Just one more airbox lid question

svmtbman · Mar 14, 2003

Before you all start giving me hell I looked way back in the archives and only found this question asked once without a direct answer.

Ok, here it goes. I just got a '03 KDX200 and was wondering if you can remove the airbox cover and keep the stock pipe on with no jetting changes. (Will this make the bike run too lean, I did a plug reading after break-in and it seemed to be about right but I have read where the bike was setup from the factory a little rich) If so, is their any power gain that you can notice while still using the stock pipe and jetting?

jaguar · Mar 14, 2003

Yes you'll feel a power gain.
Yes it will change your gas/air ratio.
With any engine change you should play with your jetting to see what needs are in order.

canyncarvr · Mar 14, 2003

You found no direct answer most likely due to the fact that there isn't one.

Yes..rule of thumb is the kdx is quite rich out-of-the-box. To assume that and make subsequent less rich modifications without verification of effect isn't a good idea.

Dealers have been known to change stock jetting in an attempt to anticipate problems from customers complaining, 'My bike fouls plugs all the time.' Specifically I know of such a dealer..cuz it happened to me.

In such a case, leaning the bike via modification could lead to severe engine damage.

Beside which even in an oem configuration there is such a huge difference in environment and riding style that a 'one-size-fits-all' jet sequence just isn't going to happen.

Not to impugn, but in most cases reading, 'I did a plug check...' begs the question, 'Exactly what does that mean?' If that 'check' did not include a WOT plug chop and a subsequent proper plug read (having nothing to do with color btw), it wasn't of much value.

Towit:

With any engine change you should play with your jetting to see what needs are in order.

......I read that somewhere........

Otherwise, what jaguar said. ;)

svmtbman · Mar 14, 2003

Ok, I should have known there wasn't an easy answer. It looks like my best bet is to just keep the top on the airbox until I decide to get a pipe and reeds, that way I only have to go through the jetting proceess 1 time rather than two.
Thanks for the feedback, I've done alot of rejetting on streetbikes but this 2-stroke engine seems to be a "little" different.

canyncarvr · Mar 14, 2003

There is'easy' then there is 'direct'.

A direct answer to your question could be, 'Yes.' And likely that would be correct. Maybe not (due to the 'depends' listed above).

The easy answer is to take off your lid and then run some jetting checks..like a WOT plug chop for proper A/F mixture.

Considering the gains that you have to realize even with the stock pipe and S/A with proper jetting and improved airflow, don't hesitate to tweak it! You'll be happy with the result.

kdxsam · Mar 14, 2003

When I first got my '01 KDX200 I ran it stock with the airbox lid off, it didn't hurt anything. It gave it a little more power with the result of a really cool engine noise (because of all the air being sucked through). Then, I bought a pipe/silencer combo, reeds, air filter, and changed the jetting.

svmtbman · Mar 14, 2003

Ok, I'll take it off and check the WOT plug reading and make sure everything looks ok. Thanks for the feedback!

JCW · Mar 15, 2003

I left the air box on my 03, but cut several 1/2" holes in the top of it to increase the air flow. On my bike, the jetting was good when I picked it up (that was the first time I've seen a new one that wasn't too rich??). The air holes did not cause me to change my jetting, but it did double the size of the air intake without messing with the module mounted on the top of the cover. However, Jaguar and Canyncarvr are right in that you should always check anytime you make a change. I can't believe how small the air intake was!

TVRider · Mar 15, 2003

There is a cross bracket at the back/top of the air box with a threaded hole in it. I just took that module and the screw holding it to the airbox lid (which matches those threads) and turned it over and mounted it to that hole from the bottom. I worked like a charm. No Problemo! (My buddy told me about it, I'm not that smart)

paul6585 · Mar 16, 2003

Canyncrver wrote: "If that 'check' did not include a WOT plug chop and a subsequent proper plug read (having nothing to do with color btw), it wasn't of much value."
What isa WOT plug chop. (WOT, I assume is wide open throttle.) I just bought a pipe for my '99 200 which already has the airbox lid cut out. Before installing the pipe and subsequently re-jetting (which I have never done before, I need to rectify a low rpm bog.) Maybe I am in too high of a gear when it bogs because when I am on the pipe she rips.

farmerj · Mar 16, 2003

Paul6585,

While "WOT plug chop" is only tangentially related to this thread, here's some fun reading for you! Go to this thread
http://dirtrider.net/forums3/showthread.php?threadid=62692

and then find canyncarvr's post (about the 12th one down). Click on the link to a discussion w/pictures by R. Rohrich. Also check out the first entry on this forum which directs you to the JustKDX website. There is carb/jetting discussion there that tells how to do a "WOT plug chop" correctly.

