Airlid Removal Only Mod

[meyaya]

Will removing the airbox lid produce any gains in performance? This is a bone stock 2002 KDX200. I will eventually get the pipe and silencer but was wondering if there is any noticeable gain when only the lid is removed.

Thanks, Jeff

 

[domino dave]

Do KDX's have airlids?? All these years, I have never seen one. Dave

 

[NCFRC]

Bone stock , which includes jetting , yes it will help the bike breath better and be slightly more responsive.

Cut the rear 2/3rd's off the lid , leaving the front mounting point for
the CDI unit intact , that will give you all the air you need plus give you a little water protection on the front of the box.

Have fun :cool:

 

[bazmaster03]

i just pulled off my whole lid and bolted the cdi on the side of the plastic close to the airbox and i put a screen over the airbox so the big stuff wont go in and it seems to work good ....and for worrying about water going im not too afraid cuz it is still at the same height so if it goes in with no lid it would have probably went in with a modified lid anyways ....just my 2 cents

 

[mudpack]

Will removing the airbox lid produce any gains in performance?

Only if the bike is jetted too rich with the lid. (logic speaking)

Tell you what, I'll take the lid off my stock 200 next time I ride it and let you know what my opinion is.


Or, you could do the same.......??


BTW: putting panty hose or window screen or wire mesh over the top might keep out the big stuff, but the air filter will do that, so what's the point?

 

[julien_d]

BTW: putting panty hose or window screen or wire mesh over the top might keep out the big stuff, but the air filter will do that, so what's the point?

To help the air filter stay cleaner for longer?

 

[mudpack]

No, not really.

 

[23jayhawk]

I know it is part of KDX lore that removing the air box lid is the ticket to unlocking free horsepower, but I'd like someone to demonstrate that based on either dyno numbers or sound logic.

Measure the dimensions of the stock inlet slot on the air box lid and calculate the cross sectional area. Then compare that to the area of the inlet venturi of the stock carburetor.

And then factor in that the air box is effectively a large accumulator at atmospheric pressure.

How does opening up the inlet area improve airflow through the carburetor?

 

[mudpack]

Ken, you're liable to get a bunch of up-in-arms responses to that one...but I believe you are right.
We'd all like to think that we are smarter than the factory's engineers, and can second-guess our way to power that Kawasaki has knowlingly left on the table. Fact is, the factory boys are pretty educated and experienced, have all kinds of hardware and software to develop the best systems within their parameters, and the time and budget to come up with an intake system that is (relatively speaking, of course) quiet, water-ingestion-resistant, and still produces max power.
For us to think that we can come up with something better by simply drilling a few holes, cutting something in half, or leaving something off is giving ourselves far too much credit and giving the factory not nearly enough.

That said, the engineers do have to work "within their parameters". If they have a goal of XXdb as the maximum, and they have to reduce the airbox's intake opening to achieve that decible goal, will they do it? How much are they willing to sacrifice one goal to meet another? We just don't know. I'm betting the power sacrifice (if there is one) will be so small as to be unnoticeable to the average rider (yeah, I know, we are ALL above-average riders!!).

Bottom line: if I'd thought removing/modifying my airbox would give me even two extra horsepower, I'd have done it a long time ago. :cool:

 

[glad2ride]

I don't see a lot of people that pull them off commenting on how thoroughly they had tested their jetting to get it perfect BEFORE they take off the lid or mangle it. I think at least SOME of the "it's now more powerful" crowd benefit from the jetting actually being closer to correct afterwards.

... and it will sound louder, and noise = power, right? (NOT REALLY, as I was just kidding)

 

[meyaya]

Thanks for all the input. I took the lid off and remounted the CDI unit or whatever it is next to the wired heatsink thingy. There is a threaded nut on the frame crossbar at the rear of the airbox. I will test ride it in 2 weeks and will adjust the needle, air screw and main jet as many times as it takes to get it just right.

We shall see if there is a power difference and yes I know more noise does not mean more power. I wish I could hook it up to a dyno stock and modified to see the real difference.

 

[james.keaton]

Not picking a fight, just wondering...If the factory did such a great job on the air box, then why do 220 riders switch to the 200 carbs. Why did kawi even produce a KDX with inverted forks for one year and then change back the following year? And last but not least..."How exactly does the posi-trac rear end on a Plymouth work? It just does!". My point being is that the factory doesn't always get it right, so I believe that is some cases there seems to be improvements over factory. They made the snorkle lid to make sure that water wasn't going to get in the intake, but my KDX has had the lid removed since '91 and there has never been a problem with water. It seems that if there is less restriction on the intake then more air will make it into the engine. Also, everything I have ever read is that the stock jetting on the 200s were a little rich, and many have found the sweet spot on jetting. Even better than what factory has done. Anyways, IMHO there is always room for improvement.

PS - I hope you got my Joe Dirt qoute, and didn't think I was serious. ha ha

 

[_JOE_]

The factory jets the bikes rich to provide a margin of safety against conditions, oil quality and rider. It's common knowledge that ANY bike in it's stock condition can be made to work better for a particular rider by rejetting.

Chances are good that the stock airbox lid might cause a very slight restriction at wide open throttle under a heavy load. If you remove the restriction it will allow a little more air into the box and effectively lean out the jetting slightly.

That being said, you could definately get a much more impressive gain in power and response by simply jetting the stock setup. Or you could remove the lid and jet it for that setup. Either way the jetting is the key to added performance.

 

[ranger306ci]

I have removed snorkles ,and opened up the airbox on all my kawi's in the past. but I always jet accordingly. Usually it only takes a small change in the main jet.
Now, about being jetted rich at the factory. That is no longer true!
My newer bikes I have bought were actually lean from the factory. They lean them out, so they run hotter for better emissions. So, if doing this on a newer bike, you MUST rejet!

