[WisconsinMax]

Hi new here but not to forums. Just picked up an 02 400EX with an exhaust and air filter and seems to run great. I did the normal stuff as soon as I got it. Changed the oil and oil filter and put a new spark plug in. First question is it seems to idle a little high sometimes but that doesn't bother me a whole lot. What I noticed today was oil seeping by a gasket and little air bubbles coming out when I shut it off. Need your help on what you think it could be. Thanks

 

[WisconsinMax]

 

[Here 2 help]

This is the head gasket leaking. It needs to be replaced.

 

[WisconsinMax]

Thanks! This an easy fix? I'm fairly handy but never wrenched on a atv before.

 

[yellowex]

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

 

[Here 2 help]

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 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.

 

[Here 2 help]

Thanks! This an easy fix? I'm fairly handy but never wrenched on a atv before.

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 luck