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Discussion Starter · #1 · (Edited)
Ok thanks for reading this. I can't get my 400ex to run because the jetting is off. I don't even know where to start. I'll try to give you as much info as I can for now...

Elevation ~700 ft.
It has K&N, no lid, and a white brothers e-series pipe.

Ok the pipe had a plate on the back at the tip covering the hole so no air was getting out. So I took that plate off and can now see down into the pipe.

It will only run with the choke on. I've tried 38 pilot, 40, and 42 with all different A/F screw positions. It seemed like I was getting better results with the 42 pilot with the screw probably 2.5-4 turns out. Almost kept it running for a while. Like I said it runs great with the choke on so doesn't the choke richen it up. So if it'll only run, that means I'm too lean right? So should I go up to a 45 pilot??

Seriously this is soooo aggrevating. I'm wasting money buying all these random jets and nothing is working. I've also got a 165 main in it right now, but have 160, 155, 148, and 142 main jets.

PLEASE HELP!!!! Where can I at least start??

Edit: it did sit for like a year, the guy told me. I tried to clean it out with carb cleaner, but I don't have a compressor for high pressure air, and I really am apprehensive about taking the carb apart and soaking it because there are just so many parts. Any ideas???
 

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I am going to say with the 42 pliot, and the 165 main you should be close on the jetting, if it will only run with the choke on it is not getting enough fuel, so there is some trash in the carb or you need to go up on the main jet maybe a 175, take the bowl off the carb and blow up into the jet passages you might also try some seafoam or marvel mystery oil in the gas. Have you tried putting the air box lid back on to see if it would run? if it runs with the lid on you will need a bigger main jet.
 

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^agree P.S. it isn't as hard as what you would think to tear down the carb just watch how you take it apart.
 

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I agree. It sounds like the carb needs to be cleaned.
 

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Discussion Starter · #5 · (Edited)
Ok guys thanks for the replies. Since the post I've taken the carb apart as far as I'm willing to do. I went and got some compressed air in a can to help a little. I took the little black hose and black plastic 'regulator' (air cut valve assembly is what the diagram says) piece off and cleaned all those lines and in the carb and blew the air through as best as I could. Also when I took out the A/F mixture screw, the little pointed end seemed pretty nasty so I cleaned that up good. Getting ready to put it all back together and see if she runs. As far as the 175, I had had it running with the 165 yet so I don't know 100% if that's enough or not enough but that's good to know that it might be a possibility that I need to go up that high.

I haven't heard of that seafoam or mystery oil. Is that like the carb version of fuel injector cleaner in my car?? Is there a carb cleaner I can mix with the gas that will help clean it out even more?
Thanks again guys, I'll update in about an hour...
 

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Discussion Starter · #6 ·
Ok, just tried running it with the 42 pilot and the mixture screw anywhere from 2-5 turns out. Seemed to get a little better the farther I turned the screw out. Is it unheard of to try a 45 or even higher pilot? That just seems pretty high. It ran great with the choke on and when I ran it with the choke off and gave it gas it had some "popping/crunching" when coming down. It was a huge backfire but it seemed to be backfiring just a little. Do you guys think I should try going up on the pilot and maybe even the main? I don't think I can get any cleaner on the carb, It seemed like the air was flowing pretty good when I was spraying it.

Any ideas? You guys still think its dirty or maybe a little to lean on the jetting?
 

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Try putting the plate back on the exhaust pipe. That is their method of sound control. You are not getting enough back pressure. Was it running good with the plate on?
 

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Discussion Starter · #8 · (Edited)
well it was never running good. i bought it 2 weeks ago knowing it wouldn't stay running, but if you just constantly gave it gas it ran just fine. I just figured a little carb cleaning would do the trick. i'm gonna try to put the plate back on, i've just never seen a pipe with plates over the back restricting the outflow of air. but i'm gonna put it back on and let you guys know. anyone live in indianapolis? LOL


but also if back pressure was an issue, it would be through the whole RPM range?
 

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Like I said it runs great with the choke on so doesn't the choke richen it up. So if it'll only run, that means I'm too lean right?
When you removed that plate, you increased air flow. When you increase air flow you need to add more fuel to compensate. That is what the choke is doing.
 

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Discussion Starter · #10 ·
Is it unheard of to get up to a 45 or even a 47 on the pilot? I guess I was just worried because that's such a big jump from stock. Shoot for all I know he could have it bored and a cam in there lol. He just didn't mention it when I bought it. Anyways maybe I'll buy those jets and see if that helps at all. I'd rather have the increased air flow (and jetted properly) to get the most power I can. Thanks for the reply. If you could just let me know about the 45-47, I'll buy those tomorrow and try them...
 

