Yep. I removed the rear flywheel it Prizes off ie straight out and has a small semicirle key in shaft.
Then I rempurchased this http://www.hobbyking.com/hobbyking/s...idProduct=6292 Plus a sensor pickup elsewhere same site a Lipo Battery and Voltage reg to keep it at the required 6V max and a tiny rare earth magnet
I drilled an 1/8th hole in the prop waher/base aluminium boss on the shaft and epoxied the magnet in flush.
The sensor can be flipped over in its plastic holder to get the right Mahgnetic pole.

The sensor is mounted so it is just over the magnet. When the shaft and magnet rotate the sensor is activated and initiates the spark.

You need to figure 26 Degrees BTC (I yhink) to find wher to mount the sensor an magnet. see http://www.rcextremepower.net/ignitions.html

The sensor can be adj a s bit each way with the 2 mounting screws

To Set up the spark angle see http://www.youtube.com/watch?v=GBXFpxWg7vY

All done