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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Poor starting on new Amal and BTH Magneto
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<blockquote data-quote="davidd" data-source="post: 42132" data-attributes="member: 1177"><p>It is a great question. I have wondered about it myself, but I did not have enough time to answer it during the racing season. You can get the BTH as fixed, but I did not. When on the dyno I kept advancing it a few degrees at a time and it kept making more power. I reached the end of the slotting on the magneto body and had no Idea where the timing had ended up. I took the bike home and re-indexed the mag, but before doing so I strobed it to see where the timing was. It was at 19. I asked my friend, who was holding the strobe, to check the advance. He said it was not changing. To this day I do not know if I was just not letting the revs drop low enough or if my friend was not noting the change. With races coming up and no discernable problem, I stopped looking for answers.</p><p></p><p>I should also say that I was also busy figuring out how to time the BTH properly. I noticed that with the pin through the hole that marks the sparking point that I could move the crank 4.5 degrees in either direction. So I spent some time finding out with the strobe exactly where the spark occurred. It turns out that the spark occurs when the pin is inserted and then the crank is rotated 4.5 degrees in the direction of rotation. So, on my BTH, when the pin is tight in the direction of rotation, that is where the spark occurs.</p><p></p><p>So, I will have to check it again to see about the advance, but I think using a strobe is worthwhile as a check.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 42132, member: 1177"] It is a great question. I have wondered about it myself, but I did not have enough time to answer it during the racing season. You can get the BTH as fixed, but I did not. When on the dyno I kept advancing it a few degrees at a time and it kept making more power. I reached the end of the slotting on the magneto body and had no Idea where the timing had ended up. I took the bike home and re-indexed the mag, but before doing so I strobed it to see where the timing was. It was at 19. I asked my friend, who was holding the strobe, to check the advance. He said it was not changing. To this day I do not know if I was just not letting the revs drop low enough or if my friend was not noting the change. With races coming up and no discernable problem, I stopped looking for answers. I should also say that I was also busy figuring out how to time the BTH properly. I noticed that with the pin through the hole that marks the sparking point that I could move the crank 4.5 degrees in either direction. So I spent some time finding out with the strobe exactly where the spark occurred. It turns out that the spark occurs when the pin is inserted and then the crank is rotated 4.5 degrees in the direction of rotation. So, on my BTH, when the pin is tight in the direction of rotation, that is where the spark occurs. So, I will have to check it again to see about the advance, but I think using a strobe is worthwhile as a check. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Poor starting on new Amal and BTH Magneto
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