RCEXL has developed a CDI test kit. Also a sensor test device. Plugs into sensor connector and with spark plug attached on plug cap, if you connect the battery you can test from 400 rpm to 20.000 (as instructions says) . I've tested the CDI device and the result is A LOT OF SPARKS. It can be used to check suspected bad CDI, batt consumption and more.
Look and
ear this video (sorry for the quality) . The sound is from spark only , and it sound much more than 10.000 rpm
http://www.youtube.com/watch?v=8Cw3p-Sz2GE
Regards