Rev counter problem

[royb]

When I kick the bike over the rev counter needle goes to about 4 - 5, kick again & it goes up to 7 - 8, then well into the red (where I stopped!), the needle very slowly drops back to zero.

I'm assuming the mechanism is a bit sticky (possibly through lack of use?), not ever come across this before so is this an easy fix?

cheers
Roy