Airbox Tip for XR owners

Here's a tip for XR owners.

The first thing anyone does when they first purchase a Honda XR, is remove the snorkle or baffle in the airbox.

It really helps the bike breathe, but I was a little concerned about junk making it's way in the airbox. I wanted to put filtration material on the opening but wanted something a little more professional looking than duct tape.

Here's what I did:

Go down to Wal-Mart and get a Rubbermaid Servin' Saver Plus storage bowl (the 750mL size). It is rectangular and the top is a perfect fit for the opening on the airboxes of XR200's and 250's. You just have to cut out the center section out with a utility or exacto knife. It is even detented for easy cutting!

While at the store, pick up a pack of Vent Filters. I got the Electrostatic Register Filtration type that are 4" by 12". I cut them in half and it fits over the airbox opening perfectly. Then you just place the top of the storage bowl over that!

You have an efficient, sano filter. You can even put a little filter oil or WD40 on it to help with dust.

I know it works for XR200 and XR250. I probably works for other XR's. The bowl top fit snug in between the frame rails.

Try it out, it works great!!

I just have the top of my airbox open, and clean and oil the filter after every ride. I make sure the drain is clear and free of dirt, so water, if it ever gets in there, will drain out. I don't see any other reason to filter that opening, when there is a filter before the carb!

I feel a little out of place reponding to something Corey said prior to Keithco responding but I've got things to do and I can't wait any longer.

I agree with Corey. A clean and properly oiled filter is all that is required. I've ridden in just about every condition and have never seen a time when something additional was needed. You've put some thought into it and I commend you for that but I feel some of these are counter productive and actually add restriction rather than what is desired, that being less restriction and a more free flowing intake.

The snorkle removal mod is beneficial but it's only one of several things that can be and should be done to a stock XR. Performing the "Gordon Mods" should be required of all new XR owners. Not only do they allow the XR to perform at a higher level but they afford the owner an opportunity to better understand thier new bike and the affects intake and exhaust has on the engine.

For more info on these mods search this site or check out the post - snorkle hole. Kev XR has a link to them in his reply.

Have fun.

I'm a big advocate of running a sheet of 3/4" oiled pre-filter foam over the top of the airbox. The inside of my airbox is really clean and the filter stays pretty clean.

I can open the side panel and pull out the pre-filter if needed. I've run the bike with and without it and can't tell the difference.

I have photos of it posted in the files section of the XR400 group on

I can see a huge benefit in desert conditions. One of the areas we ride (near Bend, OR) is all volcanic dust and it really clings to an air filter. A prefilter with washable element would be quite beneficial for our multi day camping trips. One day of riding and your filter is plugged, a prefilter would be easier than replacing the filter in the middle of the weekend.


A little idea you might think about, Kevin. Your airbox inside is clean all the time? What about putting a thin layer of grease around the inside walls ot the box, so the dust/dirt sticks to it and not all on the pre-filter, restricting air flow. Dirt will still get trapped in the stock air filter itself, but if the inside walls stay clean, then why run a filter inside at all? If I was riding in the dust that thick, then I could see your point, by taking the pre-filter out, during a race only situation. I'm not dogging your idea, just another thought to go with it.

What ever...

I was shown using a prefilter by my friend in Oregon.

We were riding in areas with really thick red dust.

One rider could obscure the trail for 5 minutes in spots.

It's more pourous than the main filter, it just catches some of the dirt on the way to the filter.

Take a look at the photos.

I've recently completed all of Gordon's mods and have not had the chance to try it out yet except for up and down my very short street. Incredible how the front wheel pulls right up now. I ground out the header welds, drilled 3 holes in the exhaust tip plate and ran a uni-filter last year. On my last ride of last year I pulled the snorkle out and felt the motor was not getting enough gas for the increased air it was getting. This really confirmed the need to re-jet (60 & 160) I don't understand how other xr owners pull there snorkle without rejetting and feel that it runs better. Mine sure didn't until I re-jetted. As for the snorkle hole I cut the bottom of a tupperware container and put it in the hole. I guess the tupperware walls coming down into the airbox could act as a throat like the original snorkel only a much larger openning at the top. We cross a fair amount of rivers up here in Canada so I'm hoping the top ridge of the tuperware outside the top of the box will help prevent any water from simply roling down into the snorkle hole. I cut the center out of the tuperware lid so I could snap down a screen on the tuperware. This might create an inconvinience in the future due to the fact I will need to take my seat off to clean that screen. Trial & error I guess. Now if we can only get ride of the three feet of snow we have up here.

