87 fourtrax 70 no spark

Picked up a fourtrax 70 for the kids yesterday. Needless to say they are more than anxious to get going but no spark. I cleaned up all the grounds and checked and cleaned connections. The grounds and kill switch seems to funtion ok. Key was eliminated wires are just connected together. How can I tell if there is power to the coil? What would be the first place to start on this problem cdi, stator, pulse generator? I pulled the side cover but didn't have a flywheel tool so thats still on there. It was suprising clean inside no rust. So are the aftermarket coils and CDIs for sale on EBAY junk or will they work.