Have fun!

Jeff

canyncarvr · Mar 17, 2003

paul6585..re: 'low rpm bog'
Probably resulting from the air screw. Adjust it to best throttle response. Likely 'in' (richer) from the initial hi-idle setting. The kdx can go from crap to crisp with less than 1/4 turn of the air screw.

Tangentially......I've always liked that word......

Have fun, indeed!

dixie · Mar 17, 2003

yes you will afect jetting I live in NC I had same problem stock is a 160 main. and piolet is 48. Bikes are jetted for sea leavel your elavation location plays a big part on how lean to go. my setup a 155 main and 45 piolet. Then added the boyesen reeds. Piolet then drop to a 42 you add a pipe and silencer main drop to a 150 .and piolet to 40 . Riding for 8 years with this set up. THIS is only a guide to follow. Your result may very slightly ps. set your needle in the middle or next to top posetion and air screw at 1 1/2 to 1 3/4 turn and remeber oil brand and ratio has effect also YOU don't have to be a rocket scienceist Just go one step at a time and experament What works for one bike does not nessary work on anouther each has its own personally Hope I Have been so help.

spikes · Mar 18, 2003

Pilot Dixie... PILOT!

svmtbman · Mar 18, 2003

I went out for the 2nd ride since breakend this weekend and decided to leave the airbox cover on for now and ended up fouling the plug twice (the last time almost stranded me, the bike wouldn't start!) I'm going tomorrow and picking up a 155 main and 45 pilot and a few plugs to get this thing running right! Also, when I got home I thought I would check and see where the air screw was from the factory and it was only 3/4 of a turn out! This couldn't be helping either!

canyncarvr · Mar 18, 2003

The three best things you can do for yourself and your bike:

Learn how to jet your bike correctly.
Jet your bike correctly
Re-jet your bike when needed

Cheers!

svmtbman · Mar 20, 2003

OK, I went and picked up some jets today, they were out of 155 mains so I got a 158 main and a 45 pilot. I also raised the clip on my needle to the second from the top notch and removed the air box lid (on a '03 200). I then went out, warmed up the bike and installed a new plug and did a WOT throttle chop and pulled the plug. The plug was very white all the way to the base and some light colored smoke was rolling out of the pipe. So I went back and instlled the factory jets (160 main and 48 pilot) and left the lid off. After another new plug and WOT chop the plug still looks lean (very slight coloration at the base of the plug) Tomorrow I plan on installing a 162 main and see what the plug looks like then. From what I have read this just seems a little weird, everybody seems to have to go the other direction? Any imput?

svmtbman · Mar 21, 2003

I forgot to mention, the bike still has the stock pipe and silencer on it.

KDXFreestyle · Mar 21, 2003

my bike is all stock engine wise, anf I jyust made the airbox mod by drilling 3 1 inch holes inot the lid... you wanna tlak about friken performance..MAKE THE MOD, the bike runs, ands sounds like a 250 now. ITS INSANE! I just had to make that comment.........

svmtbman · Mar 22, 2003

Ok, got the bigger jets and this is what I ended up with to make the bike run great and the plugs to look right.
-Removed the airbox lid
-Stock Pipe
-162 main jet
-50 pilot jet
-air screw 1 turn out
-I currently have the needle clip on the 4th slot (needle raised 1 position from stock, not really sure it it runs better there than in the 3rd slot, gotta keep fiddling)
All in all the bike runs great, no flat spots or bogging, it will go to wheelie in 3rd from an idle using just the throttle.
I can't wait to do this all over again when I get a pipe! At least now I've got a good assortment of jets!

Jim Crenca · Mar 23, 2003

Go man go!

Remember that the jetting info is only a guide.
My 94 with FMF pipe, RB designs carb mod, and different needles needs way more main jet than most (usualy a 165) at sea level.
When you feel realy comfortable with jetting, start reading the RB Mods thread in archive section. Evem with a stock carb there are much better needles for crisper response.

Just one more airbox lid question

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