PDA

View Full Version : Just installed K&N on 400EX +some. questions???



BornOnFire
04-12-2002, 09:39 PM
I just installed the K&N filter on my 400EX.

In addition to this, I drilled some openings in my airbox and installed some of those foam "pop-in" plugs to open the lid up a little w/out entirely removing the airbox lid. (I could post pics if needed)

One question..........

After installing these plugs and/or the filter, has anybody ever found it necessary to re-jet the carb to compensate for the extra air inside of the combustion chamber?

After the first "post -installaton" test ride after these installs, I noticed that the fifth gear was "asking" (more like whining) for more fuel.

Is this just me? Or am I missing out on the true benefits of airbox modification by ignoring more important mods?

By the way....what a difference the K&N+airbox mod really does make.

Also.......14 tooth sprocket on order, any advice?

Simple, yet, effective? :confused:

BornOnFire
04-12-2002, 10:04 PM
C'mon, I know I sound like a rookie but give me some love folks. I have only owned this 400EX for two weeks and I need all of the help I can get. I do not want to mess it up the first go around!:D

JOEX
04-12-2002, 10:21 PM
I'd say you should re-jet. Might want to think about an aftermarket exhaust to let that added air flow escape. There needs to be a balance of intake, fuel flow and exhaust to run good.

Also.......14 tooth sprocket on order, any advice?

With stock tires.....Hang on!

Joe

NVR2L8
04-13-2002, 12:18 AM
Yea, you need to rejet since the K&N flows quite a bit more than the stock filter. If you haven't already done so, go up on the pilot jet a few sizes for better cold starting/idling, and leave the clip on the stock 3rd groove. Then buy yourself a collection of main jets and install the largest size--I think a 160 would be fat enough. With too large of a main jet installed the engine should "blubber" at WOT under the rev limiter--go down one size at a time until the "blubber" disappears.

I run a 14-tooth front sprocket most of the time now. With my 416cc engine mods the 14 performs better than the 15 in the sand dunes, and I prefer the close ratio with the 14 for technical or woods/trail riding. The quad will be a little more "torquey" with the 14 due to the lowered gear ratios...the only downside to the 14 is that you quickly run out of gears when riding in open areas.

04-13-2002, 01:30 AM
NVR2L8 offered very good advice and I would add that with just the K&N you may be able to get away with adjusting your air mix screw. You should least do this until you get some new jets to dial it in properly.

If you also have a silencer or pipe you will have to re jet and maybe even a little higher than noted.

BornOnFire
04-13-2002, 10:50 AM
From the info so far, I guess that a re-jet is necessary. I will try the air/fuel mixture screw for starters. How difficult is it to re-jet the carb? Can I do it myself? I am good with mechanics and I love to get dirty but I have never really messed with the 400EX, let alone a four stroke motor. I guess I should buy the service-repair manual. Anyone have one here? If so, how much are they and where to buy? I will need to adjust the valves after two more tanks of gas. I will attempt it myself. Any advice? Thanks for all your help people! Ride on........

James :devil

Stunz
04-13-2002, 11:34 AM
Kepp in mind...it's a fuel screw, not air. So as you open it....more fuel.

Texan32
04-16-2002, 12:09 PM
If you have just the slightest mechanical knowledge, you can do just about everything to your quad. I agree with the others. Jetting is a good idea. In your case (since you haven't bought a new exhaust) i would get the K&N jet kit ( 50 bucks). It gives you about 8 different main jets. It also gives you a new needle. I think the needle is just a little bit different than stock, but not sure on that one. I also recommend running a bigger pilot jet. www.servicehonda.com sells them. 99103-420-0400 is the p# for the 40 pilot and 99103-4200420 is the p# for the 42 pilot. They are like 8 bucks each. If it doesn't get too cold where you live, the 40 should work fine. If you go with a new pilot, you don't need to adjust your mixture screw. Also if you put in the bigger pilot, you can take out your choke plate. Trust me, i live in NorthDakota...I ride in the middle of winter and i don't need my choke any more

A couple other simple things you can do....use a dremel tool and grind the weld inside your header pipe. Just take it off the motor and you will see what i'm talking about. And, you can take the baffle off your stock muffler. If you grind the welds and remove the baffle, you could probably run about a 155 main jet....

