How to make your own air box lid pre-filter (step by step)

[maxfior]

I'm cheap. I don't like to spend money on stuff unless I really have to. So, when I saw the EHS air box pre-filter I thought I could make one myself. I ordered the filter from EHS (since that is the hard part to try and make a filter) and then went to work. If you are handy you should be able to do this with out much problem. Just take your time and be careful. The only thing that I needed on hand was a sheet of thin aluminum and some bolts, washers and lock-washers. The filter from EHS only cost $17.00 for regular mail.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05235.JPG
Here is the sheet that I used, you want to make sure that it is the right size.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05237.JPG
Filter looks like it'll fit nice. Now it's time to make a template, I used an old folder that I found lying around. Just take your time with this.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05242.JPG
Looks good, now it's time to cut the middle out...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05245.JPG
When using trusty razor blade make sure you be careful... You don't want to cut your fingers or face off... Then you won't be able to pull wicked hole shots in the summer time! :p
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05246.JPG
Now with the middle out you can work on tracing to the metal sheet. Tape it in place and then get out the marker.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05249.JPG
Trace away...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05251.JPG
After the trace job, clamp that sucker down and get out a 1/4 inch drill bit for making the holes. You'll also want to pop a hole at an edge for getting the scroll saw started...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05253.JPG
Holes drilled.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05254.JPG
Hole to start the middle cut with your scroll saw.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05255.JPG
Middle cut out, now it's time for the sides...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05257.JPG
Take your time when cutting out the rest... Make sure to re-position everything when cutting and clamp it down really well so that vibration is kept to a minimum.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05258.JPG
The cutting is finished and then I made sure to clean any sharp edges off... Don't want to cut anything...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05259.JPG
After the sharp edges were removed I then clamped the metal to the air box so that I could punch 1/4 holes properly.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05260.JPG
I also made a hole in the middle to start the saw... Now I carefully cut out the middle. Taking my time...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05261.JPG
Now that the middle is removed I clean the burrs off and get ready to assemble everything. Make sure that you use good bolts with washers on each side with a lock washer on the inside before the nut.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05263.JPG
Finished product... Looks pretty okay if I do say so myself... Now with the money I saved I can go buy some lunch, I'm hungry...
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05264.JPG
Bottom view.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05266.JPG
Ready for action! :)
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Any questions, please ask! This might not be for everyone, but I like to make things when I can. Good luck!

Max

[TheNewn]

Looks like it fits perfectly. And way cheaper than the arm and a leg they want for one. I'll have to do something like that for my R.

Good job, i prefer seeing custom mods done instead of just buy and bolt on kinda things.

[tar]

good job that looks nice and probably works better than their setup

[400exMO]

nice upgrade. I to love doing things like that myself and saving some cash. I've been kinda thinking about doing this, I just didn't know they made ehs sold those filters. Def. going to do it now.

[maxfior]

Thanks for all the nice comments guys! Yeah, it was fun to do and it's worth spending a little time to try yourself. I agree with you all that it's nice to do custom things yourself, at least, when you can... I don't think I'll try and make my own a-arms, haha :) If you guys plan on doing this, post pics on how yours turns out! Again, thanks guys and I hope more people try this, $17.00 (and if you have to by the steel, that'll cost maybe $5.00 more) is a small price to pay for a filter mod like this... Plus you get to say, "hey bub, yeah, I made that :)"

Max

[440challenger]

Nice, i did the same thing but used an old outerware i had laying around.
I just pop rivited it on. Not as nice looking as yours ,maybe lighter :blah:

[Brauap]

This is soo sweet! I had wanted 1 but didnt want to spend, what was it, $80? or ever $60 for a do-it-yourself, here, I can do it for 17 bucks! SWEET!!!


This is my next project.. :devil:
What did you have to jet it at?:confused:
Thanks Soo Much!:D

[hornetgod13]

Well done MAXFIOR! I'm impressed. :macho

I already have an EHS racing lid but, this is a cost effective alternative. Post this in the "How To" section as well if you haven't already.

Awesome job with it and it looks awesome!

[maxfior]

Originally posted by 440challenger
Nice, i did the same thing but used an old outerware i had laying around.
I just pop rivited it on. Not as nice looking as yours ,maybe lighter :blah:

Yeah, I was thinking about the pop rivits, but then I figured if the filter got all nasty I could just buy another for $17 bones and then toss it on quickly. Don't know about the weight though :) it's still pretty lite...

Max

[maxfior]

Originally posted by Brauap
This is soo sweet! I had wanted 1 but didnt want to spend, what was it, $80? or ever $60 for a do-it-yourself, here, I can do it for 17 bucks! SWEET!!!


