Re: Ignition Timing

Posted by hendred on May 29, 2020; 10:00am
URL: http://silk-motorcycles.221.s1.nabble.com/Ignition-Timing-tp5001920p5001922.html

Apologies for the confusion.  My static timing is 5mm or 0.2" btdc.  Set statically as per the handbook it results in a running advance about 3 - 4 degrees retarded when checked with a strobe. I think it must be because of wear/backlash in the mechanical advance unit.  I made the strobe marks on the alternator stator by setting the piston on the correct advance using a dti down the plug hole.  There are two convenient lines cast into my alternator rotor.  I also marked tdc on the stator as well.  

On starting the engine the strobe showed the static setting of the timing resulted in a retarded ignition timing when running.  I advanced the Lumention back plate to give the correct strobe setting when running.

I didn't measure the degrees of advance using a disc.  Using the Torqsoft program I get 27.14 degrees for 5mm (0.2") advance and 33.73 degrees for 7.64mm (0.3") advance. 27 degrees and 34 degrees for practical purposes.  From my recent experience I will set the timing using piston position and strobe, using the handbook method for getting an approximate initial setting.

Unless you have the handbook supplied with the  bike I don't know how you can tell which advance setting to use.  I think all the 38mm carb bikes are 5mm.  Hopefully somebody will come along with a definitive answer.