These are REALLY cheap and quite effective mods

BornOnFire
04-16-2002, 03:32 PM
So, if I buy the K&N re jet kit, it doesn't it come with the pilot jet? Also in regards to the weld inside of the header, are you saying that it actually restricts the flow of the exhaust? WTF. Honda doesn't do this? And as far as the baffle in the stock pipe. will that mess with the compression? Should I do it before jetting?
Thanks a lot for the info man, I am learning..........

By the way, I am getting the Renthal 14 tooth sprocket today!

We'll see how it works hopefully by tonight!

Laters,

James



:devil

PDunes300ex
04-16-2002, 06:43 PM
If i can change jets, just about anybody can. Just be careful with the small screws on the carb cover cause they are small and soft. I suggest slightly tapping the screwdriver with a hammer while turning so you don't strip the little buggers. Grind out the header pipe weld. Get an aftermarket slip-on...everybody has an opinion on what works best. If you ride in dusty areas get an outerwears for your filter. if you get the dynojet jet kit...it gives pretty good suggestions on what jet to run according to the mods you have and the altitude at which you ride. Sorry so long

Texan32
04-16-2002, 08:22 PM
Here's what i did....i bought a DMC exhaust, K&N, outerware, and jet kit. When i opened the jet kit, i was dumbfounded to find there wasn't a new pilot. I guess thats just how they do it. I followed K&N's instructions on how to change the jets. It really is a cake walk. It also tells you to just adjust the mixture screw (hence no new pilot jet). After doing the jets, it worked ok, but it was still kind of a pain to start. Thats when i decided to go with the new pilot. So, i put in a 42 pilot and adjusted the mixture screw back to the stock location (about 2 1/2 turns out). This made a HUGE difference! Three pumps on the throttle and she fires right up. One thing though, now that summer is coming, i am probably going to go down to a 40 pilot. You don't need quite as much fuel with warmer weather. But again, use stock mixture settings.

As far as the welds, i'm not sure how/why honda over looked this, but i was amazed when i took mine off at how restrictive the pipe really is. Take it off, trust me...you'll see. If you do decide to grid the welds, just take your time. The muffler is a little stubern to get off the header. Also, be patient with the header pipe. It take a little twisting and turning to get it out.

About the baffle, it is perfectly ok to take it off. If you put on the filter and especially if you rejet, it will actually help it. You're giving the motor more fuel and air...you gotta let it escape faster.

To keep it cheap and simple, here's what i would do...
-Remove baffle
-K&N WITH outerware (they're only 10 bucks! and it worth the extra protection!)
-155 main jet, K&N's needle with clip in stock location
-40 pilot jet
-remove choke plate
-grind header welds

If in the future you decide that you do want an aftermarket pipe, you will probably need to jump to a 160 or 165 main....but ONLY with a different pipe.

Its alot to obsorb, but if you need anyhting else, just ask

04-16-2002, 09:34 PM
If you ride in dusty areas get an outerwears for your filter.


I would just get the outerware anyway. It will keep your filter cleaner longer and dryer too.

motoxracer690
04-16-2002, 10:04 PM
Ok, I replaced my main jet, needle, filter pipe etc.. What will increasing the size of my pilot do? Isn't it for low end? I seem to have plenty.. Will it increase more? I really don't want to yank the carb again.:blah

JOEX
04-16-2002, 10:31 PM
The pilot jet is for idle to 1\8 throttle. Mainly for starting. Not really "low end".
Read this for a litle more info:
http://www.exriders.com/jetting/jetting.shtml

Joe

Texan32
04-17-2002, 08:10 AM
The pilot is pretty much for starting. Yes, the charts say its for idle to 1/8 throttle. But seriously, who rides at 1/8 throttle. Goint to the bigger pilot will make worlds of difference when you go to start 'er up.

motoxracer690
04-17-2002, 08:54 AM
That explains it..... My EX sputters and lopes when you first start the thing... Dam, looks like Im yanking the carb again... Thanks for the advice.

