Add to Your excellent post Sonreir:

Watts = Amps x Volts

Amps = Watts/Volts

Volts = Watts/Amps

So to determine the Amps a 60 Watt headlight bulb needs:

60/12 = 5 Amps

Your ignition coil is 5 Ohms (Stock)

Using Ohm's Law, 12V/5 = 2.4 Amps

Now, put one of those fancy 3 Ohm Coils in:

12V/3 = 4.0 Amps.

Better yet, remember, the alternator runs the bike at 14.5 volts when running properly.

14.5/3 = 4.8 Amps -

Wonder why your CB350 with a 110 Watt alternator is losing its charge?

110 Watts at 12V = 9.2 Amps

110 Watts at 14.5 Volts = 7.6 amps

So what happens with a 60 Watt / 5 amp Lamp and a 3 amp Ignition? 8 amps leaving 1.2 amps for the other lights and charging the battery.

Now do 60 Watt lamp and 3 ohm Coils: 5 amps and 4 amp = 9 amps...nothing left from the alternator to charge the battery.

Keep in mind, the resistance of bad connections, wire length, all contribute to current use, and these numbers are based on a NEW CB350, not a 40 year old one.

Another note, the ignition does not draw the full amps continuously. It has about a 25% duty cycle, so 75% of the time, it is drawing nothing.

However, your 40 year old alternator probably isn't producing its full wattage either.

Some food for thought.