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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
600cc Comet Carbie?
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<blockquote data-quote="Simon Dinsdale" data-source="post: 77514" data-attributes="member: 58"><p>What I found a few years ago is that for easy starting you need you ignition to be around 4 - 6 degrees before TDC fully retarded. This is the same single plugs or two plugs per cylinder. On a road going bike with a kickstart anything greater will kick back and anything less gets harder to start. On racing machines it doesn't matter as rollers are usually used to start them.</p><p> The problem is with specials, twin plugs etc you usually need to retard the fully advanced figure from the factory 36 - 38 degrees to what you are running which is 26 degrees fully advanced. With ignition systems the advance range is usually fixed to a set range and so when you reduce the fully advanced figure you also reduce the fully retarded figure. </p><p>On a new BTH you can only select and set the fully advanced position. You then need to measure the fully retard position when running which is not easy to do but there was a timing disc been made a few years ago that allows a strobe to be used which fitted in the big end quill and still provided an oil flow. My bet is you are trying to start the bike with a fully retarded ignition timed at tdc or even worst after tdc and ideally need an ignition system with a reduced advance range. On coil ignition or magneto it's easy as you just add weld to the ears of the mechanical advance device to reduce the range. On anything electronic you need the manufacturer to make a special unit to suit your requirement.</p></blockquote><p></p>
[QUOTE="Simon Dinsdale, post: 77514, member: 58"] What I found a few years ago is that for easy starting you need you ignition to be around 4 - 6 degrees before TDC fully retarded. This is the same single plugs or two plugs per cylinder. On a road going bike with a kickstart anything greater will kick back and anything less gets harder to start. On racing machines it doesn't matter as rollers are usually used to start them. The problem is with specials, twin plugs etc you usually need to retard the fully advanced figure from the factory 36 - 38 degrees to what you are running which is 26 degrees fully advanced. With ignition systems the advance range is usually fixed to a set range and so when you reduce the fully advanced figure you also reduce the fully retarded figure. On a new BTH you can only select and set the fully advanced position. You then need to measure the fully retard position when running which is not easy to do but there was a timing disc been made a few years ago that allows a strobe to be used which fitted in the big end quill and still provided an oil flow. My bet is you are trying to start the bike with a fully retarded ignition timed at tdc or even worst after tdc and ideally need an ignition system with a reduced advance range. On coil ignition or magneto it's easy as you just add weld to the ears of the mechanical advance device to reduce the range. On anything electronic you need the manufacturer to make a special unit to suit your requirement. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
600cc Comet Carbie?
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