ignition puzzle

[roger.h]

I'm sure some boffin will know,--when a plug oils up when starting cold----If I pull off the ignition lead and make the spark jump between lead and plug top----Why does the faulty plug now start firing and after a short while I can reconnect the lead onto the plug??
It seems that the power to the plug is enhanced allowing the plug to "self clean?" would a better coil help? ( I have Aldon ingnition) Thanks Roger.h

[types26/36]

By making the spark jump a gap it increases the intensity of the spark ..(higher voltage?) I think but I'm sure the sparkies among us will know, I remember years ago there used to be a device sold that was fitted in the HT cable that had a small gap built into it, it was suppose to give a nice big spark.....always thought it sounded like a gimmick to me
If your ign system is in good condition it should be fine although a sports coil may help under certain conditions....you could also try hotter spark plugs but are you sure you are not just trying to treat the symptoms rather then effect a cure? is the engine in good condition ....compression...rings...pistons...guides...is it using oil?
PS welcome to the forum Roger.

[bob_rich]

Hi Roger

Yes putting a gap in an ignition lead does frequently result in a improve spark. The coil voltage has to rise to break the external gap over and this then puts the full ( and somewhat higher) voltage on the spark plug far more rapidly than the coil alone could. The spark energy will increase up to a point because the stray capacitance of the coil and the spark plug leads will charge to a higher voltage and thus store more energy. This only works up to a point though as the available energy is limited by the coil design and the current in the coil. This method increases the voltage seen by the coil and secondary its winding and may increase the voltage across the points, points capacitor ( condenser) and or the transistor in the ignition module if electronic ignition is used. Motor bikers used to use a device called a Norton Converter and I am told one could be made easily by cutting the ignition lead and putting the wires about 1/4" apart usually using a button to set the gap.

these days an external spark could increase radio interference effect quite a bit

question is why are the plugs fouling up?

Best of luck

Bob

[twincamman]

The distance from the wire to the plug increases the resistance and so at the gap on the plug ----R=E overI -----e

[roger.h]

There you are-----I knew there would be somebody who knew the answer! Thanks. Actualy the engine is not in bad condition (about half worn), but cannot fit a sports coil with Aldon ignition. Pal of mine didn't read the instructions and blew up his ?90 conversion unit! Roger h