chinese magneto/coil question (pep boys dirtbike)

A friend of mine received a 90cc "panterra" dirtbike. This is one that pep
boys and others are importing and selling. The bike "smoked up" them died. I
looked at it and found it had no spark. I ended up pulling the flywheel off
and the coil for the magneto system (no battery) (or lighting) is toasted.
Two questions:
Where do you find one of these replacement coils?
What would make this get hot and fry?
Thanks in advance.

walt
ps. the bike was aquired for free so it's not a major deal if doesn't get
repaired. I spotted a 100cc Yamaha enduro I told him to buy instead.

 

This is a CDI ignition (capacitor discharge) system and there is NO battery
(I believe it MAY have had one before, but now I only see the strap down but
nothing else.) The kill switch on the handle bars (grounding out) was not
on. I think that may have had something to do with the coil (i think it's a
coil... SCR??) getting smoked.
Here's the actual bike:
http://www.pepboys.com/transportation/product_specs/90cc_dirtbike_gasspec.pdf

anyway, that's more info.

walt