Aim for a gap of 0.5 to 0.7mm
Any larger may get you in trouble.

@ Gadi
RCexcl ignitions do not use a coil, but switch conductance when near the right magnetic polarity.

The hall sensor is not bi-polar, so it is sensitive to the magnet polarity. The RCexcl manual included with the ignition shows how to test and fit the sensor so the ignition will work. Only when working OK, should the sensor be secured in the housing with the small taper thingy that is included.