I want to put some holes in my airbox lid and someone said i should rejet. How do i do it? THanks in advance for any help.

 

Go here:

https://atvconnection.com/Department...?advsearch=Yes

Then select 'all models' and 'carburetion/jetting.' You will learn all you need to know. There's plenty to read, but lots of the posts completely outline the jetting process.

ogre

 

HondaEX400,
I haven't looked at the site Ogre suggested, but I've written a fairly explicit & easy to follow article on rejetting. It's the system I've used for many years and can be applied to bikes or quads.
If you'd care to have the file, email me for it.