More input
....
You obviously want to pimp up your ignition system?
Sorry I'll take it a bit OT to get back to the topic later.
The most simplest of the Kirchhoff laws (Volt = Current x Ohm) does not apply much in the 2nd circuit of the ignition system as there are other parameters the Kirchhoff law does not include (time, inductance, frequency, capacity, reactance...).
In most cases it is OK to go with ONE 5 kOhm resistance (plug or cap or cable) it won't "weaken the spark" at all.
It can even make things worse as the insulation of the high voltage (1st part of the spark process, spark gap acts as a capacitor) and high current (2nd part of the same spark process, spark gap becomes a resistor, the resistor is the "spark" = current in ionized gas) gets more critical and one obviously wants to have as much spark power as possible to end in the combustion chamber and not somewhere else.
Now back to the topic (I think). The coils you've mentioned have one in common.
1. Low primary resistance
2. Designed for transistorized ignition.
Regarding 1: While the primary resistance of a coil
is very important (indirectly responsible for the maximum energy the coil can "store", it is not the only parameter that matters. E.g. the inductance of the primary coil has to be tuned to the dwell time of the ignitions system. If you go for a new coil leaving everything else of the ignition system as is, a
new stock ign. coil or an aftermarket coil identical to the stock coil is your best option. New means unused.
Regarding 2: One reason for the low resistances of coils fitted to transitorized ignition systems is the voltage drop in the power transistors used. The voltage drop is quite a bit, so to compansate this, the manufacturer goes for a low resistance to compensate this. With points you don't have much voltage drop, given that the wiring and all connectors are allright, 5 Ohm as a prim. resistance is not a problem.
Another route manufacturer go, is to establish an rpm dependent electronic dwell time control, so they can go with a low primary resistance without blowing the coil after two minutes with low rpms.
In my opinion, the stock coils are more than sufficient for stock engines with stock specs.
On the other hand, from my very personal experience, half of the ignition coils that have served more than 20 years have a problem with the insulation even if they look good at first (primary/secondary resistance tested good), the other half is completely shot...ok that was mildly exaggerated..
Only if you plan to increase compression ratio, rpms, or go for a much leaner mixture (read race) or reliability is not your cup of tea etc. you will need something else.
Imho your best option is to get rid of the points, and go for a complete ignition system out of one hand designed to fit your bike (dyna, silent hektik, boyer etc.). This will give you more ignition power (can't hurt) and will also increase reliability.
Your next best option is to get rid of the 20+ year old coils, and replace with new ones of the same type.
