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RE: condenser and points
Posted by : Fuzz Ashford Kent (86.14.252.127) 
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On Sunday 09/12/12 at 01:52:41
The cam needs to open the points gradually to prevent float. This causes a big problem when it comes to breaking the primary circuit. Think of the points as a little 4 amp arc welder. When arc welding, you touch the electrode to your work piece, to start current flowing, and lift it up to get an arc gap. The constant current power source of the arc welder will increase the voltage to the electrode to maintain the current flow across the arc. If you keep lifting the electrode you will reach a point where the welder can not supply enough voltage to maintain the arc and current flow will stop. Points will do the exact same thing. Current flows through them when they close. When they open the inductance of the ignition coil tries to maintain that current so an arc will be struck between them until the points open up enough to break the circuit. The more current you run through the points, the harder it is for them to break the current. That is why point systems have a condenser (called a capacitor in any other electrical system). The condenser slows down the reaction time of the coil to allow the points time to open and break the circuit. Without a condenser you will likely never break the primary current and get no spark from the secondary. Having a condenser that is too large will completely prevent arcing across the points but will also slow the coil so much that it is unable to strike an arc on the secondary. The trick is to find a condenser that gives a happy medium between the arc at the points and the arc at the spark plug. A smaller condenser means more power from the coil but shorter point life due to pitting. A larger condenser will give you longer point life but sacrifice coil output. One trick to make a high performance points system is to wire two condensers together in series. This effectively gives you one condenser with half the value. Most guys when changing points will replace the condenser if it needs it or not. This is not always a good idea. A condenser is a simple component and they rarely go bad. The only bad condenser I've seen was brand new, the wire had broken off inside. If you are changing your points and the motor was running fine then do not replace your condenser. You may do more harm than good. 
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