Carb Jetting etc..

[Newbie400ex]

I just bought a QuadWorks atv power kit consisting of a K&N filter,prefilter, and jet kit. I was wondering what the easiest way to remove the carb is. Is it possible to do the rejetting with the carb in place?(since the access plate is on top). I figure it's better to draw on some of you guys' knowledge rather than having to find out the hard way. Like trying to remove the spark arrester screen and breaking two out of three bolts :mad: Is this rejetting going to really make a difference with my stock exhaust? I know the K&N will flow more air but... what comes in must go out. Unfortunately I am trying to get all I can on a budget and any little trick suggestions would be much appreciated. Oh yeah by the way what does "bump" mean? (besides a rounded raised surface on the road :)

Stock 400ex

[Desert400EX]

I doubt that you will notice much if anything by simply rejetting a stock 400EX.

As for the term "bump", it is commonly used as a means to move a post "visually" up the page so that it remains near the top, and in plain view as opposed to letting the post "fall" to the 2nd or 3rd page where fewer people will see it. ;)

[Newbie400ex]

I also plan to drill holes in the airbox lid, and grind the header welds. From racecar experience ANY obstructions or sharp bends will cause turbulence which in turn causes lower velocity and higher backpressure. Also the kit I bought recommends the jet change because of the filter change. I don't know if it's just a way to sell unsuspecting newbies like me a jet kit or what. Also I read another thread saying Honda ships the 400's lean due to emissions. I think I would rather run slightly rich anyway. (thanx for not flaming me about the bump thing :))

[Desert400EX]

Indeed it is better to run a bit rich, rather than a bit lean. It'll help keep you from roasting valves and what-not.

Power wise, your quad will certainly run better when properly tuned.

[redrider ex]

it can be done with the carb on but it is much more easy with it off.

[Newbie400ex]

Ok, I got the kit in and everything seems to work ok. I ground out the header welds. I measured it before and after with dial calipers and grinding it opened up the head pipes .080" (around 3/16"). Funny thing is the Dynojet jet (DJ142) looked smaller than the stock jet (148). The Dynojet tech assured me that it would still flow more fuel due to the different taper. But techs will tell you anything:rolleyes: . I noticed a little midrange improvement but nothing serious. Top end on this thing is PITIFUL. So.. $150 down on billion to go.... I sure hope a good silencer makes more of a difference than this did.

[wilkin250r]

The jet kits are designed with an aftermarket exhaust flow in mind, so I don't think you will see a big performance increase with a jet kit alone. The pipe should wake things up a bit. I haven't personally tried the jet kit, but I've heard good things about them. Of the reviews I read, a 400EX with silencer, filter, and jet kit will pull 4 bike lengths on stock in 100yrds.