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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin coil
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<blockquote data-quote="Pete Appleton" data-source="post: 11667" data-attributes="member: 145"><p><strong>Wasted spark</strong></p><p></p><p>A single coil with two outputs is used on many vehicles that have electronic ignition. This system is called 'wasted spark' for obvious reasons.</p><p></p><p> On an in-line engine the wasted spark occurs on the other cylinder just as the inlet valve is about to open for the overlap period. On a 'V' twin the wasted spark from the firing of the front cylinder occurs 20 degrees or so into the induction stroke of the rear cylinder with the inlet valve well open. You might think that this would cause a pop back through the carb, but it doesn't. The Pazone and Boyer Bransden electronic ignitions supplied for Vincents use wasted spark with no ill effects.</p><p></p><p> The only thing to watch out for is that you don't fit a coil intended for electronic ignition to a contact breaker system as they are very low resistance (typically less than 0.5 Ohms) This will melt the contact breakers and the long 'points closed' periods will destroy the coil within seconds. For contact breaker type systems you will need a coil of about 5 Ohms.</p><p></p><p> The idea of using twin points may need some careful thought as you will have to ensure that there is at least one set of points open at all times or you won't get it to fire when you want it to</p></blockquote><p></p>
[QUOTE="Pete Appleton, post: 11667, member: 145"] [b]Wasted spark[/b] A single coil with two outputs is used on many vehicles that have electronic ignition. This system is called 'wasted spark' for obvious reasons. On an in-line engine the wasted spark occurs on the other cylinder just as the inlet valve is about to open for the overlap period. On a 'V' twin the wasted spark from the firing of the front cylinder occurs 20 degrees or so into the induction stroke of the rear cylinder with the inlet valve well open. You might think that this would cause a pop back through the carb, but it doesn't. The Pazone and Boyer Bransden electronic ignitions supplied for Vincents use wasted spark with no ill effects. The only thing to watch out for is that you don't fit a coil intended for electronic ignition to a contact breaker system as they are very low resistance (typically less than 0.5 Ohms) This will melt the contact breakers and the long 'points closed' periods will destroy the coil within seconds. For contact breaker type systems you will need a coil of about 5 Ohms. The idea of using twin points may need some careful thought as you will have to ensure that there is at least one set of points open at all times or you won't get it to fire when you want it to [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin coil
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