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JCSinPITTS,PA 
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Joined: 14 Sep 2009
Points: 240
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 Topic: Magneto Impulse Questions
Posted: 21 Feb 2018 at 5:32pm |
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I have a question..... how do you KNOW you have a 30% lag impulse? and on AC - B do I time it idleing or at half throttle? and which mark do I time it to? It seems so simple yet when I review old posts there are a lot of differing opinions!
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Dakota Dave
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Joined: 12 Sep 2009
Location: ND
Points: 3971
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Posted: 21 Feb 2018 at 5:44pm |
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its a 30 Deg. lag on the impulse mag. the impulse only operates below 200 rpm. time it a idle. Time it to the F mark when running If its an airplane Mag it could be either 25 Deg. or 18 Deg. the deg lag on the mag doesn't make any difference on the engine when running. a distributor has advance weights so needs to be above 1/2 throttle to check timing with timing light.
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Hubnut
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Joined: 30 Jul 2014
Location: Gainesville, FL
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Posted: 21 Feb 2018 at 5:59pm |
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I always thought the lag was built-in to the mag. If you time to the FIRE mark, everything should be just fine. I just did one this past weekend with a timing light. Boy, you think you can hear when it's timed properly. I timed it by ear, then put the light on it. I couldn't even see the FIRE mark! I got it just right with the light. Never trust your ears--or at least mine.
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1940 B "Lucy"
1941 B w/ Woods L59 "Flavia"
1942 B w/ finish mower "Dick"
1941 C w/ 3-point "Maggie"
1947 C SFW w/ L306 "Trixie"
1972 314H
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CTuckerNWIL
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Joined: 11 Sep 2009
Location: NW Illinois
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Posted: 22 Feb 2018 at 11:40am |
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Static timing is done with the C or TDC mark. With the engine running at proper rpm, the fire mark is used with a light.
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HoughMade
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Joined: 22 Sep 2017
Location: Valparaiso, IN
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Posted: 22 Feb 2018 at 11:43am |
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Static time to "Center", get it running, then at about 1/2 throttle or above, tune by ear or with a timing light to "Fire".
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1951 B
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