Newbie! need some help...

[Z400central]

Ok so ill be getting a 400ex for my first quad really soon, but i have some issues with the whole jetting thing. i read the article but didnt really get it...Ive been into gas R/C cars and there nowhere near the same tunning wise! so basically if you change anything engine wise, pipe, etc..it makes the engine run lean right? and u dont want this so you have to make the engine run rich again so you buy a larger main jet to let me gas in causing it to run rich..correct? but what do they mean that you can screw it in and out to change the mixture, why cant you just do that? does it not screw in enough or out to make the mixture rich enough? and how can you tell if your engine is running rich or lean? thank you! im slowly getting this! :D

["BLAHH"300!!]

....lets' say you take off your air box lid....more air goes in the carb..so you need to let more exhaust out....bigger pipe'....then you need more gas in the carb to mix with the air....re-jett...you buy bigger jets' they have larger holes that the gas passs through..some gas....can do it in rever's.....
want quieter bike....smaller/more restrictive pipe...less exhaust/more restrictive exhaust.....less getting out as fast wait.....i'd better stop right here......

[SGA]

Welcome to the site! If you add a exhaust and open/mod the air box you need to change the main jet. Thats inside the carb. More air needs more gas. The screw your talking about is the idle mixture screw on the side of the carb. That controls the amount of gas at idle to 1/4 throttle. It usally only needs to be turned out about 1/2 to 1 turn more from where it is if you add breathing mods. Use search in the powertrain forum. You'll learn more than you want to know about jetting. Good luck!

[400exdad]

You will find all the info you need here at this site. Everyone is very helpful here. I just want to let you know that the screw on the side of the carb (big silver one) is the idle screw. The air screw is actually under the carb in front of the float bowl. Mine was totally stock and I found that opening the screw really helped the cold nature of the 400EX. No flames intended, just didn't want him confused...:D

I worked on cars alot before getting into quads. Jetting was never so critical for them. One little change can make big difference in jetting on quads. I have even read where some folks close the front tabs on the air box before putting the lid on so it will leave a crack that makes theirs run the best......

[Chef]

So let me get this straight 400exdad, a little crack in the airbox makes the bike run better...? (I hope you get it, and not think im being a smart*****...lol) :huh ;)

[Kadafiy]

It's kind of confusing at first but it gets easier. Most of the time you can get away with just chaging your main jet which you don't even need to remove the carb for. Just remember that being to lean will not only make yor bike run bad it can cause your bike to seize.

[400exdad]

Chef, I'm serious, the dude actually felt the quad ran better with the tabs between the box and the lid. It most likely distorted the he!! out of both! Go figure. It was probably in a post here.... no wait, I think it was at ATVConnection. I was just trying to point out that there is all kind of information here, some good and some not so........... Just kidding. I have got so much good info here from jetting, to exhaust work, to relieveing arm pump. :D Its all good!

[SGA]

Well of course it ran better. No joke. The small gap allowed more air in. Sort of like modding the air box lid. Maybe not the best way to do it, but it worked.

[Chef]

you guys didnt quite get the joke...if you put CRACK in the airbox it runs better? I know it will run better with more air, but you guys seemed to have missed the joke...;)

[JOEX]

I got it;)

Quads on crack!

[SGA]

LOL, Whats that noise!? Must have been a 747 flying over my head:D

[400exdad]

I get it now.... Sorry, I'm a little thick! :p