 

[mudpack]

why do 220 riders switch to the 200 carbs.

Why did kawi even produce a KDX with inverted forks for one year and then change back the following year?

And last but not least..."How exactly does the posi-trac rear end on a Plymouth work?

I could tell you, but then I'd have to kill you. ;)

Mud

 

[ranger306ci]

you know the answers to all three questions? May I pilgrimage to your domecile, and lay postrate at your feet?

 

[NCFRC]

[

We shall see if there is a power difference and yes I know more noise does not mean more power. I wish I could hook it up to a dyno stock and modified to see the real difference.[/QUOTE]


The best dyno is really your butt , you can look at all the dyno graphs and they still won't give you a good picture of how its going to perform on the trail or track.
Bottom line ,,, the more fuel and air you can fill that cylinder with , the more power your going to have.
Is removing this lid going to give you five more HP ,, no-way !
But all the small things will ad up to a difference you can feel.

 

[G. Gearloose]

In my and many other's experience its impossible to leave the lid alone and jet it correctly.
The end result is a better running bike. Yes more power if you know what you are doing.

Aside from being moderately restrictive, the snorkle and lid cause the jetting to go unnecessarily rich the more air drawn (read high rpm large throttle opening)
The difference can make you jet off by 2-3 jet sizes when doing a plug chop. The result is the main is never perfect at WOT both high and lower rpm, either too lean or too rich depending.

Open the airbox, case closed, problem solved, jetting is not longer rpm-variant.

 

[domino dave]

I have been following this thread with interest. I am still waiting to hear from the guy who said removing the airlid was a huge mistake ... Jeff, I am thrilled to hear you got your lid off, and are going to play with your jetting ... A man after my own heart! I spend as much time in the garage with my bike as I do on the trail. To me it is half the enjoyment.I think NCFRC is 110% correct. "The best dyno is really your butt". I went through all that dyno stuff, just to have to re-do everything to make it run right, for me ... You will know. Start with your lid and jetting and go from there . Have some fun!! Domino

 

[NCFRC]

If I had to just ride and couldn't experiment with things in the garage I probably wouldn't be into this sport. I started turning wrenchs as a kid 35+ years ago and still today enjoy finding things that work. I've cut many a pipe apart and lost a ton of power also.
Oh well , you have to learn somehow.
Too many kids today can win at video games but don't have a clue how to change a spark plug ,,,, hmmm , probably smarter than me.

 

[meyaya]

First Test Rides

I just got back from the weekend camp/riding trip. A little more info on my 2002 KDX200. It is my wife's bike that I bought last year with about 90 miles on it. Stock tires, chain etc. The bike is ridden about 50% on logging roads so when I ride it is ridden pretty hard on those roads. The rest of the time is on trails but usually 2nd and 3rd gear stuff. My wife does not ride it hard. The only modification is the airlid removal. The oil is Bel-Ray H1R at 40:1 with fresh 92 octane pump gas. I have been riding and desert/woods racing KX250s for 20 years.

The report: More topend power but cannot clean up the low revs. If I wick the throttle 75-100% there will be a slight bog followed by increased revving. I switched the needle clip position from position 2, 3 and 4 but could not get clean throttle response. I also tried various main jets and air screw adjustment. Making the bike richer with the air screw and needle clip made the bog almost go away but then the bike was blubbery and not responsive. I saw a response from someone that said they had the same off-idle bog problem and also tried jetting but had no success. Could this be a needle taper issue or needle jet issue?

I have read most people are using 155 main jets but have done plug chops that show the bottom of the insulator still white even with a 162. I ride a lot of gravel roads so I want to error on the rich side for the high revs. I think most riders have their bikes jetted for woods and not for 5 minutes of charging hard up a logging road.

I am thinking of putting the airlid back on since it is just for the wife. She even complained about the low end throttle response.

In the future would a FMF pipe, silencer and airlid removal cure my throttle response problem?

Jeff

 

[mudpack]

Will removing the airbox lid produce any gains in performance? ...wondering if there is any noticeable gain when only the lid is removed. Thanks, Jeff

Your last post was a fairly comprehensive answer to the questions in the OP; looks like I won't bother trying to get a performance gain by removing my airbox lid.
It does indicate (to me, at least) that the lid plays a significant part in the overall tuning of the engine.

would a FMF pipe, silencer and airlid removal cure my throttle response problem?

No, but putting the lid back on would. :cool:


Mud

 

[NCFRC]

In the future would a FMF pipe, silencer and airlid removal cure my throttle response problem?



The airlid isn't causing the bog ,,, I'm sure the additional air noise is what most non-aggressive riders hear and doesn't sound normal.
Put an FMF torque/woods pipe with the stock silencer on it , get it jetted
correctly and you'll have a good running bike.

Buy some 607 reeds while your at it.

Just my opinion :cool:

 

[james.keaton]

I just picked up my set of 607 reeds today? I will get them installed tomorrow. From what I can tell it is straight forward, and very easy to do. How big of a difference do these make?

 

[meyaya]

From what I have found in the kdx forums is that there is a definite bog caused by the complete airlid removal especially at sea level where it will run the leanest. Bikes seem to run lean here in Western Washington. The bog is when you are going at very low rpms and then wick the throttle pretty hard. My 1993 KX 250 never does that. I have read that a sharper tapered needle Like a DEK or CEK will make it much better but the bog will not go away until the airlid is reinstalled. Maybe I am too picky but I want the thing to run as close to fuel injected as possible. I think I will put the lid back on and call it good enough for the wife.