This is my next project.. :devil:
What did you have to jet it at?:confused:
Thanks Soo Much!:D

Thanks man! Yeah, $17 bones. Well, assuming that you have a scrap piece of steel laying around... Make sure when you order the filter through EHS you tell them that you want the $2.00 shipping, otherwise they'll charge you $7.00 for the dang thing. And THAT is crazy. I'll post a picture of my bill for referance.
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http://www.maxfior.com/atv/400EX/MODS/AIRBOX/DSC05238.JPG
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As far as jetting, I just have the stock main in my carb and a #40 pilot jet. I'm going to add a pipe soon, so I'll move the main up and I might put a #42 in since it was a little hard to start it yesterday about 30 or so out in my shop. When I did get it started it ran very well and had a nice feeling to it. It's just really nice knowing that if mud and stuff splashes up it won't go directly in the air box.

Max

[maxfior]

Originally posted by hornetgod13
Well done MAXFIOR! I'm impressed. :macho

I already have an EHS racing lid but, this is a cost effective alternative. Post this in the "How To" section as well if you haven't already.

Thanks man! You got it, just trying to save people some cash! I'll post it in the how to's, good idea! I'm sure plenty of people can do this if they have the time! Thanks again!

Max

[maxfior]

I made a .PDF of my template for you guys to download. Just right click and save it to your desktop. Then cut it out and you'll be all set. Make sure you print it out in its full size. I also posted this whole write up in the "how to section" found over here:
http://www.exriders.com/vbb/showthread.php?s=&postid=3092376#post3092376
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Here is the .PDF
http://www.maxfior.com/atv/400EX/MODS/AIRBOX/400EX_template.pdf

Enjoy!

Max

[hornetgod13]

Originally posted by maxfior

Here is the .PDF
http://www.maxfior.com/atv/400EX/MODS/AIRBOX/400EX_template.pdf



Printed out just fine and lines up perfectly. Dry weather riders would be a fool not to do this if they had the tools and basic mechanical skills. Easy performance mod for less than 20 bucks!

[maxfior]

Originally posted by hornetgod13
Printed out just fine and lines up perfectly. Dry weather riders would be a fool not to do this if they had the tools and basic mechanical skills. Easy performance mod for less than 20 bucks!

Hornetgod13,

Thanks for printing it out and checking it out for everyone! I was hoping that it would line up okay, but I'm at my office working on computer junk (sort of behind working on computers because of the holidays) so I was not able to check it out on my quad. But I completely agree with you, it's pretty easy if you have a few tools.

1.) Scroll Saw
2.) Dremel tool for cleaning up edges
3.) Marker for writing, razor blade(s)
4.) Drill with a 1/4 drill bit and something a bit larger to start the cutting holes (3/4 maybe).
5.) nuts, bolts, washers, lock washers.

I think that's pretty much it, oh and maybe about an hour or so to cut things out. The printed template should make things go a little quicker, again, thanks for printing it out and checking it!

Max

[hornetgod13]

Originally posted by maxfior

As far as jetting, I just have the stock main in my carb and a #40 pilot jet. I'm going to add a pipe soon, so I'll move the main up and I might put a #42 in since it was a little hard to start it yesterday about 30 or so out in my shop. When I did get it started it ran very well and had a nice feeling to it. It's just really nice knowing that if mud and stuff splashes up it won't go directly in the air box.


I've done extensive jetting runs and I found the best jetting set up for me was a 40K pilot and 155K main jet. It's a stock 400ex motor with a timing key, UNI filter, HMF slip-on, and an EHS racing lid (identical to your custom lid). My riding temperature is between 50 and 90 degrees and altitude is between 100 feet and 1,000 feet. With the installation of the custom lid alone I would recommend bumping your pilot and main jets up one size.

As far as mud and water goes, I have not strayed away from mud or large puddles or heavy rain storms and was pleasantly surprised to see the custom lid preformed flawlessly. No water or mud intrusion and the air lid opening never got clogged. The only thing I would avoid is large bodies of water like deep river crossings.

[maxfior]

Originally posted by hornetgod13
I've done extensive jetting runs and I found the best jetting set up for me was a 40K pilot and 155K main jet. It's a stock 400ex motor with a timing key, UNI filter, HMF slip-on, and an EHS racing lid (identical to your custom lid). My riding temperature is between 50 and 90 degrees and altitude is between 100 feet and 1,000 feet. With the installation of the custom lid alone I would recommend bumping your pilot and main jets up one size.

As far as mud and water goes, I have not strayed away from mud or large puddles or heavy rain storms and was pleasantly surprised to see the custom lid preformed flawlessly. No water or mud intrusion and the air lid opening never got clogged. The only thing I would avoid is large bodies of water like deep river crossings.

Good stuff here... I have the #40 in, but I think I will go up a few sizes on the main. My engine is stock, I'd like to leave it that way for a while. I'll have to look into the timing key, did that work out well for you? And I think by the spring I'll finally pull the trigger on a pipe. I'm sure I'll get HMF and the quiet core for woods riding. I too will stay away from large bodies of water, that's never a good thing for a quad (IMO) and I'm happy to hear that your filter held up well, I know you ride some crazy stuff (as seen and read in some of your other posts) so thanks again for that information I (as well as others) find it VERY useful! :)

Max

[hornetgod13]

Originally posted by maxfior
My engine is stock, I'd like to leave it that way for a while. I'll have to look into the timing key, did that work out well for you?


