Ignition module failure modes

I must admit that I haven't come across those symptoms being tied to an individual module but there is no argument with your conclusive test results.

There are 3 distinct sections to the ignition module circuit:

1. The input trigger circuit.

2. The coil drive circuit.

3. The power supply which includes the charge store and the kill circuit.

My gut feeling is that it is possibly in the input trigger circuit. There is some filtering effect that results in it missing some pulses at particular RPM and so the coil drive circuit doesn't fire. The trigger circuit has 2 paths, one that detects the pulse from the leading edge of the flywheel notches, the other path detects of the trailing edge. The angular length of the notch determines the different timing between cranking and running. This in itself is determined by the amplitude of the pulses from the pick up coils which is lower at cranking speeds but increases at normal running speeds. We know that this amplitude threshold can be a problem in some modules which is why they won't start and engine but will happlily sustain it when it is running.

There may be a problem in this area of the circuit that gives the symptoms that you describe. If you are in the UK, there are some Rotax modules for sale on afors.com or alternative just replace them with Ignitec and have done with it.

Watch the 2nd half in particular.

https://www.rotax-owner.com/en/videos-topmenu/free-videos/695-Rotax-lockwood-ignition-troubleshooting

Yes I've previously seen and taken note of that helpful video thanks.