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Are you saying advance has been disabled on your distributor, or just that you contemplate it?
In a nutshell, the reason for advancing the timing with increased engine speed is to start the ignition process (which takes a certain time to finish in the cylinder, it is not instantaneous) at such a piston position that by the time combustion reaches maximum force, the piston is on its way down and you get maximum energy to the crankshaft. Start it too soon, and you get force opposing the direction of engine rotation because the piston is still moving upward. Start it too late, and the piston is so far on its way down that combustion force is inefficiently transmitted and power is lost. So the faster the engine runs, the sooner in the cycle you need to start combustion with a spark.
Unless an engine runs at a fixed speed all the time, the idea of eliminating ignition advance is ridiculous.
I am not much familiar with Saab 2-strokes so don't know if they all had mechanical advance only or not. Unless your engine is modified, there is probably nothing to be gained by any alteration of distributor adjustments from the factory settings.
Variations in fuel quality may justify slight alteration from factory settings for optimum operation. This would be a matter of trial-and-error on your particular engine and best done on a dynamometer. Short of that, it will run fine on today's gas at factory settings, and far better than it ever will with all advance disabled.
Principles of 2-stroke timing may vary slightly from 4-stroke, I do not know, but any differences are in fine details not the big picture. See the link for some discussion, and google for lots more.
posted by 75.147.23...
http://www.dragonfly75.com/motorbike/timingcurves.html
, Wed, 22 Apr 2015 08:46:42
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