You need a thin walled 18mm spark plug socket. There's one in the tool kit that came with the machine or you can get one from a reputable repair shop.Hello,
I just bought a 2001 400ex and i went to change the spark plug, but i couldnt figure out the hex size. Is there a special tool i need to buy??? Any help would be greatly appreciated.
-Thanks in advance
You will need a service manual and plan on about 4 hours to do the job. I recommend when you do it to replace the piston rings. Now, unless you know the history of the machine, you need to take it apart first to find out the brand and size of piston in it before ordering parts. Take your time, follow the service manual instructions and you should be able to do it. The hardest part of the job will be cleaning the gasket surfaces in preparation for the new gaskets. Good luckThanks! This an easy fix? I'm fairly handy but never wrenched on a atv before.