Ignition coils
- Thread starter dumbkid
- Start date
johnd900
New Member
I have a 73 CB450 and I'm currently figuring out ignition coils stuff. This thread is from May so I'm sure you've got it figured out by now.
Black/White wire to the ignition/battery/kill switch - essentially always hot when running.
Yellow or Blue wire depending on the left or right coil goes to the points.
The only other wire is the plug wire, there is no specific ground wire.
I measured my primary coils and got about 4.5 ohms from each. When trying to measure the secondary coil I wasn't sure where to measure. I figured it would be between the plug lead and the mount, but that is open on both coils. Then I tried between the plug lead and the primary wires, in both case I got about 10K ohms.
So where is the right place to measure the secondary coil resistance?
Black/White wire to the ignition/battery/kill switch - essentially always hot when running.
Yellow or Blue wire depending on the left or right coil goes to the points.
The only other wire is the plug wire, there is no specific ground wire.
I measured my primary coils and got about 4.5 ohms from each. When trying to measure the secondary coil I wasn't sure where to measure. I figured it would be between the plug lead and the mount, but that is open on both coils. Then I tried between the plug lead and the primary wires, in both case I got about 10K ohms.
So where is the right place to measure the secondary coil resistance?
mydlyfkryzis
当有疑问时踢你的敌人在生殖器上，你可以道歉后
dumbkid said:
The points are the ground for the primary side. The 2 normal wires are 12V from battery (switched by ignition), the other is to the points which ground the coils primary side.
The High tension wire is High Voltage + on the secondary side, gets to ground by jumping across the spark plug gap.
Each condenser, besides absorbing the feedback from the primary side, when the magnetic field collapses, also supplies the connection to ground for the secondary side too. Once the spark is generated, the points close slightly later, and ground the coil primary, the secondary coil, and discharge the capacitor to make it ready for the next big event.
Condensers (capacitors) are interesting items. Steady 12V DC cannot pass through it, but the short pulse from the secondary see's it as a path to ground.
AC Volts pass capacitors, because they are essentially 120 pulses a second, reverse polarity with every other pulse. A capacitor can filter DC out of an A/C wire. A lot of devices use this feature, allowing a power DC source on a wire that also carries an AC signal. The correct side capacitor will filter out the DC, leaving only the signal.
bjbuchanan
New Member
Idk if you are still having the same issues but here is a simple answer
On your bikes your coils "ground" when the points close so there will be two wires,to and from them. one that supplies 12v power then one that goes to a respective point set. it grounds when the points close and touch, that's when you complete the circuit or flip the proverbial light switch
to measure low side. take the ohm setting on lowest setting(prob 200 ohm) and connect probes from 12v input to the outside of the coil( like a blue or yellow wire, something like that).
High side is measuring your plug wires. if they are screw in( prob not bc its a honda) you take your plug caps off and ram your plug leads home in to the plug wires. idk specific readings but it will prob be under 20k so thats where your meter should be
plug caps are diff. measure them separately and compare them to what your system is set up for, i.e. not to exceed like 10k ohms
On your bikes your coils "ground" when the points close so there will be two wires,to and from them. one that supplies 12v power then one that goes to a respective point set. it grounds when the points close and touch, that's when you complete the circuit or flip the proverbial light switch
to measure low side. take the ohm setting on lowest setting(prob 200 ohm) and connect probes from 12v input to the outside of the coil( like a blue or yellow wire, something like that).
High side is measuring your plug wires. if they are screw in( prob not bc its a honda) you take your plug caps off and ram your plug leads home in to the plug wires. idk specific readings but it will prob be under 20k so thats where your meter should be
plug caps are diff. measure them separately and compare them to what your system is set up for, i.e. not to exceed like 10k ohms
mydlyfkryzis said:
On a Magneto the pulses alternate positive to negative, because magnetos are AC devices - which is why you used to have to swap spark plugs round on multicyclinder magneto ignition engines so they'd wear evenly. On battery ignition the polarity doesn't change.
Whats happening is a coil tries to resist changes in voltage. When you contact the 12 volts to the coil, the windings try and resist the increase in voltage from 0 to 12. This is caused by the magnetic field that builds when the current starts flowing through the primary winding.
When you open the points, again the coil tries to resist the change in voltage and the collasping magnetic field generates a voltage to try and maint the level. Heres the funny thing - the voltage rises to around 200-300volts in the primary due to the number of turns in the coil, and this voltage is looking for somewhere to go. Because at that moment in time the points gap is still small (engines run in very very slow motion compared to electricity, the opening of the points is like watching paint dry to electrons!) it will arc arcoss them. This is where the condenser comes in, it wil soak away this 200 volts to earth (mostly) and reduce the arcing across the points.
I was doing some work on transistor ignitions last year and the same thing happens on these. The coil driving transistors have to have protection for spikes up to 400 volts (and the system I was working on 650) for exactly the same reason - when they shut off the earth path, the coil get mighty angry and sends a big pile of voltage by way of compliant!
