I know enough that it is undesirable to use a suppressed (resistive) cap with a resistor plug and desireable to use a suppressed cap with a non resistor plug. Reading the manual for a Villiers A15 ( the later incarnation of the original F12 Sloper) is says that the electronic ignition system “ will work most effectively with a resistive plug and non resistive plug cap” . This particular engine is runs quite happily once running but does need an un-Sloper like sharp tug to fire it up; a characteristic that I’ve noticed on a number of engines with electronic flywheel magnetos. This engine has a non resistor plug and, what appears to be a non resistor plug (NGK LZFH),so it will be returned to its owner with the correct combination – always assuming that it starts and runs!
So the the question: any thoughts on ignition theory, or experience of ignition issues that may result of incorrect applications and combinations?
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