I saw filters for sale that can be inserted into one inch holes drilled in the lid. My question, is it even worth it to drill holes in the lid? My machine (250X) is completely stock except for a k&n filter.

 

Don't drill holes in the airbox. Just take off the lid and either buy some foam and make a cover for the airbox or buy an Outerwares lid. You will see significant power gains from this mod, just don't forget to richen up the jetting or you will sieze the motor.

 

Any time you increase the air flow to your engine it is worth while.Of course, if that is your only other modification the bike won't exactly run out from under you, but you should notice a difference in response. You may need to rejet after opening up the air box. On my Warrior I run a Motoforce vented lid from Jas Lucky. It allows 90% of the flow of a lidless airbox while still giving some water protection. It is also made of clear plastic so the condition of the filter may be checked. I don't know whether a model is available for your ride

 

Well if you drill the holes in your airbox lid you will have more air flow. You might have to rejet your carbs but probably not if you still have the stock pipe and muffler. I'd add a pipe kit and rejet and make the most out of that small motor.

 

The drilled hole filters work great! I highly recommend them over the Outerwear box covers. If the Outerwear slips or comes off, you are screwed!

Be sure to put some hole/filters on the side of the box as well as the lid. This will ensure an even flow of air to the entire filter. I recommend no less than 12 hole filters.

BE SURE TO INSTALL THESE HOLE/FILTERS ONLY AFTER YOU HAVE PUT AN AFTERMARKET (K&N OR PRO-DESIGN) FILTER ON!!! The stock Banshee filter sucks and these additional filters will allow too much air to come into the engine. Personally, I recommend the Pro-Design set-up for all around use.

Anyway, the neat part of these hole/filters is you only have to pull the little blue sponges out to clean them. To increase the air flow on my Banshee, I sliced the thickness of each sponge in half with a pair of scissors. This increased the airflow even more, but still allowed some effective filtering.

Remember...you must re-jet after increasing the airflow or you will run too lean and risk burning up the engine. You will probably have to go from the stock .190 jets to at least a .270 jet if you still have the stock pipes. If you have a quality aftermarket pipe, I would start at about .290 at an elevation of 1000 feet. Do a plug check and fine tune your jetting. Don't waste your money on any "aftermarket jet kits." They are nothing more than a set of needles and jets. Bottom line is if you haven't modified the engine (ported, polished, shaved head, coolhead, etc.), you will most likely only have to increase the Pilot (Idle) jet one size and the Main jets several sizes to about .290. Don't mess with the needle clip placement unless you re-work the engine.

Good luck!

 

Good post and congratulations on da gorgeous wife Rob!

 

I hate to disagree with Rob, but here goes!!

We put a complete head, carburetor and airbox assembly (with filter and stock snorkel) on the flow bench to check out what works best for airbox lid mods. Those little one inch foam filters actually don't flow any better than the stock lid with no holes in it.....

Okay, wait a minute before you all start screaming!

Think of it this way -- air follows the path of least resistance (just like water). With those small holes, the path of least resistance is STILL the snorkel. Still don't believe me?? Grab a drink cup with a lid and a straw. Now, cut a hole in the lid that's about 2x the size of the straw. Slide the straw 1/2 way out of the cup. Fill the cup with water and turn it over -- did the water drain out of the hole you cut, or the straw? It all come out of the bigger hole, and just used the smaller one for "suction".
The straw is those little vents, the hole you cut is the snorkel on your lid.

Sorry for the long description, but now I'll cut to the chase!

The only way to increase flow to the airbox is either pull the lid off, or to open a hole in the lid which is larger in volume to the snorkel (which is what the Motoforce lid does).

Yes, they do make a Motoforce lid for the 250X. James Lucky, White Brothers, and Powroll carry them.

 

Pam,

I am going to make history here, but for the first time, I disagree with you...Sorry...

The 1" filters definately make a difference! They absolutely increase your air flow. A simple way to prove this is to install them. You will immediately begin to have dirt collect on them (through and through, not just on the top). Additionally, your plug color will change since the engine is running leaner due to the increased air flow. I promise.

While Pam is correct in electrical theory, air flow is not as linear as conductivity over a metallic conducter or passage of water. In other words, once the snorkle begins to fill with air, the air will look for other places to enter. If Pam's theory is correct, the air going into the snorkle will be sucked out the 1" filters, therefore, the engine would run too rich and choke itself out. Just the opposite occurs, the engine runs leaner due to the increased airflow opportunity.

I hope this makes sense!

Use the filters. In my opnion, they work!

 

i agree, but the best thing i have seen to get more air flow and still keep out the dirt is an outerwears for the airbox. you take off the lid, and put some velcro around the box and the outerwears attaches to it. you get the increased air flow, but less dirt(works great for sand duners).

but i still beleive the best is to just take it off and clean you filter after every one or two rides. you can never clean your filter enough.

 

Personally I don't see why you will ruin a good lid by putting holes in it (It nice to put it on when washing your bike). You might-as-well just take the lid off because you will gain much more flow and it will be even and undisrupted, thus giving you much more power. But then stuff will get in you say, well if you go through deep enough water those vents won't keep it out anyway and as far as dust or dirt, how about running a good UNI or Durablue foam filter and put a clean one on it after each ride as you should do anyway. Also I know what you think about the vents and foam covers, etc. I've tried them all and even a full foam cover doesn't flow well, and I had a lid with the vents in it (It came with my bike), and I also cut out the entire side next to the filter (As a motoforce lid does). Well motoforce claims there lid flows as much air as just having the airbox removed does. That may be true, BUT the flow is distrupted (Not directed smoothly into the intake system) enough that it still wouldn't allow my bike to run well at all with the jetting I run with the lid removed.

Long story short, don't waste your time and money, just remove the lid if you don't ride down the middle of a river, run a quality foam filter and keep it clean...

As far a K&N with outerwears. On a dino it can be seen that a good 2-stage foam filter flows more air than a K&N with an Outerwears, and filters as good or better...

Sickman