Ignition Timing Chart for Puch

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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.


Puch timing chart.jpg


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