DIY - Removing the air filter box (oh my!)

[kkim]

try looking in the jetting database and see if anyone has a setup close to what you are thinking of and use their setup as a guide. you'll need to fine tune as you go.

I will say, once you start rejetting you 'll have your fill of modding as it's a never ending job looking to the prefect combination as you experiment with different setups.

either jet kit would work.. they are both tools. You need to learn to use those tools effectively for max output.

my suggestion is to leave the bike stock for now and shim your needles... pull the snorkel when you shim.

when you have a full exhaust, then pull the airbox and install a jet kit at that time.

[Hokie11]

aw, but ive already shimmed and desnorkeled i want to do more! but dont exactly want to spend 500 on an areaP YET.. i will maybe for xmas but not now

[kkim]

if you yank the airbox, I don't now anyone who has done so that is still using the stock airbox. You would need to change the main jets. (costs about $5 each) I'd suggest using 110 Keihins to start and take plug readings to figure out if you need to go up or down from there.

that should keep you really busy.

if you buy a jet kit, be sure to get one made for no airbox.

[Hokie11]

you mean stock exhaust?

i do plan on getting the dynojet stage 2 kit, didnt know there were ones specifically for no airbox.. is the dynojet one ok?

[kkim]

yeah, sorry... stock exhaust.

I know factory pro has kits for no airbox (using stand alone pods or filter) applications. they come with bigger main jets.

[Hokie11]

ah so i finally found what you meant on the fp site, part #CRB-K13-3.0 is for 88-07 250s with no airbox

but then i saw http://www.perthstreetbikes.com/foru...et-mods-52595/

which lists same part for 08s. are the jet kits compatible with 08/09s even though fp site says up to 07?

hella expensive on the fp site... do you guys know any other sites that stock the appropriate jet kit?

[kkim]

http://www.factorypro.com/Prod_Pages/prodk04.html

[Hokie11]

ok i feel dumb. i think fp needs to redesign their website though, i feel like it was done in microsoft frontpage of a high schooler.

thanks kelly!

[Momaru]

Originally Posted by kkim

take plug readings to figure out if you need to go up or down from there

Noob time for me. Plug readings are? The method for figuring out 'up, down or stay' that I've been told/seen is take the bike for a ride and try to decide if it's pulling harder or not mod-range. Is the 'plug reading' more accurate/easier?

[kkim]

plug reading to select the correct main is the most accurate. If done correctly, it gives you a snapshot of what temps are being produced in the combustion chamber.

too lean = white
just right = light tan
too rich= black/sooty

there's a lot more that can be told from reading your plug conditions, but for picking the right main jet this is basically what you need to know.


http://www.superstreetonline.com/tec.../photo_03.html

http://dirtbike.off-road.com/dirtbik....jsp?id=332655

[Momaru]

Ah ha. Thanks. That'll make things much easier for me when I pull the box and rejet in the upcoming weeks. Was dreading trying to remember 'is it pulling harder now or before?' for every jet in the set.

[kkim]

depending on what your intake/exhaust setup will finally be, you can check the jetting database for good starting places on how to initially set your jetting. after that, it's fine tuning for your location and particular bike.

you can start all over w/ plug checks, but why do that when people before you have done the work, which is sorta the reason for the database.

I mentioned plug checks for Hokie cause I have not seen a stock exhaust used with a pulled airbox configuration before and was giving him a best guess on a main to start out with.

[Momaru]

Ahh so plug checks are more of a 'rough tune' while fine tuning is just judging how well the buke runs for you on a given setting? Or Plug checks work all the way thru to fine tuned (but I suspect the gradations would be a bit harder to differentiate). Haven't done fine tuning of much of anything before.

[kkim]

plug checks can be used to fine tune, but you really need to know how to read the plugs. For basic, ballpark main jet settings, what I listed on plug colors are close enough.

Plug readings are really useful in 2 stroke applications, where being off by just a little bit seems to make a life or death difference to an engine.

on 4 strokes, like our bikes, I see a lot more tolerance to bad jetting before the engine is destroyed. That's why I recommended using the jetting database as a start. You might be happy with those settings and you could live with it and be perfectly happy.

again, be mindful that jetting can vary, so no one setting is "right", but needs to be fine tuned to gain the maximum. I prefer my jetting be a bit on the rich side than lean.

For me, rejetting has produced a little bit more top end HP, but the biggest gain was in the power gained overall to flatten out the power curve throughout the entire rev range of the bike. While before the bike was anemic on the lower end, had a nice midrange pull and died off towards the top end, the rejetted bike now pulls evenly from low rpm to redline.

[Nevrfastenuf]

Originally Posted by kkim

if you yank the airbox, I don't now anyone who has done so that is still using the stock exhaust. You would need to change the main jets. (costs about $5 each) I'd suggest using 110 Keihins to start and take plug readings to figure out if you need to go up or down from there.

Last weekend I removed my airbox and replaced it with some UNI pod filters (I like Vex's K&N filter the best and may order one some day but the main warehouse for RockyMountainATV.com is just a couple miles from my house and they had the UNI pods and Keihin main jets in stock so I went that route for now).