On another note, when should you do your first valve and tapet adjustment?

bpimpdaddy21
04-17-2002, 09:10 AM
BornOnFire, where can you get the little pop in foam things for the top of the airbox lid. Any help would be appreciated. Thanks.

Texan32
04-17-2002, 09:58 AM
Since your in AZ, i would try a 40 first. It get (and stays) pretty warm there. I'm wondering if a 42 wouldnt put you a little on the rich side. I would say get both jets. They're really cheap.

BornOnFire
04-17-2002, 01:23 PM
Originally posted by bpimpdaddy21
BornOnFire, where can you get the little pop in foam things for the top of the airbox lid. Any help would be appreciated. Thanks.

I bought them at my local Honda dealer but I also found some here.

http://www.toomey.com/html/intake_system_parts1.htm

Check this url for these plugs. They do not show a close up picture but I can snap a few of mine to show you more details. They look neat is you install then properly and my dealer told me that they won't void the warranty.

Let me know if you want the pics.

Laters...

:devil

BornOnFire
04-17-2002, 03:26 PM
Originally posted by Texan32
Since your in AZ, i would try a 40 first. It get (and stays) pretty warm there. I'm wondering if a 42 wouldnt put you a little on the rich side. I would say get both jets. They're really cheap.

Thanks for the info there TEXAN32 You are right, it gets damn hot here and dry. I will try the 40 and buy a 42 for the dead winter. I also ordered a darn service manual today! Hope it's worth the money! Laters...

:devil

Texan32
04-17-2002, 08:42 PM
not a problem at all. Glad that i could help

Desert Rat
04-19-2002, 05:29 PM
The K&N power kit comes with a jet kit that is made by dyno-jet. It comes with several main jets, some good instuctions related to your elevation, a new (different taper) needle and adapter for the jet orifice. I assume that is the same setup when you buy a K&N filter and outer wear and K&N jet kit seperately. There is no need to change the pilot jet. It should still start and idle fine if it did before you put the new jet and needle in. If you don't increase you jet size with the added air flow you will be runing leaner and "hotter". Not good for the engine. Your should try to open up you exhaust to flow more out with the intack mods. Listed below are some economical permormance mods you can make to you 400ex.

1. install a K&N air filter and prefilter, and trim intake/snorkel flange at the airbox or remove air box lid
2. drill holes in end baffle of exhaust pipe, and remove spark arrestor
3. properly clean and re-jet the carb
4. change the sprockets from 15/38 to 16/36
5. run premium gas, and use some carb cleaner once in a while
6. reverse the front wheels for better handling
7. change oil, oil filter, fuel filter, and spark plug at regular intervals
8. adjust i/e valves, chain, and clutch/throttle/choke/brake cables as recommded
9. water-proof all electrical connections with silicone
10.set tire pressure to 4psi fr / 3psi rear, and soften all preload shock settings
11.charge battery, check water levels, and clean the terminals

two_baaalls
04-19-2002, 07:27 PM
Desert_Rat, where do I check my water level on my 400ex??? J/K...

Nice post.

Desert Rat
05-06-2002, 12:27 PM
Haven't been here in awhile. Should have said the water level (electorlyte) in the battery.

whiteknuckle
05-06-2002, 06:41 PM
BORN ON FIRE! these guys r giving you great info for sure! but if i were you i would wait to mess with jetting that damn thing till you get a slip on exhaust, i mean its stupid to do it twice and im sure youre getting an exhaust and if you wait till youre exhaust youll only have to do it once "hopefully" im just like you only had mine 3 weeks or so and i only have a K&N filter myself i notice no changes whatsoever as far as bad goes but i do notice faster acceleration through all gears an d about 1 or maybe 2 mph more on top end. i am getting the white brothers pro meg exhaust which from what i understand is bout the best slip on for the 400 ex, best power gains anyway. so just wait till ya get the slip on it wont hurt running it like you are with only a k&n and you wont have to do it twice.