RPM Signal from R1 Coil????

[jedi]

Hi there,
Ive got an R1 engine in my single seater (slightly modified loom, but standard coils and CDI) and I need to take an RPM signal from the coils as the standard CDi unit sends out diagnostic peaks due to lack of fuel sensor etc.

Has anyone got an idea of how to take a feed from a coil? (Im a complete numpty when it comes to electrics, so any explanations need to be quite simple really).

Best Regards
Jonathan