MG Car Repair: Resistor on MG Midget, electronic ignition systems, blue spark

Question
I bought a 1975 Midget on which the ignition has been changed to electronic instead of points.  Is the ignition resistor between the coil and distributor still needed?
I ask because I read that I should be getting a "blue" spark at the plugs.  My spark is more "yellow."  

Answer
Hi Zane,
Yes a blue spark is an indication of a strong spark (checked inside or in the shade) A hair thin yellow or orange spark is an indication of a weak spark.

The resister is part of the coil circuit and depends on what coil you have and the requirements of the electronic ignition.
A resister is usually used with a 6v coil (1.3 ohm primary) when used with most electronic ignition systems. Also the resister is bypassed while in the "Start" position so as to supply a full 12v to the 6v coil and as the key is released back to the "Run" position, the power is then routed through the resister or resister wire to the coil thus reducing the voltage to the 6v coil.

Your car the (75 Midget US ver.) came with the Opus/Lucas electronic ignition and used a power resister for the electronic ignition and also used a resister wire to power the coil and had the bypass system.

If you have the Euro ver with points, you only had the one resister wire and a 6v coil with the bypass system.

You should try to ID the electronic ignition and contact that manufacture or supplier to find out if a 6v coil was required.
Howard