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Noobie question on setting A/F, idle, etc. on 06 TRX400

1996 Views 9 Replies 3 Participants Last post by  retro
I wrote a huge novel then deleted it. I think most of you don't want to read all that, so I'll get straight to the point:

Stock exhaust. New oiled UNI filter, new plug, fresh oil. New throttle stop cable (it was broken when got bike used). Sea level to 2500 feet max riding. Went from stock jet 38/148 to 42/152. Desire better starts cold and less stalling while cold. Runs real well once warmed up fully.

1. The throttle stop piece that threads in to the bottom of the carberator, only barely touches the wheel (that the cable attaches to), in the last 2-3 turns over the knob (before spring is fully compressed). Does this sound right, or should I have a little more slack so I can thread the screw out and have more control? If so, the only idea I have is to loosen the throttle a bit from the other side (by your hand) so the wheel drops down more? It seems that the wheel has a big spring behind it anyhow to cause the throttle to go back to none, right? So if the throttle cable was longer (by loosening at the hand throttle area??) it would drop a little, and lower the idle??

2. When starting the bike with a freshly cleaned carb and larger pilot jet it idles so high. I don't have the #, but it sounds at least 2000 or more. It for sure isn't stalling on me like before, barely putting along. Is the idle simply controlled with the throttle stop cable and the throttle adjust on the right side? Is there any other spot on the bike that this is controlled?

3. The A/F screw. I knew I needed a "D" socket, which I didnt have yet (Motion Pro tool arrives Tuesday UPS says). I tried the .22LR shell method with one side pushed down. total PITA, so I will wait... I watched videos online and read a lot and people give various approaches. What do I do here? Assume it is totally wrong. How about screw it in all the way (without hard bottoming out), then 2 or 2.5 turns out, start the bike and see? If it sounds like its bogging, another 1/4 or 1/2 turn till it sounds good? Then see if another 1/2 turn makes no difference in audio, then back to the original area? Do I do this cold, or let the bike idle up and get really warm? I can't ride it around here (the burbs, no area), but can for sure idle it and even maybe ride it a little in my cul-de-sac 1-2nd gear.

I really am not sure how the A/F adjustment is properly done. I did see about a plug chop, which I am fine doing, but at least want to try to get it in the right area.

4. I see talk about setting RPM. How do you do that? Is there a cheap tool I can use to set it? Maybe an iPhone app that can decipher the noise of the engine and determine RPM? If not, what do you buy to get an RPM reading? Is it simply a tuned ear?

Anything else I should know? This is all in prep for the fall/winter so I can take this out to the desert and know it'll start right now. The wife will probably right it most of the time as I'm on my dirt bike and I want this thing tip-top for her. I cant afford any reason for her to say "I hate riding these things"
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Im gunna answer all your questions in seperate posts. The throttle cable is adjusted wrong from the sounds of it. The way i always adjust mine is loosen the idle adjuster all the way up. And then loosen the cable at the handle bar slowly until it hits the throttle stop. There is one in the carb that it will hit even without the idle adjuster bolt. At that point you know for sure the throttle isnt being held open by the cable adjustment. Dont worry about how loose your throttle is yet. I then start the quad by turning the idle adjuster till it idles high enough to stay idling on its own. Then adjust the cable from there to give 2-3mm of slop at the thumb.
Question number 2 confirms my throttle cable adjusted wrong statement. You should be able adjust the idle down to the point that it dosnt idle. And since you cant that is the cable to tight causing that.
Question 3. The proper way to set your a/f mixture is put it at 2 1/4 turns and start it and get it warmed all the way to operating temp. From there i lower the idle until it just bearly stays idling. You then turn the mixture screw 1/4 turn at a time and give 30 seconds or so between each. Start by turning it in. Go in until it starts to stumble or stalls. If you go all the way in to light seat without it stalling your pilot jet is to big. If it stalls at around 1- or 1 1/2 turns your good. Start it back up if it stalls and start turning the other way. You are looking for the highest smoothest idle you can achive. This is alot of ear tuning and takes alot of practice. If your highest point is more the 3 turns out your pilot jet is to small. You are looking for a final mixture of around 2-2 1/2. Or anything under 3 really. There are rpm guages you can buy but honestly idle is alot about preferance. I keep mine idled just slightly high to help it start easier.
Lastly dont be surprised if the 42 pilot jet is to big for a stock pipe and only an aftermarket filter. In my experiance it is. The 40 pilot jet will more than likely be where you end up. 42 is for a pipe and filter and airbox lid removed.
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