Good points and well taken. I do not want anyone to take this tip for an excuse for not doing good bike maintenance. I clean my filter very regularly and make sure it has a good seal with the box. It is just a personal preference and the mesh is not a very restrictive material, in addition, it is a non-destructive mod.

An important point when making any mods such as this is, you need to do plug checks after ANY mod to make sure you are not running either to rich or lean. In fact, when riding in wet, muddy conditions like what we are experiencing now (South-East, we have had LOTS of rain) the filter stays really clean and the mesh cover doesn't really catch a lot. Honda does a good job with the top of the airbox and the mating surfaces to obstruct debris.

This is a really good site. Keep the replies coming! I am new to four-strokes and it has been a lot of fun learning all over again. Where are the "Gordon mods" posted?

For really dusty conditions or extended rides where you may not want to clean your filter at your overnight stop I have had good results using a large womens footlet (like a stocking for just the foot) stretched over the filter. Its a poor mans filter skin which can be removed leaving your filter faily clean, cuts down on filter cleaning (but isnt a substitute)and no one likes cleaning filters. I have done the gordon mods, actually they are performed by the dealer at time of purchase hear in Australia except for the header welds which u have to do yourself, I could not tell the difference with the footlet installed but this wasnt a race situation! :)

Jesus....I just read the "Gordon Mods" for the first time. So much for eyeballin' things such as header weld grinding!

"I'm not worthy!"

I would like to request my return to "newbie" status after that humbling read :)

