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first mods on a 2007 400ex
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Posted by: kilgoja

ok i just got back into riding atv's after some years off.....i recently got a 2007 400ex since i mostly ride trails and such....i've been looking around a lot and have decided on a motoworks slip-on pipe.....they say to use a 170 main jet if i take the air box lid off....i was thinking of getting one of those pro-tec air box lids that let air in and keep dirt out...they also say to put the clip on the 3rd slot and turn the mixture needle out 3.5 turns....how many turns out is the stock setting?...just curious...haven't gotten into it yet to find out......what brand of jet do u guys use?...just wondering...also i plan on using a moose racing air filter....any info on any of this would be appreciated

Posted by: dang400ex

Hey there...I havent heard anything about a Motoworks pipe so I'm not gonna say anything about it. I would stick with the Keihen jets(same brand as stock) so that the numbers dont et all jumbled up when you try and use another brand. I would also get a 40 or 42 pilot jet to help with starting. I would use a UNI filter...many ppl say that they are the best.

Posted by: kilgoja

well the motoworks pipe is fairly new but it was rated the best by atv rider mag... www.motoworks.com ..there is a deal on ebay where u buy the slip on and they throw in a dynojet kit and a uni filter...all for $299....i was thinkin of the moose filter cuz it comes pre- oiled with the perfect amount of oil...i really haven't had any problems starting the engine...i just have to blip the throttle for a few secs at first....i did turn the idle speed up a tad to help with starting....maybe 1/16th of a turn...may be different when it gets cold outside....thanks for the advice...

anyone else feel free to chime in

Posted by: speedyquad

stay away from the dynojet kits, read the faq section here: www.jetsrus.com
and honestly, suspension should be the1st mod,

Posted by: stvemerz

Another cheap and easy mod is the Curtis Sparks Adv. key....$20.00 plus and easy to change...Just need to get a new side cover gasket. I like the throttle response it gives by advancing the timing 6 degrees...

Posted by: mitchamus

Who cares if the filter come preoiled one ride and you'll need to clean it.
Hmf sport slip 239.00 with foam air filter and jets add 58.00 will be the same price. around 300. thats ordering direct thru HMF.

Posted by: kilgoja

ok...interesting.....thanks for the replies...but i don't think it's necessary to clean ur filter after every ride...lol.....anyways i have another question......they say that with different temp and altitude u have to change the jetting...just curious as to why...because with the stock jetting u don't have to change anything...u can ride fine no matter what the temp or altitude ...right?....i'm kinda new at this jetting and piping stuff...if someone could shed some light on this subject i would appreciate it....also does jetting and piping affect the reliability of the engine much?...thanks for any help

Posted by: AbnMP13

Jetting info here