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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Points Ignition
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<blockquote data-quote="oexing" data-source="post: 137686" data-attributes="member: 1493"><p>A safe way to know what coil you can use in your system is to check the amps that go through the contact breaker. Obviously there must be a difference in ohms for 6 V or 12 V coils. But my bet is you can run a coil on your bike when current is well below 4 A , else the points will wear in no time. Capacitors are typically around 0.22 - 0.30 mF on all non-electronic ignitions. </p><p> As to excessive breaker wear today: What I miss on contact breaker systems is the grease/oil felt pad for cam lubrication. With car distributors old breakers were replaced at each maintenance and new Bosch grease applied to the cam. That was allright even for sixes and v-eights with only one breaker. So I don´t see a need for two sets for a twin, more hassles from that, just have two cams for one breaker at your specified firing angles, going with twin spark coils. </p><p> Once you got a grease felt there all should last for years on vintage bikes. But you defintely look for clean felt or dirt in it will produce a grinding paste on the cam. Lastly the cam has to be smooth and polished for minimum wear on the breaker heel. Fine wet´n´dry helps to keep the cam in shape and in case laser welding an very worn cam can restore it for decades of reliable operation. To be open, the most reliable ignition system seems to be the classic contact breaker coil setup, would not want to mess around with sophisticated electronics when a simple ATD is all you want. Magneto is quite good with rotating magnet, not the stone age rotating coil type with its trouble spots. Best design is one with ATD only on the breaker cam end like in Marellis, not in the Lucas drive end place. . The lasered cam below is from a Guzzi Falcone mag . The last photo shows ATD flyweights from a Vertex mag, no springs in the ATD, just a clever set of weights for a number of advance curves by selecting them. </p><p> Instead of messing around with old Lucas mags and D distributors no longer available I´d get a Saab distributor at € 50.- from Ebay, sense of rotation is the point for the ATD in it, and modify the cam for 50 degree v-twin. An adaptor for the engine case is no rocket science, a hub for the drive gear too. So then you get a good ATD, fat sparks, one breaker and easy timing.</p><p></p><p> Vic</p><p></p><p>Magneto Marelli cam:</p><p>[ATTACH=full]41451[/ATTACH]</p><p></p><p>Vertex mag ATD weights:</p><p></p><p>[ATTACH=full]41452[/ATTACH]</p><p></p><p>Vertex felt pad:</p><p>[ATTACH=full]41453[/ATTACH]</p><p></p><p>Saab distributor:</p><p>[ATTACH=full]41454[/ATTACH]</p><p></p><p>[ATTACH=full]41455[/ATTACH]</p></blockquote><p></p>
[QUOTE="oexing, post: 137686, member: 1493"] A safe way to know what coil you can use in your system is to check the amps that go through the contact breaker. Obviously there must be a difference in ohms for 6 V or 12 V coils. But my bet is you can run a coil on your bike when current is well below 4 A , else the points will wear in no time. Capacitors are typically around 0.22 - 0.30 mF on all non-electronic ignitions. As to excessive breaker wear today: What I miss on contact breaker systems is the grease/oil felt pad for cam lubrication. With car distributors old breakers were replaced at each maintenance and new Bosch grease applied to the cam. That was allright even for sixes and v-eights with only one breaker. So I don´t see a need for two sets for a twin, more hassles from that, just have two cams for one breaker at your specified firing angles, going with twin spark coils. Once you got a grease felt there all should last for years on vintage bikes. But you defintely look for clean felt or dirt in it will produce a grinding paste on the cam. Lastly the cam has to be smooth and polished for minimum wear on the breaker heel. Fine wet´n´dry helps to keep the cam in shape and in case laser welding an very worn cam can restore it for decades of reliable operation. To be open, the most reliable ignition system seems to be the classic contact breaker coil setup, would not want to mess around with sophisticated electronics when a simple ATD is all you want. Magneto is quite good with rotating magnet, not the stone age rotating coil type with its trouble spots. Best design is one with ATD only on the breaker cam end like in Marellis, not in the Lucas drive end place. . The lasered cam below is from a Guzzi Falcone mag . The last photo shows ATD flyweights from a Vertex mag, no springs in the ATD, just a clever set of weights for a number of advance curves by selecting them. Instead of messing around with old Lucas mags and D distributors no longer available I´d get a Saab distributor at € 50.- from Ebay, sense of rotation is the point for the ATD in it, and modify the cam for 50 degree v-twin. An adaptor for the engine case is no rocket science, a hub for the drive gear too. So then you get a good ATD, fat sparks, one breaker and easy timing. Vic Magneto Marelli cam: [ATTACH type="full"]41451[/ATTACH] Vertex mag ATD weights: [ATTACH type="full"]41452[/ATTACH] Vertex felt pad: [ATTACH type="full"]41453[/ATTACH] Saab distributor: [ATTACH type="full"]41454[/ATTACH] [ATTACH type="full"]41455[/ATTACH] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Points Ignition
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