I have had great success with stretching a filterskin over the airbox opening. A day of very dusty riding and the airfilter appears very clean. To me it saves time and work while providing maximum engine protection.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Kev_XR
      If you own an XR250, many of these tips will apply, however, the carburator jet sizes will be different.
      It really helps others answer your questions.
      I will fix them as time allows.
      Until then the Search Feature and enter "kevin's xr400 mods".
      The results will bring up most of the links.
      Here are some frequently asked questions I have answered before.
      Which XR should I buy?
      The longer the straights, the taller the hills, the deeper the sand; the bigger XR you want. The tighter the trail, the smaller hills, firmer terrain; the smaller XR you want.
      The XR400 has a great motor that will pull you almost anywhere. You can be sloppy on a hill climb on an XR400, where you have to keep the 250 singing. The XR400 weight is most noticable when you drop it or try to stop it going down a long downhill. (Moooomentum!)
      The XR250 feels like a mtn bike compared to the XR400. My friend rode his XR250 for years before decided he needed more power. Even then you can add a 300 kit and get good power.
      If you were heading to ride fireroads in Baja, I'd tell you to get the 600/650.
      To the tight woods, get the 250.
      A lot of both, the 400.
      Dual-sporting? Go bigger for more freeway, but don't show up at the trailhead with too big of a bike.
      All of the XR's are great. Pick the one that fits your needs.
      Gordon's Mods for XR400 (Uncorking the bottle up performance)
      Gordon's Mods for XR400
      XR400 History
      The changes to the XR400 have been listed here several times. This list appears to be complete.
      In addition, HairyScary discusses how to tell if a part has been updated by the part number. Good tip!
      XR400 history
      Getting the Spark plug out
      It seems the MotionPro spark plug socket does not work on the XR400R, but works on the XR250R.
      There is an OEM tool kit being sold on eBay that seems to work.
      717448 XR400 oil change
      Here is a way to make changing the oil much cleaner.
      This tips is really handy if you have a skid plate.
      XR400 oil change
      XR400 FAQ by Paul Gortmaker
      Paul usually has very good info.
      Small bolts
      BE CAREFULL with the bolts on the oil filter cover!
      An oil covered bolt will not torque at the same rate as a dry bolt.
      The friction doesn't build up, the force simply builds until the threads strip.
      This is the reason many people strip out these bolts.
      Here is an execllent website on bolts, oil, and misc values.
      Did you ever wonder why a 8mm box wrench is half as long as a 18mm box wrench?
      It is shorter as most 8mm bolts cannot take very much torque.
      I highly recommend getting getting an 1/4" socket set.
      I bought the Craftsman set at Orchard (owned by Sears), which tends to sell them for less.
      What is the Snorkle?
      This place has a description and pic, it's easy after you pull the seat. I siliconed a piece of coarse screen (fiberglass) over mine to keep bugs and stuff out. - NORTEXT
      717439 XR400/250 Pre-Filter
      After pulling the snorkle, there is a big hole on the top of your XR400. My friend showed me this prefilter trick.
      767409 XR400 Engine Bog, Pilot jet, and the Fuel Screw
      On XR400's twisting the throttle from fully closed to wide open will cause the engine to "bog" or in some cases die.
      Engine Bog, Pilot jet, and the Fuel Screw
      831305 Valve adjustment (Am I retarded...)
      Inspect and adjust valve clearance while the engine is cold (35C, 95F).
      Valve adjustment
      389095 bigger jets (Lists stock jet sizes.)
      96-97 XR400's were jetted assuming you would remove the intake and exhaust snorkel.
      98 and later XR's were jetted assuming you would leave them in.
      bigger jets
      739907 Cheap Tool for Setting the Fork Oil Height
      There are some really nice tools out there for doing this job.
      This tool costs $4.49 at Kragen.
      Cheap Tool
      392932 high altitude jetting
      There are two big factors for jetting, elevation and temperature.
      high altitude jetting
      Allen screws for the XR400 carb
      This lists the screws you need to convert the XR400 carb to use allen screws.
      Allen screws
      Screws for the brake and clutch after removing the stock handguards
      TBD - There is a post with the shorter screw part numbers for after the stock handguards are removed. Use search.
      Very quick engine hop up
      This is a very minimal change that should take less than an hour.
      Most of that time is removing the float bowl (3 screws).
      If you decide to do the full "Gordon's Mods" later, you will need to replace the jets again.
      o Pull the intake snorkle.
      o Add a UniFilter.
      o Pilot jet to 55, main jet to 155. (Assuming sea level and moderate air temps.)
      Source: Motocross Action magazine.
      Quick engine hop up
      Gordon's mods
      Baja Designs Baja Baffle with 96' spark arrestor.
      Pull the intake snorkle, UniFilter, 60 pilot jet, 162 main jet.
      (Depending on altitude and temp.)
      What to add to a new XR400 or XR250?
      Acerbis wrap around style handguards (saves levers and bars as they don't dig in)
      Baja Designs skid plate (Made by Utah Sports Cycle)
      Acerbis fork/disc protector
      Grease headset and rear linkage
      Spend you money on the suspension, not a pipe!
      First get some stiffer fork springs (96-97, 98-99 years)
      Fork revalve (cost: 2 qts of oil & time)
      Shock revalve (cost: oil, nitrogen, shim stack, friend who knows shocks)
      Jetting for Altitude (XR400)
      Assuming at sea level and 68 degrees, you would use a 60 pilot and 162 main.
      At 5000 feet and 68 degrees.
      Jettting correction:
      5000 feet and 68 degrees.
      Main 0.96 * 162 = 155 -> 155 main
      Pilot 0.92 * 60 = 50.6 -> 55 pilot
      Due to your elevation, you have less air and less fuel.
      Your bike will not behave the same as a bike at sealevel.
      First, check the fuel screw. If it does not affect the idle speed, you have the wrong one.
      kevin's xr400 mods
    • By Child
      Can we make a sticky thread of pictures? I've done search for pics but I want to see all sorts of bikes just for ideas on stuff without having to go through tons of threads. Not trying to sound whiny or anything, but I think it would be nice to do what they do in the CRF250X forums with a sticky thread of just pics, no comments or anything. Think we can get one of those rolling here?
    • By kawamatt2
      Ok guys, add one more to the list of riders attempting the USD fork swap to an XR frame. Quite a bit of research here on TT and ebay hunting brought me a pretty good deal on a set of forks, triples, and stem from a 00' CR 250.
      There are a few different options for adapting CR style forks to an XR. Bushings for upper and lower CR triples can be made to allow use of the stock XR stem. Specialty bearings can also be purchased to allow use of the stock CR stem in the XR neck. And finally what seems to be the most common; modification of the stock CR stem to allow use of XR sized bearings.
      I obviously chose to pursue the third option for a few reasons, the most prominent of which is serviceability. I wanted to keep as many wear items at possible as stock parts. This has two advantages; availability and price of replacement parts. $45 dollar a pop "specialty" thin section tapered bearings don't sound too appealing especially when being used on a 12 year old dirtbike.
      So now we can get to the meat of the issue; modification of the CR stem. I should begin by saying that i am NOT a draftsman. I've taken a few classes on engineering measurements but am far from an expert and probably only mildly proficient reverse modeling components. With that said, the first order of business was comparing an XR stem and bearings to a CR stem and bearings. Shown below.

