Airbox snorkel size

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Airbox snorkel size

Postby kdxdazz » 09:14 pm Oct 07 2018

Still struggling to get my bike running well so trying to put as much as I can back to standard. Can somebody tell me the snorkel size for kdx220 1997 model so I can patch up the previous owners cut out,
Something doesn't ring true about making airbox lids large, if you look at a ktm690 lid you couldn't even put a golf ball down the openings and that makes 65 horsepower, I used to own an rgv250, the airbox openings on that is not even ping pong ball size and that made 60hp. I was young and silly at the time, I drilled lots of holes in the airbox lid and lost all low end response, open to opinions on why everybody is modifying airbox's
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Re: Airbox snorkel size

Postby Jason » 10:51 pm Oct 07 2018

More oxygen, more power

The engine has to be able to draw in the air and room for it.
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Airbox snorkel size

Postby Julien D » 10:59 pm Oct 07 2018

Opening the KDX airbox lid is almost always beneficial unless you ride through a lot of water crossing and such and are worried about water/mud getting up under the seat into the airbox. Whatever is going on with your bike, the only way restricting the airbox is going to help is if you are already running too lean. If it's lean because of too much airflow, fattening the jets is a better answer than restricting the airflow.
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Re: Airbox snorkel size

Postby kdxdazz » 03:02 am Oct 08 2018

was hoping for a more technical answer than Bigger is Better,what about resonance frequency . i find it hard to believe that every motorcycle company on earth got it wrong, most bikes run a 2 plenum system for the lid rather than just 1, if bigger is better was true then a 38mm carb would be better than a 36mm and so on but we know that is not the case due to air velocity
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Re: Airbox snorkel size

Postby Jason » 05:27 am Oct 08 2018

Have you ever seen a MX bike's air box? You know what the lid is on my YZ and KX's? ... the bottom of the seat

bigger carb is for high rpm

smaller carb is for low RPM
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Airbox snorkel size

Postby Julien D » 06:10 am Oct 08 2018

So here is the thing, and it doesn't have to be all technical. A two stroke engine works like a big air pump. You want the carb to be the restricting factor, not the intake before it. The snorkel is there for protection against water, not for any performance enhancing reasons. Also note Jason's very accurate point about MX bikes generally not having such restrictions. The KDX has it there as it is designed for trails only, where riders are more likely to encounter water/mud crossings more frequently than a straight MX bike.

Also note, removing the lid WILL allow more airflow, which in turn will require more fuel. If your bike has not been jetted for the way it is currently configured, I would highly recommend following the jetting guide which is stickied in the jets and needles section here.
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Re: Airbox snorkel size

Postby kdxdazz » 08:26 am Oct 08 2018

I also own a yz426 which has an open airbox and a wr450 which has a very small opening. Comparing to an mx bike is fruitless as trail riders we are not riding in the upper rpm constantly, I've followed the jetting guides in here but it's not working for me which leads me to believe it's not a jetting problem and also I believe jetting at the equator where I am is not the same as other locations
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Airbox snorkel size

Postby cornishwrecker220 » 09:53 am Oct 08 2018

My 220 motor has been breathed upon ( ports , squish etc ) & I also run a 35mm carb off a KX ..the jetting with the air box lid removed was difficult as it performed different up toward the top rpm range than below ....after much messing around with jets etc we reinstalled the air box lid & ran it again on the dyno ....to cut a long story short my 220 ran at its best with a great spread of power right off throttle with the lid installed but with the snorkel removed & the addition of x3 one inch holes drilled in the top of the lid next to the snorkel opening .....these holes were then filled by using x3 small Uni Filters pushed into place ....my 220 kicks out a healthy 40bhp at the rear wheel ..

My advice is if you are struggling to get your 220 to run correctly I doubt it'll be because the lid has the snorkel removed or the opening opened up slightly ...

Can you be more specific in explaining what symptoms you are getting regarding your jetting issues ?

As a starting point ... 40/42 pilot jet ...148 /152 main ....needle in the 4th from top position ...fresh fuel at 40.1 mix ..new plug ..clean air filter ... Air screw 1.5 turns out ...check float height ...inspect overflow pipes inc fuel tank breather pipe...

Hope the above helps.

If you are running a boyesen rad valve then you will need to go down a size on the pilot ...

Hang about .....I've just read your other post & you say your bike is the SR version ..?

The above settings I posted are for the enduro H series 220 & not for the SR ....as the SR has the much smaller carb than that of the 33mm one fitted to the enduro 220 .
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Re: Airbox snorkel size

Postby ericr » 10:06 am Oct 08 2018

I had just read this article about bigger not necessarily being better for airbox lids... https://tinyurl.com/y7my4n9p
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Airbox snorkel size

Postby raygun » 10:34 am Oct 08 2018

You may have checked this but did you check or replace the jet block gasket? My bike was all sorts of inconsistent until I replaced mine. It was old and brittle.
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Airbox snorkel size

Postby pumpguy » 11:36 am Oct 08 2018

To answer the OP's specific question, the snorkel dimensions are as follows:

Cross section of opening:
3.150" wide, 0 .7" across. The vertical section inside the air box has a .175" thick divider across the 0.7" dimension.

