I know we've had some heated discusions about the filter in here. I've got the filter and a outerwear. I had been experiencing some dust in the intake tube, past the filter. Last weekend i totally tore the airbox out and reassembled it with some silicone. I reoiled the filter, put it all back in and went riding. I went riding on sunday in alot of dust. I rode last in the pack to see if i could get any dust in the airbox and past the filter. After 45 miles of riding on the Timberline and Marienville atv trails, I had NO dust in the intake. If anyone has ridden these trails they know the dust that you will encounter too. I had a small amount of dust in the airbox though. So my theory on the dirt getting past a K & N filter is, first seal your intake tract, then start worrying about your filter. I'm convinced that there is nothing wrong with running a K&N filter. I do have my airbox lid still intact also. That is prob. helping me out too though.

 

There was some issue with the intake tube not sealed properly to the airbox...

 

Point of note, you said you are also running an outerwears.

I didn't have any dust last time I checked mine either, but I have had dust in the past. I guess it depends on the conditions. I have never had a stock filter pass dust.

I am not willing to take that chance anymore. Over the weekend I put the stock filter back on (and a modified airbox lid) vs the K&N with no outerwears & no airbox lid, ran several timed acceleration runs through all 5 gears. The results: The stock filter was consistantly faster, in most cases by more than a tenth. Not much difference, but a definite argument against the K&N's use. The kicker - no jetting change required, I am still running great on a 165 main with no other modifications to the bike. This data says alot.

 

LOL! Do you think that maybe you were running just a little bit lean with the K&N if you were faster with the stock filter, using the same main jet? Do you have a dyno? I think not. Get your jetting right with both filters, then tell the results.

 

I'd say a 165 main should be plenty fat for any 400EX.

 

Gabe,

Should i rejet? When i pulled the plug it was kinda carboned up. But that is too rich. I don't understand that one. Unless i'm getting less air with the K&N. It would cut out on me every once and awhile at slow speed. Isn't there a slow speed jet too? I wonder if I'm getting too much fuel below half throttle now. I don't really run it at full throttle too much. I'm usually running it in the mid of the power. Doesn't the needle control from a quarter to three quarter throttle? I'm def. not a carb. guy. Do you think if i raised my slow speed jet up and maybe raised the needle a notch i'd help? It had a K&N when i bought it. So i can't try the stock one. I don't even know if i have stock jetting anymore.

 

During time trials, the 165 main turned the best times (I run a 42 pilot as well)... Keep in mind these are Keihin jets, not a Dyno Jet kit. I generally ride at about 700~1300ft above sea level. This bike has outrun piped bikes (and you never know what else) at the races, in the flat out straights, the jetting seems to be spot on.

On the stock EX exhaust, if you are too rich, it will have a very bad spot in the low mid, just before the power comes on (you'll know it when it occurs). After changing back to the stock filter I checked for this flat spot, it didn't happen. The times were even faster than with the K&N and open air box. My air box now has a trapezoid shaped cut out with mesh and foam to help filter the air traveling through the cutout.

 

Per my post above, it sounds like you may be jetted a bit fat. Probably worth a check to see where it's at. The main is really easy to pull out (from the access plug in the bottom of the bowl), the needle isn't too hard to check, the pilot requires bowl removal if I remember correctly

When my bike was stock, the plug would have some black carbon and a white tip. Keeping in mind what we know about the stock 400EX - They tend to burn oil if you don't run a heavy enough weight, and they are typically jetted lean from the box, this seems to figure, the black from the small amounts of oil that were being burnt (before I switched oils) and whitish grey on the tip from the lean jetting.

Stock setup on the 400EX is a 38 pilot, a 148 main, and the 3rd position on the needle.

As I have said in previous posts, I am running a 42 pilot, a 165 main and the stock 3rd pos on the needle. The only (engine) modification to this bike is the air box lid. It doesn't have any flat spots and overall feels pretty good. I haven't done a plug read because it hasn't shown any signs of being wrong, the plug's hard to get to, and it turned the fastest times with this setup.

I have a friend that runs a K&N (no outerwears) on a '99 EX with a completely closed air box lid, his bike ran rich when we played with the jetting, we put it back stock & it runs fine now.

What all this suggests to me is that on the intake side, you don't really need to mess much with the jetting for changing the filter itself (beyond correcting for the stock EPA friendly jetting), but you do, however, if making air box mods.

 

No, I don't have a dyno, but I do have a stopwatch. The bike was originally jetted for the K&N with no airbox lid. The 165 consistantly produced the quickest ETs with that setup.

Went back to the stock filter and a modified lid, same jetting - the bike is faster.

I guess it falls under the same principle of a properly tuned exhaust working better than open pipes.

I know you don't like my views on the 400EX & you have taken quick offense to me offering counter points to some of your posts in the past, but I am going to pass on your attempt to illicit a negative response from me. I think you'll also find that most have found a 165 main is plenty fat for even fairly modified, piped bikes.

 

Gabe:

My plug looks good on the electrode. The white thing, and the tip are fine also. However all around this there is black buildup... I use 10x40 honda GN4 and i ahev a pingry 3 quart oil tank. Could by oil be burning???

If so what type of oil do you suggest?? It is about 0-50 here in the winter (F), and 40-100 here in the summer (F)... what type of oils should i be using???

My bike also runs hot, but it was broken in properly.


later...