Ignition Timing Chart for Puch
Here is a handy chart for converting Puch ignition timing from degrees before top dead center to millimeters before top dead center and vice versa.
This can be calculated from basic trigonometry.
L = conrod length (in mm) - usually it's a little more than twice the stroke. Puch is ~90mm
a = crank effective radius, which is 1/2 the stroke. for puch, stroke = 43mm, a=21.5
then a*cosΘ plus the square root of ( L^2 + (a*sin Θ)^2) gives you the height h (shown in pic)
and if conrod length (L) plus crank radius (a) is height (h) at TDC, just subtract that value from your calculated h, and you have mm BTDC
[(a*cosΘ) + sqrt( L^2 + (a*sin Θ)^2)] - (L+a) = mm BTDC for given degree Θ
- make sure you're consistent using radians or degrees, or if needed convert degrees to radians:
radians = (degrees / 180)*pi