Today I replaced the screw thing (jet?) on my 400. I guess stock is 148 and I went to 155. Most of my riding is around 3000-6000 ft. I do occasionaly go as high as 12000+. Also I have a White Bros slip on and K&N Filter. Does that seem about right?? I didn't take the carb apart, just swapped the screw on the bottom. I did notice that when I took the lid off the air box it ran smoother and was a bit faster. I guess my question is: Did I do that right?? Or am I supposed to use the needle thing that came w/ the jet kit?
I ran it all day with that set up and it did real good. Thanks, Drew

 

PADZZ2,
Well, Lets see if I can remember all those questions...first of all, you may have gone a little fat on you main jet. The fact that the bike ran better with the lid off tells you it was too rich for the available air. If it is running well at the top end that way, you can either leave the lid off, or replace it & drop one size on your main jet.
As to the jet needle, test your machine at 1/4 to 3/4 throttle & check for misses or flat spots..if none, then your needle is ok as is.That's one of my pet peeves about jet kits; the contain too many items that are not needed by most riders, like jet needles, pilot jets, etc. People change all the jetting at once, when 90% of the time the only change necessary is the main, & then they are stuck out in left field without a clue.Granted, there are some isolated situations where jet needles require a smaller diameter or different taper, likewise with changing the pilots.Continued prolonged operation at very low rpms and/or drastic elevation variations from sea level, for example. Otherwise, an adjustment of the stock jet needle or pilot will take care of any problem.
Regarding your riding at 12000', the jetting you use at 3000' will certainly be too fat for the thin air at 12000'. It won't cause any damage to the engine, but will cause sluggish performance. For just a day trip you may not wish to lean it out, but just put up with it.
Here's a couple of rules to help you:

high elev.= thinner air= leaner fuel mix
lower elev.- more condensed air= fatter mix

pilot jet--idle to 1/4 throttle
needle jet--1/4 to 3/4 throttle
main jet.. 3/4 to full throttle
If you have jetting problems determine wher in the band they occur, and refer to the above.
This is a long answer to some short questions but hopefully they will clear things up a little fo you.

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THE AZ HARD PACKER, calmiller@kachina.net

save the public land FOR you, not FROM you..join the Blue Ribbon Coalition online @ www.sharetrails.org



[This message has been edited by hot_shoe_cv (edited 01-01-2000).]

 

what kind of jet kit did you get ? K&N? DynoJet?

 

I bought the K&N Powerkit which is basically the K&N filter, outerwear, and Dynojet kit. This, to me anyway, was a big waste of money. The Dynojet kit did little, if anything, to help the performance of my 400. If you are not having any problems with your mid-range, then leave your needle alone. It is a real pain to get at and the changing to the Dynojet needle gave very little if any performance boost. In order to change the setting of your needle or to swap it out for another, you have to take out two screws that hold it in place. These are very small phillips-head screws that almost always strip out. Be sure to use the right size screwdriver and use quite a bit of pressure. For your riding, that 155 main seems very big without any modifications to your airbox. I live in the great Mud-west where we have an elevation of 743 ft above, and I run a 160 main w/K&N filter and 11-1" holes drilled in the lid. Here is something to think about--when the 400's are produced and tested, where do you think they are ran at? It is probably somewhere where the elevation is probably no higher than about 1000 ft above. When you change a main jet, what you are doing is dialing in your quad for your conditions. I have found that when it comes to main jets, that bigger is certainly is not better (unless you have an endless supply of sparkplugs and enjoy sluggish performance). You might actually have to jet down for your elevation. A stock main jet on a '99 400EX is a 140. A stock main on a '00 is 148. You are always safer to start big and work your way down to the one that works the best. With the radical changing of elevation you are riding in, your best bet would be to carry a pocket full of mains, a 17mm wrench for the carb bowl and a 7mm socket (or 8mm, I can't remember) for the jets. Ride On!

