New Guy

[eburns631]

I just recently bought an 07 400ex. At the moment it is completely stock. However, I am looking at buying a yoshi rs2 slip on as well as a k&n filter. I was wondering what would be the best way to jet my quad afterwards and where to buy/how to install them. Thanks

[CJM]

Welcome to the 400EX Forum!

The best thing to do is to put the jets you think you will need and ride it a bit then check the color of the electrode on the plug. If its tan/chocolate brown your good, if its black too rich and white is to lean.

You will probably need a 152 to 155 main jet, the 400ex also benefits from a larger pilot jet. You will want a 42 pilot. You can buy all your jets at www.jetsrus.com or at your dealer. Just make sure they are keihin jets and not dynojet junk.

As for your mods I think you will be happy. Only advice I will give is I dislike KN filters b/c they let too much dirt in unless you use a outwears type cover that fits over the filter. I much prefer foam filters such as uni.

Anything else you want to know or ask feel free to do so. Please click on the link in my signature, it contains quite a few threads that will be a huge help to you.

[tbrackman84]

welcome, this forum is full of guys who know what they're talking about! even if I don't :scary:

[05DodgeDakota]

Check out the stickied thread link about jetting. Gonna take alittle trial and error.

The Jet kits off of Jetsrus.com are the only way to go.

I like K&N but DO NOT buy a stock replacement unit. Get a Clamp-on type kit such as the one made by Pro-Design.

As for where to order parts, I sometimes buy direct from the manufacture and other times from either Rockymountainatvmc.com or motosport.com.

[eburns631]

thanks alot for the advice...one more question, would it be ok to do the jetting myself or take it somewhere to be done. I definitely dont want to mess anything up but at the same time im not wanting to spend alot of money on getting it done.

[05DodgeDakota]

yea do it yourself. Just always err on the side of caution, in this case that means being rich on the Air/Fuel ratio