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Advance/retard wheel on dizzy


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If it is a Lucas original then I believe 11 clicks of the serrated wheel equals 1 degree.  The modern replica distributors may have a different number of serrations on the wheel and a different thread on the shaft, so that probably won't be right for them. 

There should be a series of graduations visible on top of the vacuum unit behind the diaphragm housing. Those are 4 degrees each. 

Edited by RobH
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1 hour ago, RobH said:

If it is a Lucas original then I believe 11 clicks of the serrated wheel equals 1 degree.  The modern replica distributors may have a different number of serrations on the wheel and a different thread on the shaft, so that probably won't be right for them. 

There should be a series of graduations visible on top of the vacuum unit behind the diaphragm housing. Those are 4 degrees each. 

The disy  specs usually refer to disy degrees, so crank degrees are double.

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The info I was quoting says those are crank degrees Peter.  

Edited by RobH
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8 minutes ago, RobH said:

The info I was quoting says those are crank degrees Peter.  

OK Rob.

In  the past Ive been caught out by the bible and this page, until I spotted the small print in blue: http://www.teglerizer.com/mgstuff/advance_curves.htm

Peter

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40 minutes ago, ed_h said:

I think the fineness of the serrations on the wheel may be different than Rob's. 

Yes I wonder whether there was much consistency in the serrations over time.  I doubt the clicks were supposed to be the calibration - that was why there were graduations provided on the shaft. 

Edit:

I've just been out and measured a DM2. It's difficult to tell exactly because the graduations are quite wide but as best as I can tell there are 42-45 clicks per graduation division of 4 degrees. That makes near as dammit 11 clicks per degree, at least for that particular dizzy.  

Edited by RobH
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