got a 07 400ex, doin some first mods on it. getting a k&n air filter, getting another air box lid to do the airbox mod where i will open up the lid and cover it with pantyhose and window screen to act as a prefilter. i also have cut off the spark arrestor from the exhaust tip which has improved performance from airflow as well as making it sound awesome. my question is what jetting should i use with these three upgrades? i know about how carbs work but i do not know much at all about jetting. i have cleaned a carb before, not on the 400ex tho. so when describing the jets please be specific, thanks

 

k&n filters let a lot of dirt by you wont ever see one on mine get a foam filter.i would recommend a EHS airbox lid. gonna trust in pantyhose and house screen on your quad?i recomend a 42 pilot for cold starts what is your elevation?

 

im putting a foam prefilter over the filter as well, and no im not relying on screen and pantyhose, thats used to eliminate air restriction up to the air filter as well as work as a prefilter to protect it from water and bigger dirt. i oil the k&n filter and the prefilter. im in central florida so pretty much water level for the most part, temps anywhere from 30*-90*F.

and i am aware of all the premade lids for the airbox, but id rather not spend $40-100 on a prefilter.

 

any jetting reccomendations guys??

 

remove choke and do a 42 pilot and start with a main 2 sizes above stock

 

ok, thanks, what do you mean by "remove choke"?

also, where would i get the right jets?

thanks for the help!

 

removing the choke gives better throttle response.as far as jetting i have a 07 400ex too i have 170 dyno main 42 pilot EHS air box lid twin air filter hmf slip on 565 above sea level. mine might be a tad bit rich on my main.you can get jets at your dealer or at jetsrus.com your jetting should be close to mine.the 42 pilot lets you eliminate the choke ive had no problems starting mine without it. but my choke is still in my carb.

 

Width#---- Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

 

wow, im excited already lol. so how do i remove the choke, like whats in the process? im sure its simple but i dont have the atv with me, its at other house. and so with no airbox lid, no spark arrestor, and UNI air filter i should run arnd a 170 main and 42 pilot? and i understand the measurements for different brands, but if i have a choice, what jet brands are better?

thanks alot for the help, jst now getn into the jetting and things like that. also, if i get bigger jets to compensate for more performance, does that decrease my fuel efficiency?

 

there all the same but dynojet provides a tool for the fuel mixture screw.bigger jets mean more performance so yea its gonna suck more gas.