Looking for a CDI box for 2000 Big Bear 400

[Mech]

Quadman, the cdi probably blew because when you disconnect the battery while it's running, and charging, the voltage goes up before the regulator has a chance to prevent it. There is a "spike" in the voltage that is too high and shorts through insulation or components.

The voltage regulator is designed to be connected to a battery and always expects some small amount of current to be going into the battery. It struggles to chew up all the excess power when there's no battery connected. It's regulator adjusts too slow. Once the battery is off, and the regulator has adjusted, they often seem ok, but the voltage spike can take out any electronics, such as cdi, dashes, efi systems.

[QuadMan49]

 Thanks for all the feedback!

Here's how the original CDI got blown: After riding several minutes the ATV suddenly stopped and quit running. I quickly found that the positive terminal on the battery broke off while riding from all the vibration of 20 years. (The engine was not running at this point)

After wedging it back on, the quad started up & ran fine, but due to the bumpy road the cable kept coming off, the engine dying each time. After doing this three times the 4 wheeler would only turn over, and as it turned out, it lost spark because the CDI got blown.

Edited June 8, 2023 by QuadMan49

[Gwbarm]

That does make more sense as to what happened, CDI just couldn't take that much fluctuation of power, I think Mech explained it very well.