Re: Boyer ignition problem

Posted by hendred on Nov 19, 2020; 12:40pm
URL: http://silk-motorcycles.221.s1.nabble.com/Boyer-ignition-problem-tp5001882p5002082.html

I haven't measured the advance the mechanical unit provides and I don't really want to take it all apart again at the moment.  Looking at pictures of it I would estimate about 15 degrees but could be very wrong.  I asked Boyer Bransden for the technical details of the Micro Digital box developed for the Silk and they very kindly sent back the information requested.  The Boyer Silk box gives 20 degrees advance starting at 1000 rpm and reaching full advance at 4000 rpm. There is only a very slight increase in advance between 3000rpm and 4000rpm so essentially it reaches full advance by 3000rpm.  It also has no significant advance up to 1000rpm.  Assuming the measured and calculated figures are correct, full advance for 0.2" is 27 degrees and 0.3" is 34 degrees, then the starting advances are 7 degrees and 14 degrees respectively. Pretty similar to the mechanical advance if 15 degrees is correct.

I found the standard Norton Boyer Micro Digital advance curve here:

https://www.accessnorton.com/NortonCommando/electronic-ignition-advance-curves.21964/   

Look for the Rick in Seattle curves.  The data here is for engine advance for a camshaft rotating at half engine speed so everything has to be halved for a Silk installation. This gives 16 degrees advance at 2500 rpm.  The interesting thing about the standard Norton curve is the increase advance at 500 rpm for idle stabilisation.  This won't help with kickback on starting a Silk.
Hope this answers some of the questions.