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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Advance
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<blockquote data-quote="oexing" data-source="post: 128874" data-attributes="member: 1493"><p>All that talk about detonation - and then using 91 octane fuel - now I try to see the logic ?? So why have they come upon 98 or 100 octane fuel or avgas that had still higher octane rating in the past ? </p><p> There could be some truth about detonation in this engine which wrecked the piston ring. But then why on earth keep using 91 octane fuel at all ? </p><p>Also I´d like to see the advance curve of the ATD in this case. No use stating advanced and retarded degrees when not telling at which speed you have full advance. I´d like to have full advance NOT before 3000 rpm crank speed, maybe 3500 better. And mixture seems very rich, could lead to thinned oil from that, no great lubrication then. Some more photos of piston crowns would be good for drawing conclusions and to learn from. For knowing about mixture you´d better look at the piston or spark plug thread face, not the ceramic. Black sooty deposits are very rich , so go for the carby. When that is fixed you pick any spark plug that keeps the ceramic nice and bright - and this depends on your riding style, pottering or high speed motorway burns - very different conditions for plugs. </p><p> As long as you see a sooty piston crown I cannot believe in overheating effects , you´d have non deposits in that case but melted edges or worse. I remember one story decades ago with an all iron HD Sportster of my neighbour , got a holed piston from using "regular fuel" then because the guy from the filling station suggested to save the money by not having high octane fuel.</p><p></p><p> Vic</p></blockquote><p></p>
[QUOTE="oexing, post: 128874, member: 1493"] All that talk about detonation - and then using 91 octane fuel - now I try to see the logic ?? So why have they come upon 98 or 100 octane fuel or avgas that had still higher octane rating in the past ? There could be some truth about detonation in this engine which wrecked the piston ring. But then why on earth keep using 91 octane fuel at all ? Also I´d like to see the advance curve of the ATD in this case. No use stating advanced and retarded degrees when not telling at which speed you have full advance. I´d like to have full advance NOT before 3000 rpm crank speed, maybe 3500 better. And mixture seems very rich, could lead to thinned oil from that, no great lubrication then. Some more photos of piston crowns would be good for drawing conclusions and to learn from. For knowing about mixture you´d better look at the piston or spark plug thread face, not the ceramic. Black sooty deposits are very rich , so go for the carby. When that is fixed you pick any spark plug that keeps the ceramic nice and bright - and this depends on your riding style, pottering or high speed motorway burns - very different conditions for plugs. As long as you see a sooty piston crown I cannot believe in overheating effects , you´d have non deposits in that case but melted edges or worse. I remember one story decades ago with an all iron HD Sportster of my neighbour , got a holed piston from using "regular fuel" then because the guy from the filling station suggested to save the money by not having high octane fuel. Vic [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Advance
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