OK, here are the instructions on how to use the Ignition Timing Conversion Chart. First of all you must remember that all the information is in inches.
The chart is produced in M/S Excel format and it contains hidden formula. This allows you to change certain data for different engines and the chart will automatically calculate the distance before top dead centre at all the degree readings.
At the top of the chart the Rod Length reads 6.000 and as the A10 rod length between the centre of the big end bearing and the centre of the little end bearing is 6.469inches, change the 6.000 to 6.469.
Next the Stroke reads 2.568 and the A10 stroke is 3.307inches so again, change the 2.568 to 3.307.
Please note that these figures ar for the A10. The A7 conrod length is 6.000 and the stroke is 2.858.
Every time you change one of these figures
and move the curser to another cell all the figures under the word Linear will change automatically. These figures are the distances in inches BTDC compared to the degrees that are listed to the left of the Linear measurements. These, of course, range from 0 to 179 throughout the chart.
To help convert these distances in decimal inches to fractions, here are the more common measurements given for A7 and A10 machine ignition timing.
5/16 = 0.3125" 11/32 = 0.344" 3/8 = 0.375" 13/32 = 0.406"
So if your bike should be timed at 5/16btdc, add the relevant dimensions for rod length and stroke then read the chart where it says 0.3125 (or nearest) and whatever number is to the left of this figure is the equivalent number of degrees btdc.
I hope that I've managed to explain it OK.
Beezageezauk.
