new guy

[kcliff]

I found a deal on a 2007 400ex and could not pass it up. I have a couple of questions and would like some on input on what to get and where from. First the engine doesnt idle all that great and I kill it alot in reverse. I believe I have to adjust the throttle. I have to choke it to start it and push the throttle a bit for it to run in neutral. air box is on with filter and it runs great when I get on it. I might not be letting it warm up proper. I am under the impression you start it and let it sit 2min and then run around on it. I bought it from a dealer who bought it as a repo (title says bought aug06) and he bought it for his son but his wife made him get rid of it so I got it for $4200 and the only thing wrong is the rear grab bar is scrapped but not bent and a smudge on the plastic. anyway everything is legit (seems to be and he took a check) I am gonna get a helmet, clymer manual and some nerf bars after the new year. later i want to get an exhaust i thought yoshimira (spelling) but everyone seems to like HMF so I will go that route. should i get a KN air filter and box? what about rejetting the guy i bought the quad from does motor cross and he says dont worry about jetting. any other mods? I wil use it mostly to trail ride and ride with friends. thanks for any helpful input.

Your idling is low so you just need to adj that and that would help it run. If it dies alot in reverse that can be from the idling set to low or the clutch lever might be adjusted to loose. The clutch lever should have a little play in it. If its adjusted perfect you should be able to just fit a penny inbetween it.
As for pipes hmf is a good pipe and its one of the cheapest pipes out but get which one you like cause one pipe from a nother is not going to make a notacable differance just have a differant look and db leval.
K&n filters are the highest flowing filters out which is good. Some people say they let dirt in but i never got dirt in my intake yet. I run teh filter and a outer wear on it. You have to use k&n filter oil on it if you use that filter.

If you add a pipe you have to rejet. You will need a bigger main jet. If you remove the air box lid you will need to adjust the needle. If you are going to run with a pipe and no air box lid or a k&n lid keep the intake stock and get the main jet set right then remove the air box lid and adjust the needle to wear it needs to be. Its easier to adj the carb that way.

[vett_09]

Like LTD said, if you pipe it, you need to jet it. I've never ran a K&N air filter, but I know a lot of people do. I've always ran a UNI filter and never had any problems. HMF makes a good exhaust, and I think they sound good. Yoshi also makes a good pipe, but you'll be paying more for it.

Again like LTD said, you probably need to adjust your mixture screw. Jetting will also help it idle better. You need to jet based on your elevation, but tweaking is always necessary.

[northwest Texas]

Congrats on the deal.

I prefer the UNI's (or other foam filters) because of the simplicity over the K&N. I have 2 foams I can swap back and forth easily, have one clean while riding with the other. The K&N's take so long to clean and dry out, I don't have that much patience.

Best thing you can do is buy the manual first before you go making adjustments and go from there.

Personally, I'd give it more than 2 minutes to warm up but you'll alright so long as you don't rev it hard immediately.

Pipes are all pretty much good. I'd say most guys have only ran one and can compare it to stock and swear by them but haven't compared to other brands.

Please, whatever you do, don't EVER ride without a helmet. It's just not smart. Full protective clothing is there for a reason.

[kcliff]

ok thanks for the replies. I have tried choking it and reving it at low rpms to warm up and it seems to work.

[JDMThoughts]

I had the same thing happen with mine, I live in Jersey and just got mine a couple days back a 2000. I had issues with it trying to keep it running, but I choke it and hold the throttle down slightly so it won't stall out, after a few minutes I push the choke down a little and if it will idle then I know the motor is warm enough to ride.

[hornetgod13]

I had idle issues too when I bought mine. I had to bump up the idle and it took care of it.
I have a UNI filter installed with a HMF slip on exhaust. I rejetted the carb too.
I attached a photo of my HMF with black vector end cap.
Here's a link to some sound clips of different HMF exhausts:
http://www.exriders.com/vbb/showthread.php?s=&threadid=271456