Just installed K&N on 400EX +some. questions???

[BornOnFire]

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?

[BornOnFire]

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!

[JOEX]

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]

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.

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]

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]

Kepp in mind...it's a fuel screw, not air. So as you open it....more fuel.

[Texan32]

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]

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]

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