George,
You were right in saying that I should check the odometer for accuracy before messing with the speedo drive pinion on the M41. I was quite sure the odometer was correct and that the fault was in the gear. Lousy mpg and a recollection (erroneous) of having tested it on a measured mile and coming up with about 1.15 miles indicated over that distance made me believe so. Yesterday as I was trying out my clutch adjustment, I decided to run the test again and, you guessed it, right on the nose. The same number on the white wheel came up every time I passed a mile marker. . . . ten times in a row. So, it's in the speedometer. Before pulling the one in the car, I experimented with a spare: spinning it with a drill in reverse at a constant speed. As I slacken the spring, the ribbon moves farther to the right. The opposite of what you said in our previous go around on this subject, but hey, who am I to nitpick. ;-) In fact, if I slacken the spring to the point where the roll comes just off its peg by itself, without spinning the input, I gain 10 mph. That's the maximum I can get out of it without showing too much red to the left while standing still, but that would be just enough if I can reproduce the effect on the speedo in the car. Thanks for pointing me in the right direction.
Bob S.