[Here is the rub]

Strange how you can work on motor vehicles for decades and here I am in my seventies and have just come across a question from an individual who had asked me to fit what now seems to be commonly called a "Sports" ignition coil. This experience came about as we were fitting his "Sports" coil alongside electronic ignition.
His question was along the lines of "Is it really necessary to increase the spark club gap". He was thinking the higher performance coil would give a "fatter/hotter" spark with the normal gap.
Now then of all the devices that is truly difficult to put into words with regard to "how it works" there are few things more convoluted. Probably easier to say how a nuclear reaction can occur. 
So here are some words that miss out a mass of physics. A coil is akin to a transformer. It`s workings cannot be explained fully without taking into account the interaction between voltage and current and vice versa. But a bit of stuff......  The coil has a primary winding and lets see it has 10 windings. Lets say also the secondary has 100 windings. Theoretically 10volts at the primary gives 10 x 100 volts at the secondary. i.e. 1000 volts but in reality there are losses so lets say 920 volts. A "Sports" coil has a different ratio of windings. More secondary so the resulting voltage in my example would be say 1200volts.
There is an additional function that the condenser carries out. As well as preventing a path for a spark across the points gap it is needed for the coil to function with quick "climb" & rapid "drop off".   
All well and good so far.......  Here is the rub. With a standard plug gap the full output of the standard coil will be in the region of say 20,000 volts. Enough for the spark to jump the plug gap. Fit your "Sports Coil" and leave the plug gap standard and the coil voltage will rise up to the point to bridge the gap and no more. To get the increased output from the coil the plug gap must be increased. There is an old school "rule of thumb" that states 35 thou gap but every engine & ignition system is different so it`s a case of increasing the gap a bit at a time until you reach the max gap the engine will start, idle, fast idle and accelerate smoothly.

Well I dove in at the deep end with ignition coil stuff so might as well add a bit about battery/alternator relationships. You can never have too much info in your head... or can you      

A good battery, with a full charge, produces 12.6 volts. An alternator is regulated to produce a steady 14.6 volts under all conditions, within it`s capacity. If the load on the alternator increases the internal regulator increases the field current to maintain the 14.6 volt output. With 12.6 volts from the battery and 14.6 volts from the alternator, all of the vehicles electrical loads are being supplied by the alternator. The battery cannot supply current as long as it is being fed from a higher voltage source. As an example say you set off for a trip up or down the M1 of hundreds of miles the only time the battery ever supplies current is when you stop at the service station for a wee or whatever and then go to start the engine again.

So I am hoping this, and the previous post, gives some insight into what your buggy`s electrical system is doing whilst you sit there soaking up the attention as you pass by people on the streets. Your expensive petrol isn`t just getting you from A to B it`s a source of all sorts of magic   

Whilst I sit typing away with my aching fingers I hope you can see the relationship between voltage and current. It`s important. When your battery fails and you measure 12 plus volts you may conclude the battery is ok. With just that check you cannot be sure that it is not failing.
How do you check your electrics if you think you have an issue with a light, a fuel gauge, or any other electrically powered item you may have on your buggy ? I often use "continuity" with my meter. Don`t rely on this as it can be very misleading. You may find you meter indicating "continuity" of the wire you check but, for example, the bulb does not light up. Ah you say.... the bulb must be duff. No says I your bulb may check out all ok so what you say is happening here ? It`s the use of the "continuity" check with your meter that has lead you up the garden path. The wire can allow sufficient current  thro` to cause the meter to react and indicate continuity exists but not enough to give a voltage reading. This scenario simply means the wire has gone bad at some point or most likely you have a duff connection somewhere in the circuit. All good stuff for a cold, wet January day when you are in the house bored stiff....