RE: YS cdi voltage
No. The plug gets very high voltage sent through the high tension lead from the capacitor.
With the engine running, wriggle the lead that goes into the back plate. If the engine misses then the sensor lead wire is broken. The vibration causes it to break at the point where the wire is hard soldered to the back plate. I have had this problem with my 170 and 175cdi's. I made a small bracket to support this wire and so far i haven't had this problem again.