From what I can find out on the double marks with one retard for a H or M tractor. Looks like the double marks may have been originally intended to identify the TDC mark from the mark to grease the pilot bearing.
When IH got up to putting sealed pilot bearings in the front pulleys were changed to a single TDC mark for a while. But the 3 and 1 notch was used for a period until all of the 3 notches were used up.
When the pulley change was made IH started specifying for magneto timing. If 3 notches use the first of the double notches turning in normal rotation. If one notch set it at the TDC pointer compression stroke.
I'm leaning toward thinking the use of the retard mark for static timing is something passed down from mechanic to mechanic for safety when hand cranking was in use.
I could be wrong though, don't want to ruffle any feathers. Just like to figure out the straight of things. Just putting out ideas.
When IH got up to putting sealed pilot bearings in the front pulleys were changed to a single TDC mark for a while. But the 3 and 1 notch was used for a period until all of the 3 notches were used up.
When the pulley change was made IH started specifying for magneto timing. If 3 notches use the first of the double notches turning in normal rotation. If one notch set it at the TDC pointer compression stroke.
I'm leaning toward thinking the use of the retard mark for static timing is something passed down from mechanic to mechanic for safety when hand cranking was in use.
I could be wrong though, don't want to ruffle any feathers. Just like to figure out the straight of things. Just putting out ideas.
