replaced the cdi box on a bike only to have it pop.what could be my other issue?

What you mean pop ?
Cool.
Buddha.

it literally made a pop noise and blew a split in the casing!!!! would that be a voltage regulator? never seen it happen before.

Probably over voltage. Excessive voltage can make capacitors and transistors explode.
I assume you replaced it because it went out? Can you give a little history of the problem?
Did the lights go really bright? Did any lights bow out?

I'd replace the voltage regulator.

You could disconnect it from the battery and run the bike just on the battery for a few minutes. Measure the voltage coming out of the regulator.

Pretty hard to test a regulator without the bike running.
I'll have to figure out a way to test a regulator under load off of a bike.

CDI - well we dont have cdi, we have TCI. OK that only controls the spark advance - If I recall.

Well the split case isn't doing you any good now, but I have a TCI well ... the dog ate my tci.

So well the cruel experiment in the name of science I propose - we cook your TCI - in MEK or some such horrible chemical. Get it opened up and see what blew up, trace that to the circuit and we will know what the overloaded circuit is.

I dont think you wanna feed it many more TCI's. Then once we open the tci We will know where the overload is, then we can fix that and maybe replace the components that blew and see if it wants to be a tci again.
If its not wanting to be a tci after that, we can chuck it and use the wiring out of it and splice it into my "dog ate my TCI" and we can see if it wants to be a TCI again.

Of course if yours is a 04+ forget everything I said, OK well forget some of it, but we cant splice it into mine.

Cool.
Buddha.

We have a CDI or ignition control unit. Your solid state ignition unit because we don't have points to replace.Its on the left of the battery box. People call that box different things. I think ICU is most common for Ignition Control Unit.

It makes the spark. The timing rotor and various switches go into it. Its a big square box on  the lower left of a wiring diagram.

Older ones mainly did spark as there were 2 ignition pickups that determined the timing. The newer ones calculate the timing for the spark based on a single pickup, throttle position sensor and the gear indicator that indicates you're in 1st or 2nd gear. That box also controls an air/vacuum valve on the newer carbs.

all that info made my head hurt!!!!!!! i just swapped out the regulator and the brain.all is well now! the bike had sat for 6 years;one thing failed after the other. only thing left is to upgrade wheels or buy tires.....torn  over leaving stock or start moddin...