Can someone give me a measurement on a spark plug wrench please? Hi guy's, I've not long been the owner of a nice 2003 400S, which came to me with no tool kit. What I need for her is a spark plug socket / wrench, and also some information, like are they special as per my other squeeze the XR400, which needs to be thin enough to get down the tunnel. Therefore I need to know the overall length, and also what size, eg:- 16 mm 18 mm etc. Thanks in advance, Mark.