The Curtis Sparks advanced timing key is another inexpensive way to beef up the performance of a 400ex motor with out sacrificing the engine durability. For less than $30.00. You can advance the timing 6 degrees giving your quad a snappier throttle response and more low end horsepower.

Here's a link to a step by step "How to" on the subject. It's pretty straight forward and took less than 30 minutes from start to finish.
http://www.atvriders.com/articles/timingkey400ex.html

[maxfior]

Originally posted by hornetgod13
The Curtis Sparks advanced timing key is another inexpensive way to beef up the performance of a 400ex motor with out sacrificing the engine durability. For less than $30.00. You can advance the timing 6 degrees giving your quad a snappier throttle response and more low end horsepower.

Here's a link to a step by step "How to" on the subject. It's pretty straight forward and took less than 30 minutes from start to finish.
http://www.atvriders.com/articles/timingkey400ex.html

Thanks, I'll have to look into that. Might be the next el cheapo mod for me! :p

Max

[400exrider707]

Timing keys are not recommended for modded motors, especially those with higher compression or an aftermarket CDI, as they produce a lot of extra heat. It's ok on a relatively stock motor (pipe/filter) beyond that I wouldn't use one, just my opinion.

The lid looks good. I did something similar to this when I had my 400EX. I bought a 3-pack of outerwears on ebay for go-cart filters, at around $10 shipped for the package of 3, cut one in half so it unrolled, and then used velcro to secure it to the top of my air box lid. Did the job and was around $10. Plus I still have two extra outerwears kicking around.

[maxfior]

Originally posted by 400exrider707
Timing keys are not recommended for modded motors, especially those with higher compression or an aftermarket CDI, as they produce a lot of extra heat. It's ok on a relatively stock motor (pipe/filter) beyond that I wouldn't use one, just my opinion.

The lid looks good. I did something similar to this when I had my 400EX. I bought a 3-pack of outerwears on ebay for go-cart filters, at around $10 shipped for the package of 3, cut one in half so it unrolled, and then used velcro to secure it to the top of my air box lid. Did the job and was around $10. Plus I still have two extra outerwears kicking around.

That's cool man, it's all about saving some coin and doing things yourself! It feels good to... To look back at your work :)

With the timing key... I don't know if I'll install it or not. I'm going to get my pipe first and then see. So far, my 400EX does what I need it to do...

Max

[hornetgod13]

Originally posted by 400exrider707
Timing keys are not recommended for modded motors, especially those with higher compression or an aftermarket CDI, as they produce a lot of extra heat. It's ok on a relatively stock motor (pipe/filter) beyond that I wouldn't use one, just my opinion.


With an aftermarket exhaust and filter as well as a moded air box lid, a timing key will not add enough heat to even be a concern. I have an oil temperature dip stick and I saw NO rise in the oil temperature.

[maxfior]

Originally posted by hornetgod13
With an aftermarket exhaust and filter as well as a moded air box lid, a timing key will not add enough heat to even be a concern. I have an oil temperature dip stick and I saw NO rise in the oil temperature.

...Speaking of that dipstick, (which is awesome) where did you get that at, I'd like to pick one up, that's a really good idea!

Max

[hornetgod13]

Originally posted by maxfior
...Speaking of that dipstick, (which is awesome) where did you get that at, I'd like to pick one up, that's a really good idea!

Max

I got it off the XR's only website at:
http://www.xrsonly.com/content/index.php?page=shop.product_details&flypage=shop.flypage&product_id=1363&category_id=127&manufacturer_id=0&option=com_virtuemart&Itemid=77
It's cost $39.95. It's specifically made for the 400EX and is long enough to check the oil level as well. They sell both red or silver colored ones.

is it all metal or what?

[maxfior]

Yeah, that dip stick is awesome, I'm going to order one. It's always a good idea to keep an eye on the temp of an air cooled engine. What sort of temps to you see. In normal riding conditions...? And thanks for that link!

Max

[hornetgod13]

Originally posted by FoxHondaRider
is it all metal or what?

It's made of metal and impact resistant glass. Very durable construction.

[hornetgod13]

Originally posted by maxfior
What sort of temps to you see. In normal riding conditions...?


It normally ranges between 180 to 250. It really depends on riding temp and how much airflow over the motor. Anything around 300 degrees or higher is a bad thing.

[maxfior]

Originally posted by hornetgod13
Anything around 300 degrees or higher is a bad thing.

LOL! Yeah, engine meltdown... I know that some car engines run pretty hot too... I think that dip stick is a pretty cool thing, I'll have to order it on Wednesday. Thanks again!

Max

[dsm_racing]

I've got my filter ordered. I'll post up when I get it done. Nice link on the temp gauge.

[sc400ex_rider]

i just got the sparks key and told them my mods and they said it was ok to run 11.1 comp. piston. to them high comp. is 12.5 and over. im running standard bore so heat is not an issue. check my sig i got only $600 in my motor and its a diff machine.:eek2: :blah: :D