What size is the sparkplug on a 400EX. I lost that came with it.Every one I try is either to big to fit in the little space to get to it or it's to small to fit the plug.

Thanks for the advice with the lowering kit. Everything worked out fine.

 

I am justing that what you want to know is what size socket that you can use to get the plug out? I think that it is an 18mm, but that will not do you any good. The space is so small in the plug hole that a socket will not fit in. You must find or use the a special plug wrench and it has to be long because of how deep the hole is. Sorry for the bad news if this is what you are asking.

 

a socket will to fit! i just took my plug out today with a socket so believe me one will fit as long as you have the right size. i used 11/16 size socket