad CDI. It enables and disables the existing CDI spark via the kill switch pin on the CDI. It also ties into the starter interlock circuitry to allow remote starting independent of the ignition switch and start button positions.

On your starter solenoid there are two smaller wires feeding it. If you have 12 volts across these two wires the solenoid will click closed and the starter motor will turn.

Turn on the ignition and apply the brakes.

1) Does the horn work?
2) Is the brake light lit up?
3) Is there 12 volts on either of the two small wires at the starter solenoid?
4) When you push the starter button does one of the two small wires on the solenoid go from 12 volts to zero volts?

The two small solenoid wires ("A" and "B") are driven as follows:

"A" side (positive side):

1) Battery wire goes to fuse input (red wire)
2) Fuse output goes to ignition switch input (red/black wire)
3) Ignition switch switched 12 volts goes to brake switch input [and lots of other unrelated stuff] (brown wire)
4) The output side of the brake switch goes to the starter solenoid "A" input [and the brake light] (green/yellow wire)

"B" side (negative side):

1) From the solenoid the wire goes to the starter button on the handlebar(Blue/White wire)
2) The other side of the starter button goes to ground (Black wire)