[Pinaddict00]

I know this topic is regularly beaten to death, but I have a 2000 400 ex and all I have is a uni filter with stock exhaust. The previous owner tells me it has a bigger piston in it but can't remember what it is? Lol. So I'm wondering if it needs to be jetted at all I plan on going to tall pines in new York in a week and there is lots of mud so I want to run the air box lid. Is it safe to keep it the way it is with stock jets or should I go up at all?

 

[retro]

I'd try setting it up like you intend to run it next week and see what happens. If it doesn't feel quite right take spark plug readings and fine tune. Have fun!

 

[SamUK]

Retro is right, spark plug readings will tell a lot. There’s a few guys on here who are spot-on at Reading plugs, you couldnpost those pics of you get stuck.

 

[Pinaddict00]

Thanks, I'm pretty new to atvs in general and for sure new to jetting a carb. I just don't want to damage the motor in any way while riding. Does anyone know of a link to pictures of plugs being to lean or rich?