Minimum overall length: 3.7" This length includes the vertical portion inside the air box, and the horizontal portion above the lid. The horizontal air inlet portion faces forward, toward the fuel tank. The snorkel outlet inside the air box is at an angle, maybe 55 degrees or so, up from horizontal.

Hope this helps.
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Re: Airbox snorkel size

Postby Tyl3r » 12:00 pm Oct 08 2018

Just a thought... I went through an extremely similar sounding situation with my 220 when I first got it. Went through a million things until one day I was riding it around and BOOM, it locked up because the stock cast piston skirt gave way. Rebuilt the entire motor and had the cylinder reworked. Put it back to together and it runs like a champ.
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Re: Airbox snorkel size

Postby Julien D » 05:16 pm Oct 08 2018

Tyl3r wrote:Just a thought... I went through an extremely similar sounding situation with my 220 when I first got it. Went through a million things until one day I was riding it around and BOOM, it locked up because the stock cast piston skirt gave way. Rebuilt the entire motor and had the cylinder reworked. Put it back to together and it runs like a champ.



This is an important thing to check on any and every KDX220.
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Re: Airbox snorkel size

Postby Julien D » 05:54 pm Oct 08 2018

ericr wrote:I had just read this article about bigger not necessarily being better for airbox lids... https://tinyurl.com/y7my4n9p


For the record, that article is actually an advertisement for a pricey product to give you an "adjustable" airbox opening.
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Re: Airbox snorkel size

Postby kdxdazz » 10:09 pm Oct 08 2018

thankyou for the dimensions pumpguy. to describe my problem my bike is running extremley rich at idle to 1/3 throttle with almost zero power and throttle response.it s a 1997 kdx220sr with a 36mm RB carb. the jetting is 1173l needle 2nd clip with 35 pilot jet,150 main jet,won't idle unless the airscrew is out more than 2 turns. oil ratio 35-1, run it on 95 e10 as straight gasoline is too rich for it. engine completely rebuilt,new factory reeds, new jet block gasket, float height set using clear tube method which gives a float height of 19mm, wiseco piston, tried many different needles including jd red needle and they are all too rich, welded a bung in the exhaust to put my wideband AFR and getting 12:1 at idle and quarter throttle. conditions here in thailand are about 35 degrees celsius,90 percent humidity,elevation about 3000ft. smokes quite a bit at idle but now runs smoke free and very strong in the upper RPM, pings slightly but i think that is due more to me trying 91 e10 to lean it out further
i have ordered a spark gap tester to see if there is any problems with my ignition system but as it stands i am getting 12k ohms on the ignition coil secondary windings and almost zero on the primary windings but the new coil i purchased also has the same readings so might be a problem with my multimeter,will go buy some resistors today to check my multimeter is accurate
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Re: Airbox snorkel size

Postby Jason » 10:30 pm Oct 08 2018

Just for fun, try adjusting the float level a little to make it leaner, then see how it is affected.
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: Airbox snorkel size

Postby kdxdazz » 10:36 pm Oct 08 2018

did that already jason, i adjusted all the way up to 21mm but then seemed like it was starving for fuel in the upper rpm's, when i say starving i mean it would just cut out like the fuel bowl was empty,wait a few seconds then it would fill up and good to go again. i might try it again as you say just to confirm the first test wasn't flawed as that was before my engine rebuild,i have a 32 pilot jet i might try as well
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Re: Airbox snorkel size

Postby kdxdazz » 01:50 am Oct 09 2018

Some reading for the technically minded and confirms that manufacturers didn't get it wrong
http://www.saltmine.org.uk/randy/airboxdesign.html
https://motorcycleinfo.calsci.com/Airboxes.html
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Re: Airbox snorkel size

Postby ericr » 12:05 pm Oct 10 2018

kdxdazz wrote:Some reading for the technically minded and confirms that manufacturers didn't get it wrong
http://www.saltmine.org.uk/randy/airboxdesign.html
https://motorcycleinfo.calsci.com/Airboxes.html


Interesting. So, there probably is an optimum snorkel size for my bike with RB Design mods. Too bad I'm not an engineer to figure it out...
'02 KDX 200, '02 KDX 220, '18 KLX 140G
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Re: Airbox snorkel size

Postby jjavaman » 12:22 pm Oct 10 2018

ericr wrote:
kdxdazz wrote:Some reading for the technically minded and confirms that manufacturers didn't get it wrong
http://www.saltmine.org.uk/randy/airboxdesign.html
https://motorcycleinfo.calsci.com/Airboxes.html


Interesting. So, there probably is an optimum snorkel size for my bike with RB Design mods. Too bad I'm not an engineer to figure it out...



I kinda think when the guy (RB) who designed the RB carb and head mod advise’s us to remove the snorkel and lid of the air box , we should listen to him rather then some theories on 4t or streetbikes. I personally can’t see how getting less air Into my 2t would improve performance? I’m sure there’s got to be someone on here who has the RB mods done and tired it both ways?
97-220 with a PC pipe. 2015- RB carb and head mod
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