advance/retard checking

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PeterSE6a
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advance/retard checking

Post by PeterSE6a » Fri Mar 22, 2019 7:49 pm

Hi I have timed my 6a with a stroboscope , is there a way of checking with the strobe the vacuum advance retard and the bob weight advance retard . When I checked the timing the light point moved to the left when I revved the engine , then settled back to the proper strobe mark on tick over , was that the vacuum advance/retard ? The strobe method was as described in the RSSOC special Workshop Manual , thanks . :D


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advance/retard checking

Post by rebel alliance » Fri Mar 22, 2019 8:54 pm

I'm guessing but if you removed the vacuum pipe would you only get the bob weight advance degrees...



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Old and Slow
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advance/retard checking

Post by Old and Slow » Fri Mar 22, 2019 8:59 pm

Also, the vacuum tends to be active when the throttle closes (on over-run etc, to advance the ignition when the mixture is rich and takes longer to burn - helps stop the popping and banging); when the throttle is open wide there's very little vacuum.
Therefore if you open the throttle to increase the revs, as Rebel Alliance says, you are mostly seeing the effects of the bob-weights.


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Roger Pennington
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advance/retard checking

Post by Roger Pennington » Sat Mar 23, 2019 7:41 pm

As has been said, with the vacuum pipe disconnected and plugged, you should only see centrifugal advance when you rev the engine, and you can then check it against the book figures.
If you have access to a Mityvac (or similar) vacuum tester/brake bleeder, (with a gauge), then you can connect it to the vacuum advance capsule on the dizzy and apply specific amounts of vacuum, and see if the amount of advance that you get corresponds to the vacuum advance curve in the book.


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