I have the stock exhaust still and I found the Keihin 100 main jet with 4 washers under the stock needles and the pilot screws turned 2.5 turns out worked pretty good for me. The plug color after partial and full throttle runs looks pretty good and it pulls noticeably harder than stock from idle to redline. It also feels a little smoother when transitioning from coasting to partial throttle acceleration. Getting the airbox out was a pain but when you start tuning the carbs it makes it worth every second of it to have all that open space in there! The stock exhaust sounds noticeably different without the airbox in there as well.

I am at 4700 feet above sea level and I may be a little closer to being lean than rich in a few spots at the moment so please take that into consideration when looking at these numbers. I think the 105 main would be better for me (I haven't had time to try it yet though) so Kelly's suggestion of a 110 would be a great place to start for anyone at a lower elevation. I hope to have my new exhaust on sometime in the next week and I will post my new settings after I get that installed.

[Momaru]

In the OP I see Vex mentions needing/remembering late that the gear box needed a breather when pulling the box. Anyone happen to save the specs for the size of that tube (or other important measurements) so I can get a breather ahead of time? Likely gonna end up doing this in noche or another friend's garage, so the fewer trips I have to make to the auto parts store the better. Thanks!

[noche_caliente]

well, at least the worst case is advanced about 2 mins away, or autozone at about 5

[Momaru]

For reference, to connect to the end of the gearbox breather tube, it's 10mm inner diameter, 15mm outer. To connect directly to the gearbox nipple and bypass that looping tube, the OD is 22mm. I wound up just getting a double-male vacuum tube connector to bridge between the 10mm and my 12mm inner diameter cheapie breather.

[Betlog]

Now that the air filter is exposed, wouldn't this be dangerous when it gets wet (i.e. rain) and lead to damage to the bike?

[Betlog]

^^ Hydrolock... that's the word I was looking for.

[kkim]

for the bike to hydrolock, you would need the water level at the height of the air filter which would put it about up to the seat. if you're in that deep water, you've got other problems besides worrying about your bike being hydrolocked.

[Betlog]

Originally Posted by kkim

for the bike to hydrolock, you would need the water level at the height of the air filter which would put it about up to the seat. if you're in that deep water, you've got other problems besides worrying about your bike being hydrolocked.

Pardon my n00biness, but wouldn't getting the filter wet from rain (or washing the bike) do something similar?

[kkim]

hydrolock occurs when the cylinders fill up with water and the pistons can't compress the liquid filled cylinders... usually when the engine is running.

water on your filter from rain or washing is not going to do that. in fact, some people use a water spray/fogging to clean the carbon out of their engines. I wouldn't do that, but not because of any concern of hydrolocking the engine.

[Betlog]

Originally Posted by kkim

hydrolock occurs when the cylinders fill up with water and the pistons can't compress the liquid filled cylinders... usually when the engine is running.

water on your filter from rain or washing is not going to do that. in fact, some people use a water spray/fogging to clean the carbon out of their engines. I wouldn't do that, but not because of any concern of hydrolocking the engine.

Cool. Thanks for the explanation.

[sixer]

I live in a sandy dessert area- sand every where-
Could i do this ?

how often do you change it? seems like a pita to change...

[kkim]

how often do you have to change what?

[Momaru]

Assuming you're talking about replacing the air filter pod once the airbox is gone, IIRC, the K&N filters are guaranteed for either 100,000 or 1,000,000 miles, provided you clean them out every so often (think it's 50,000 miles). I'll check the product stuff when I get home if you'd like. Essentially you shouldn't need to change it.

Since I imagine the air filter was designed to remove the exact particulate that you've got a lot of, amongst others, I don't see what would be an issue. I imagine it'd be fine in sandy environments provided you made sure the seals to the carb were tight (keep from sucking unfiltered air in) and kept an eye on how clogged it gets (which is easy since you can see it even with the black leg protector plates on the bike). However I'm neither an expert nor a California resident.

That said, very easy to remove/change at all if you decide to replace or clean it. Especially when you compare how much of a hassle it is to get that airbox out...

[backinthesaddleagain]

Watch offshore powerboat racing, those things suck in some h20

[ninja250]

Originally Posted by sixer

I live in a sandy dessert area- sand every where-
Could i do this ?

how often do you change it? seems like a pita to change...

I think you just "hose them off" with water and then blow dry with an air compressor. They also have K&N air filter recharge kits, but not sure if it works with that filter or not.

Some dirt bikes use an unrestrictive foam element over their air intake filter. I'd imagine you could find one at a dirt shop if it's really bad.

I do notice my bike gets pretty dusty very quick out here
then again I've been riding it in dirt too. haha

[wyckedflesh]

Has anyone, aside from me, thought of cutting the airbox with a dremel to have the stability of the framework and use the K&N single pod connected much the way KKim has his?

Sixer, there are "Outerwears" made for sandy/desert off road vehicles that go over the K&N filter to help filter even more and makes for an easy pull off and clean element to give your K&N more life. One of the items I am looking for here in the High Desert when I get down to the point I make this mod. rejet and add an exhaust.

