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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Timing & modern Fuel
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<blockquote data-quote="Simon Dinsdale" data-source="post: 47280" data-attributes="member: 58"><p>The original Lucas atd was designed to have 17 degrees movement giving 34 degrees at the crank. The original timing was 38 before fully advanced giving 4 btdc fully retarded. </p><p></p><p>My twin still uses an atd. A few years ago the bike was getting harder to start. On checking the timing it was set to 34 degrees fully advanced but when I checked the retard figure it was 3 degrees AFTER tdc due to wear in the atd. </p><p>I fitted a new Roy Price atd which measures at 15 degrees movement. This allowed me to set the fully retarded timing to 4 degrees btdc and thus fully advanced at 34 degrees. The starting was greatly improved.</p><p></p><p>Another thing is be carefully bending the ears on the atd. The new Roy Price atd's use a thicker material, but I have seen original Lucas atd's with broken off ears which were of a thinner material. When you bend the ear you change the contact area on the ear from an full height contact to a point contact which by nature of the direction you bend it will be at the furthest point (which is bad from a mechanical point of view) from where the ears break off.</p></blockquote><p></p>
[QUOTE="Simon Dinsdale, post: 47280, member: 58"] The original Lucas atd was designed to have 17 degrees movement giving 34 degrees at the crank. The original timing was 38 before fully advanced giving 4 btdc fully retarded. My twin still uses an atd. A few years ago the bike was getting harder to start. On checking the timing it was set to 34 degrees fully advanced but when I checked the retard figure it was 3 degrees AFTER tdc due to wear in the atd. I fitted a new Roy Price atd which measures at 15 degrees movement. This allowed me to set the fully retarded timing to 4 degrees btdc and thus fully advanced at 34 degrees. The starting was greatly improved. Another thing is be carefully bending the ears on the atd. The new Roy Price atd's use a thicker material, but I have seen original Lucas atd's with broken off ears which were of a thinner material. When you bend the ear you change the contact area on the ear from an full height contact to a point contact which by nature of the direction you bend it will be at the furthest point (which is bad from a mechanical point of view) from where the ears break off. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Timing & modern Fuel
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