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My dad had that exhaust on his Warrior. The plate is normal, it's on all of them. It's not restricting just making it not so loud, even though those exhausts are BEAST anyways.
 

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My dad had that exhaust on his Warrior. The plate is normal, it's on all of them. It's not restricting just making it not so loud, even though those exhausts are BEAST anyways.

I had the same issue with my 400ex, when I start the engine I need to do it with a half choke, I need to let them at idle speed for around 3 minutes, then I ride it (with the half choke) for around another 2 minutes, then I go full throttle and begin to be make some lost power, that is the signal to close the choke and run ok!

Looks like works ok when the engine gets a warmer temp.

Note, this is only when the atv was off for around 1 week, if the engine is hot, she turns on in a second!
 

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Discussion Starter · #13 ·
Alright guys, tore apart the carb. I didn't buy the carb cleaner but I bought two bottles of Seafoam and let it sit in that for about 1/2 hour. Cleaned it up best I could, put it all together and still no idle. Runs great holding the throttle, but no idle.

I really want to believe that I'm too lean because of the fact it only runs with the choke on (and man does it run beautifully with the choke on) but I have a nasty dark plug (which is really confusing me), and from reading the Honda forums, and everyone else's jetting specs, I think I'm too rich. I'm gonna try some small jets tomorrow, but do you guys have any other things to check while I'm out there? This is starting to piss me off because the carb is clean as hell.

Would crap in the gas tank maybe be doing this? Like small particles? What about an accelerator pump? Do the 400ex's have one? What is it? Could mine be dirty or broke? I thought I briefly saw that in another thread but got confused.

Thanks for any advice you guys can give me.
 

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Are you saying it runs good except for idle? Have you checked your idle screw to make sure it hasn't backed out?
 

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Discussion Starter · #15 ·
No it won't idle at all. When I put the choke in the first position on, it runs idles great, but when I turn the choke off then engine shuts down. I have tried every single combination of pilot jets 38, 40, and 42, main jets 138, 148, 155, 160, 165, and mixture screw in all positions for the last two weeks and cannot get this POS to run without the choke on. I've pulled the carb, cleaned it, tore it down, dunked it, reassembled to no avail. It putted 4-5 times today without the choke and that's the closest I've gotten to an idle.

I've been reading about taking the choke off to get more airflow and putting the 42 in with 2.5 turns on the mixture. You think this will get me anywhere? I've just been reading a lot online and my head is spinning! When I modded my rappy, I rejeted to what everyone said, hit the start button, and BAM...this honda is getting on my last nerve!!

Edit: sorry for the long rant, I'm just losing my mind!!!! LOL
 

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Discussion Starter · #16 ·
sorry, didn't even answer your question, no idle screw hasn't "backed out" (you mean fell out?). It's in there, seated properly...
 

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sorry, didn't even answer your question, no idle screw hasn't "backed out" (you mean fell out?). It's in there, seated properly...
I didn't mean fell out. I meant it may have turned backwards slightly or may have been turned backwards slightly. If it has been turned backwards, then the throttle plate may be closed all the way and that wouldn't let it idle. Have you tried turning it clockwise a little to see if it will idle?
 

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ok My turn...... IF you remove the black cover from the carb look up towards the top right where I'm pointing make sure that is open with either an even gap or nearly even gap (see below).
Also I noticed you didn't get any carb anc choke cleaner? WHY? you went out and spent almost 20 bucks on seafoam when you needed carb cleaner, your Idle circuit is STOPPED UP or someone has screwed with the slide settings and accellerator pump settings. save yourself a headache put the 40 slow jet in and bump the main up to a 170 if you can alter your jet needle settings drop it one clip. The reason your plug is black with the choke partially on is you have taken away airflow from the carb. You cannot just soak these carbs you need to remove all the jets and float, float needle pilot screw, all o-rings and spray the crap out of it. then blow it out. some of the orfices in these carbs are waayyyyy too small to just soak them.

 

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Agree^^^^^^^^!!!!
 

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Discussion Starter · #20 ·
TRX thanks so much for the tips. The seafoam was only $10 and a can of carb cleaner was $25. Anyways that point is moot. I'm not sure of the gap you are speaking of unless you mean where that arrow is. Mine is perfectly straight. Here's a pic:



Ok I may be a complete and utter retard (no offense to anyone out there)...
Which of these is the choke OFF? I may have possibly had the choke ON the whole time. UGH I'm gonna submit this reply then go out there and eff around for a minute. Man if it ends up that I had the choke ON the whole time, I'm just gonna go play in traffic...


 
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