      A little closer look at the XR setup.

      And the CR setup.

      Now to get out the calipers and model up the stock CR piece. I used a cheaper set of calipers and suspect their tolerance is +/- .01mm. Good enough for gov'ment work though! All dimensions in millimeters.

      Now to modify the CR stem to work with the XR bearings while remaining compatible with CR triple trees. There are a few things to say about why i did some things the way i did but most of the thoughts are included in the notes section of the drawing.

      With a resized stem we run into the problem of mounting the top triple clamp. The hole is too large for the stem. An insert bushing must be made to resize the hole in the clamp.

      Finally what the stem and bushing look like together.

      Last one. The difference in how the top triple clamp is located on the stem. The CR is equipped with a chamfer that provides a stop for the tree while the XR's triple appears to be limited only by the threads for the castle nut.

      So... would like to hear your opinions on the execution of the stem modification and bushing. I think having these drawings will make it simpler to have the modifications performed as opposed to asking the machinist to completely reverse engineer the part him/herself.
      And a final query: Anyone know the thread callout for the two threaded portion of a stock XR steering stem? My drawings show the outside diameter of the threaded portions and i have a cheap plastic pitch gauge that tells me a pitch of 1.0 but i am looking for something more concrete than what i have.
      Thanks for your thoughts and opinions.
    • By ATJ_Number_1
      I'm on strike 2 here but thankfully this isn't baseball.
      The reasoning and my history. If you haven't figured it out yet I've done a crap load of work on these motors over the last 7 years but they have had 4 wheels around them. In the EX world there are a lot of carburetor options and although many are great there's a cheap alternative that runs 95% as hard as the high dollar options, some even liking it better then aftermarket. When I joined up here in the 2 wheel club I was shocked that the only accepted option was $400 for a 36mm Mikuni Pumper that isn't any bigger then stock! That cheap alternative for the EX is an 04-05 trx450r carb. It's 42mm round slide Kiehin piston-valve with accelerator pump and a mildly modded 400 loves it with a surprisingly strong bottom end yet. Yes I said 42mm!
      So as I build my XR4 I already know that I'd be shooting myself in the foot if I settled on a 36mm carb because I like bigger bores and cams and this motor likes bigger carbs. Makes sense, it is 400cc. Don't get me wrong though, the Mikuni is a real nice pumper for a stock bike and would seem fine on a well modded machine too but this 4 stroke is like every other one in the world in regards to when you go big inside, you want to go bigger outside or you're missing out.
      Whether the info is appreciated or scoffed at I'll post up my findings one by one as I try to find viable alternatives. When I say viable I mean still being able to use the stock environment and not needing a ton of work. I'm sure collectively this is not a new idea to search for such a beast but I enjoy a good project and I like cheap alternatives when they produce results.
      Currently the "test bike" is a 2000 Xr400r, snorkel removed, Uni filter, stock engine, stock headpipe and a 4" supertrapp slip-on with 11 discs.
    • By XL100allnightlong
      Just wondering if there is any tricks to polishing the stock headers on an 02 xr 400 to bring back the original copper color? If not ceramic coating them sounds like an option?