Ballpark guesses for jetting

[oliver1650]

I'm ordering some jets for the mods I plan on doing to my 400ex. I'd like to get in the general ball park so I have minimal downtime once I put everything on. I am planning on grinding the header welds, adding a 06-07 450r muffler, and doing an outerwear airbox lid. I'm also adding a stage 1 hotcam and a sparks key, but those should affect jetting.

Stock is 148 main and 38 pilot right? So I'm thinking in the neighborhood of a 160-165 main and I'm also going to get a 42 pilot, does this sound about right?

[CarGuy7a]

The mods you plan on doing I wouldn't mess with a stock muffler. Get a good slip on like an HMF or something. Those stock mufflers are heavy and restrictive and you won't see the full gain of your cam and other mods.

I would start with a 40 pilot. I tried a 42 with the mods I have in my sig and for me it was so rich it wouldn't even start even with the a/f mixture screw at 1/2 turn out. I am running a 160 main jet.

I did just put in my Sparks +6 key in last night but haven't had time to try it out yet. It was raining last night after I got done with it.

[redrocker]

Sounds like you know what your doing :)

[oliver1650]

I'm trying the 450r muffler since I want to keep the quad quiet. I remember several people saying the the 06 and up 450r stock system was straight through and flowed really well. I also don't want to spend a huge amount of money on something like a FMF Q4.

[CarGuy7a]

There is another alternative pipe I just thought of. The Lexx. It runs $199 at rockymountainatvmc.com. They have a ton of tuning options. You might be able to find a steal for one on ebay.

The Lexx comes with a quiet core installed that runs about 96db. They also have a trail saver quiet core that busts the sound down in the mid 80's db range.

Definitely look into it. If I ever need another pipe I'll either get this one or an HMF, noise really isn't an issue around my area but I am still considerate of my neighbors.

Here's the link for the Pipe at rockymountain. Watch the videos for it and it shows all the different tuning options.

http://www.rockymountainatvmc.com/productDetail.do?&navType=type&webTypeId=57&navTitle=Exhaust&webCatId=18&prodFamilyId=19536

[oliver1650]

Yeah, I thought of that too, but I'm really cheap. If I bought that particular piece, I would be pretty much doubling the amount of money I'm spending on these mods. I appreciate the suggestion though

[honda400ex2003]

160 main, 40 pilot, 3rd needle position(stock) 2.5 turns out on the f/a screw. i have heard a few things about the 450r exhaust that were pretty good. let us know how you like it! steve