[Ken08Ninja]

Here's a link to the water repellent Outerwears prefilter for the K&N R-0990 filter.
http://www.outerwears.net/proddetail.asp?prod=4128


They also have a regular one that is not water repellent.
http://www.outerwears.net/proddetail.asp?prod=756

[Momaru]

Originally Posted by kkim

I also used the rubber runner pieces from the stock airbox and used them to lengthen the runners from the filter to the carbs.

Anyone measure the length of the runners that are inside the air filter once one has done this? Curious if it's a close fit to the back wall of the K&N (potentially restricting airflow) or ir if there's more clearance than I think. I'm set up this way, but it's about 13F outside now and I don't have a garage, so it's a little cold to strip the bike down to satisfy curiosity.

[wayanlam]

Originally Posted by VeX

Ok so it begins:
Ohh shiny

what were to happen if i just plugged that hose/hole up? i cant get a small small air filter for this hose.



in the meantime i just improvised and created a filter with quick dry foam and some fabric...



here is another lil .gif i just made up from todays K&N installation~

took quite a while to get it all down and back together, lol

http://img.photobucket.com/albums/v8...rboxdelete.gif
thats a link to a higher res .gif

W.

[Banzai]

You'll need something, as that's the crank case breather.

[kkim]

Yes, you can't block off that hole. You can blow your crankcase seals if it's not allowed to breathe. I use a cheap gasoline filter that fits the hose.

[wayanlam]

okay, all clear, i wont block the crank breather! ill see if i can find a fuel filter to do the job. my temporary sponge and cloth filter looks a little out of place in my bike, ha ha

so this morning i finally had the chance to ride the bike, i wasn't able to push her to red line cos it was rush hour, and the roads were chockablock. however i noticed an unfamiliar sound when im in the lower Rev range. like when i start accelerating from a slow speed (10~15mph) in 2nd gear, i get a really throaty gurgling sound from like 3k~6k rpm, then once im into the mid/high rpm range it goes away.

the sound is definitely coming in from the carbs (right under the seat). however i don't hear this when i am just revving the bike when its parked, so its something that only happens when there is a force on the back wheel.

---------------------------------

i have noticed another small issue when installing the K&N filter, and its that its resting on the metal/rubber ring that used to hold one corner of the OEM filter (where Kelly put the pipe through to the right of the filter in his picture)



i am wondering if i should do the same mod as kelly with extending the runner pieces from the stock filter? Kelly, did you end up keeping that set up with the extended pipe? or did you plug the filter in directly to the carbs again?

thanks in advance

peace out~

[Momaru]

I think the sucking sound is your carbs drawing in much more air than they used to. Give it a LOT of throttle briefly while standing still (like from closed/idle to half or 3/4 open) and I think you'll hear the same sound you're describing. If that's it, it's the way your bike breathes now. I'll try to get a recording of mine in the next day or so for comparison.

For what it's worth, I left my stock runners on, but ran a big zip tie around the filter between the runners & attached it to the zip tie holding up the carb. But whether you use the runners or not MAKE SURE YOU TIGHTEN YOUR CLAMPS! I didn't tighten mine enough the first time around and the carb end of one runner fell off; sucked in road crud for an unknown period. Got to spend about a week & a half cleaning dust & gravel out of my carbs & engine because of that.

[kkim]

I still have the extenders from the stock airbox installed as in that picture. bike runs fine.

[wayanlam]

Originally Posted by kkim

I still have the extenders from the stock airbox installed as in that picture. bike runs fine.

alright! im gonna do that too then

besides the filter being in contact with the metal ring, its also touching on the fuel tank tap, i don't like the idea of these parts all chafing together, im sure it will damage the metal wire mesh of the K&N filter in a very short time...

so, i just went on another ride, and the gurgling sound that i was talking about it most audible between 5k and 6k rpm, when im opening the throttle.

i can hear a similar sound when i WOT while the bike is parked, but the sound only lasts for a split second (coming out of the lower into the mid RPM as well), but its there!

i guess im taking my bike apart again when i get home! yippie, lol...

the bike pulls decently all the way up to redline, but i am not sure if its better or worse than before i replaced the air filter and re-jetted... i think im gonna pass by the dyno place next week end and have them run it again to compare it with the old dyno run. i mean i would expect an increase, be a little dissapointed if it didnt change, and definitely be annoyed if the dyno got worse, ha ha... well it just means ill have to figure out what needs fine tuning, get the right jets, and tune her some more.

cheers all

[wayanlam]

Originally Posted by kkim

TJ,

I also used the rubber runner pieces from the stock airbox and used them to lengthen the runners from the filter to the carbs. I like how solid the runners mount to the carbs and how the other end of the runner slides easily into the r0990 filter's openings. Everything clamps up quite nicely.

i just took the stock runners out, and am not sure how you fixed them to the K&N's... did you use a pipe inbetween? as per your coment and image, it looks like yuo just slid the stock piece into the K&N filter. but im not sure i can do that, cos there are like 4 ribs on the outside of the stock runners, which would cause air to slip by no?

or did you do some mild operations to them to remove these ribs?

there they are circled in red~

looking forward to your reply master!