I have tried a known working ignition coil, no spark. I actually have a 1985 Honda 250sx atc that has the identical wiring harness, I have used to compare to go-cart.
From the left engine cover I have a green connector with 3 yellow wires from alternator
I have a clear connector with 3 wires total, a blue/yellow, a green/white, and a green
Lastly is the black/red wire with a bullet connector.

 

OK, so if you have a working 250 you can check if voltages and resistances at CDI plug match up. You can also substitute components, one at a time, from the non working bike onto the working one, when it stops working, you have found the faulty part. I go that way, as a bad earth can kill a good CDI for example, so putting the good one onto the non running bike will result in two bad CDIs. That is why I always also check the wires to CDI before fitting a new one. On 300s a bad regulator can also damage the CDI but I think the 250's ignition electronics are completely separate from the battery electrics.

 

Okay so ignition coil and CDI Box were tested separately on the working Honda atc.
And it starts both times. I think I need to test voltages coming to CDI Box... by the way I really appreciate all your help! I should be able to work on it more tomorrow and I’ll let you know what I find!

 

Hey Merryman, thank you so much for all your help, I have spent so much time And wasted money on the go cart, I can’t help but get frustrated because it was running just fine previously. It’s now very cold in Virginia, I have to work on it outside, so I’m throwing in the towel and taking it to my local atv shop, I’ll let you know what happens, he may not even want to work on it he is backed up. Thanks again, like I said I will keep u updated,

 

My local atv shop turned me down because it’s not an atv, back to the drawing board I go.
The last time I checked resistance on my new installed trigger coil, I didn’t get anything, I did test it before I installed it and it gave me about 350 ohms. Where my original didn’t give me any reading, so there might be something making my trigger coil go bad...?

 

Want to see the 1985 Honda 250 sx

 

Can't see anything that could spoil the trigger except the flywheel hitting it. The wire from it goes direct to CDI. Have you checked that wire, could it, not the trigger coil, be shorting out?

Tidy ATC, a farmer, local to me, has just restored one but it doesn't look as good as that.

 

That looks like an old Honda oddessy minus the body.

 

I have checked continuity on it to make sure it was getting to the CDI Box. How do I check to see if it’s shorting out?

 

If the trigger coil has a spade connector like modern ones. disconnect the spade and check if the wire is still showing a short to earth at the cdi.