is ther a 3:1 ratio speedo or has my bike got the wrong  speedo gear on frount wheel ?

any one know much about  speedo drives etc.

my speedo is out  so i turned the frount wheel 1 full turn and the cable turned 3 full turns  and my speedo it a 2:1 ratio speedo  im thinking if you cant get a 3:1 speedo my  cable drive on the frount wheel may have been replaced with the wrong one at some stage maybe the one for a bigger  wheel was used as my wheel is 16 inch or wrong cable  maybe as the bottom half of cable has a worm drive type gear on it wrong cable may have been used..

any one got ant ideas or thoughts on this??

ok thanks for the reply  im thinking ive got a 21inch drive on my 16inch wheel ill try change that first.

see how i go