 

Thanks. My jet kit is a K&N.
I don't think there was anything in between the stock and the 155. Or I probably would have went w/it. So are you saying that I need to go down??
There is no sluggish performance on my mid. It's actually alot better. I don't know of that's due to the jet or the pipe and filter. So should I just run it with my air box off?? And get an outerwear (which I'm getting anyway)? Or is drilling holes in the lid the better thing to do. I know DG makes a replacement lid that alows more flow. Decisions decisions.
One thing that pisses me off about the jet kit is that it uses a flat head screw. That was a pain in the *** to get to. The stock was easy cuz I could use a socket..By the way my 400EX is a 2000 model.

 

Let's try it again. Are you using an aftermarket exhaust? If yes, is it tunable (disks)? If you are using a screwdriver to change jets, what make of carb are you using or what make is your machine and is the carb stock? Tell me what you have done so far and we can go over this systematically.

 

Feara, sorry, didn't mean to be a pain . White Bros. slip on. K&N filter. Stock Carb...everything else is stock. Oh, 2000 400EX.

 

PADZZ2, I also have a '00 EX. Here is what I have done to mine in Illinos (elev. 743). K&N air filter (recommended), Dynojet carb kit (not recommended), FMF Powercore IV-sa (too loud but good torque pipe), #160 main jet, needle on 3rd groove, 3.5 turns out on air/fuel screw, 11-1" holes drilled in air box lid (not recommended)and stock pilot jet.
You are kinda confusing me when you said you changed the "screw thing" on the carb. To change a main jet here's what you have to do. Be sure you have turned off the gas and drained the carb using the bowl drain screw at the bottom of the carb (there is a small hose near it where the fuel will drain from). Do this first! Next, remove the 17mm bolt/cap from the bottom of the carb. You now can see/feel the main jet from the underside of the carb. It looks like a brass nut that has a small hole drilled in it with a number like #148. You can remove the main with a small socket, either a 7mm or 8mm. Here is what I suggest (remember I am going to try to give you an idea of what you need for your elevation; this is not gospel). For winter and wet conditions, I would run the stock pilot jet (#38), K&N filter, airbox lid w/no holes (to keep the moisture out), air/fuel mixture screw turned 2 1/4 to 2 1/2 times out, a #148 or LEANER main jet (due to the high elevation), and the White Bros. pipe with 8-10 disks. For summer and dry conditions, I would take off the airbox lid, run between a #150 to #155 mainjet, turn your air/fuel screw 3 to 3 1/2 times out, and add 4-6 disks to your pipe. I would get some more advice from other riders in your area though, since I'm from an area where we have too much oxygen (and humidity). Without seeing your spark plugs, it is hard to tell you if you are lean or rich. Being in such a high altitude (little oxygen) you are going to have to run leaner. Ideally you want a 14.7:1 ratio of air:fuel. Hoped I helped!

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a Fast Boy From Illinois (FBI) Riding a 2000 Honda 400EX

 

Feara...yeah thanks. Two more questions though...What would I be looking for on the plug to tell if I'm running too lean??
And where is the air/fuel mixture screw??
I think I will remove some disks as you suggest. Thanks for your expertise.

 

PADZZ2, To tell if a spark plug is running too lean, it will be bone white. It will be almost as clean as new. This is a very bad situation. The old saying, "Lean is Mean", I'm here to tell you that too lean will be very mean to your wallet! Your spark plug should be tan to chocolate brown. This indicates an almost perfect mix. If it is black and sooty, you are too rich or have been running with your choke on. You use to be able to get a free brochure from Champion Spark Plug that gave a pretty detailed explanation (w/pictures) of what to look for when reading spark plugs. Maybe try their website to locate this publication or to find an address. If you have any luck finding this booklet, I would appreciate it if you would let me know. And your other question-where is the air/fuel mixture screw? It is located in a small tube facing downwards between the cylinder and carb bowl. A little tip: If a mixture screw is toward the back of the carb (near the airbox) it is for adding air (turn out to lean out) and if the screw is near the front of the carb (near the manifold and cylinder) it is for adding fuel (turn out to richen the mixture). I believe that the stock setting for the '00 400 EX is 2 1/4 to 2 1/2 turns out. You should get a Honda Service Manual (for about $40) at a nearby shop. If you are technically knowledgable at all, it is pretty easy to follow. Take your time!

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a Fast Boy from Illinois -(FBI)- Riding a 2000 Honda 400EX