[72SB]

How many teeth and what size is the speedo drive gear ?

8, large?

I was switching from a 21 tooth "driven" gear to a 20 tooth, didn't work. I assume the 20 is to small for the drive gear. The 21 tooth works but I am a few MPH off on speedo so a 20 should be right

it had a 23 tooth driven but I put on larger tires