I've always used 7/16" but since I adopted that figure ethanol has been added to the petrol and I continue with it because my timing stick is still marked that way.spookefoote1956 wrote:I notice that young Spriddler has suggested in other posts 7/16" btdc due to modern fuels. How do you feel about this?
From a purely practical point of view, bearing in mind parallax effect when sighting the stick in the plug 'ole', plus the fact that you may not be holding the stick vertical, plus the stick may slip between measurements on a domed piston, plus backlash in the timing gears and mag chain, plus it may move a tad when you tighten the mag sprocket (need I go on?) so if you can set the timing precisely within 1/8" (e.g. exactly 7/8" or exactly 1/2") you'll be a better man than I, Gunga Din Anywhere between the two figures will be O.K. Treat it as a target!
I time mine with the h/bar A/R lever not quite at full advance then if, on a test ride it seems slightly too retarded or too advanced I can always ease the h/bar A/R lever a smidge temporarily until I can be ars*d (or not) to retime th'engine at the mag. In my experience there's always more movement at the h/bar lever than is needed to move the mag plate from full advance to the starting retard position. In any case I have never needed to fully retard the h/bar lever.
Other, less slapdash opinions are available.