AJS & Matchless Owners Club

If the clutch handlebar lever is 5" long from tip to pivot bolt and the distance from pivot bolt to nipple centre is 7/8" (0.875") the mechanical advantage is 5.7 to 1 (5 divided by 0.875).

If the pivot bolt to nipple centre is 1 1/8" (1.125") with the same length lever the mechanical advantage is only 4.4 to 1. (5 divided by 1.125) which is 23% less advantage than the 7/8" example.


Above lever length of 5" used for explanation only. Obviously finger effort occurs not at the lever tip but at some point midway between the lever tip and the pivot bolt.
If the finger effort is applied say, halfway between the tip and pivot bolt (at 2.5"), the mechanical advantages would be 2.86 (2.5 divided by 0.875) and 2.22 (2.5 divided by 1.125), but still 23% less advantage than the 7/8" lever.

I have to say thank you all very much for a comprehensive set of answers. I have to admit that my top-of-head calculation was the same as Rob's in terms of calculating to moment of force at the nipple, but thank you, Spriddler, for putting me right!