Like most people who have added an aftermarket filter & exhaust, & took off the airbox lid, I have been through jetting hell & back only to find that a slight turbulence problem is created by this setup in the 1/4-1/2 throttle position. I have rejetted so much that I had to replace some carb parts already so I know how to jet & don't really want anymore advice about turning the fuel screw a little this way or that.

What I am looking for is anyone who purchased one of the aftermarket airboxes that uses the 250R air filter in which one air filter is funneled down into two intake boots & supposedly there is a an inch or so of space between the filter & carb boots. I thought I read a post that said this type of air box helped to reduce the turbulence problem? I know I've heard that the FCR carbs helped but I am not ready to spend that kind of money on them just yet. I am still looking to resolve the trouble with air/fuel intake changes.

 

I have the same mod done and no problem with it, im using the stock air screw settings. Some times you have to just fall a touch on the rich side and pay for a sparkplug every few weeks. I am about to install a proflow kit, I dont know what it does for turbulence. On a side note, did you move the needle jet clip position? maybe you moved it the wrong direction? Once upon a time I had a terrible problem with 1/2 to 1/4 throttle and it turned out that I was way to lean because dyno jet jets are smaller than mikuni. I was running a 146 dyno jet which is really like a 140 mikuni so the 146 I was running was actually smaller than the stock 145, when that happened it ran fine on top end, ran fine in mid range but sounded like a two stroke at 1/4 to 1/2 throttle.

 

I've been looking into the aftermarket airboxes too. There biggest selling point seems to be the reduction of turbulance.
I Dynoed my Raptor with & without the lid & there was a lot of turbulance with the lid off.

You could see on the dyno graph, it looked like a roller coaster. All the pulls with the lid on were smooth.

Turbulance with CV carbs can't be good!!

 

Thanks Jakal but its not really that confusing to me if you know how much jetting I have attempted. I have tried probably over 100 different combinations with Dyno jets and with stock Mikuni jets. I even tried mixing the two types which made things worse. I guess I should have stated the way I am jetted currently so you'll know how far I have been to jetting hell & back. Oh ya, I've moved the clip up/down- all around, I tried jetting the mains from 140-145 all the way up to 170-175, pilot jets ranging from 22.5 to 30.5, I've worn the fuel screws out- got new ones on order, I've worn out the slides- replaced them, worn out the clips, relaced them, tried drilling out the slide air hole a little, tried changing the Mukuni needle diameter & length- got new ones on order. Trust me when I say I've tried everything. I totally agree that there are some sweet spots that enable you to get real close but any weather temp/humidity changes throws off the balance.

My current settings are using Mikuni jets only: 22.5 pilot jets,
fuel screws = 3 in summer & 3.5 in winter, clips = 4 in summer & 5 in winter(yes I tried staggering them too), mains = 165-170 in summer & 170-175 in winter.

With this setup, she friggin rips from 1/2 - full throttle but suffers a turbulence problem around 1/4 - 1/2 throttle. I just read a ton of posts from back in early 2001 when a lot of people were talking about this & seems like even the experts agree that the CV carbs are difficult to jet when you remove the airbox lid.

I have read quite a bit on jetting & the one parameter that impacts this throttle range the most is the slide cutaway, the problem is, nobody makes different ones(leaner or richer) so no luck there either. I wish somebody would invest a few bucks in making different sized slides & then we all could get our jetting real close for a lot less money & aggrevation!!!!

Moose, I agree with you. You may notice that Trinity & Edelbrock make some type of induction kit in which they utilize a chamber to create space between the airfilter & the intake boots, perhaps this puts back some of the vacuum & air velocity that is lost when you remove the lid at low throttle positions? That is why I am curious if using one of these aftermarket airboxes that has a space between the filter & the intake boots helps the situation or not.

 

Hmm, you've been battleing this problem for a long time. Sounds like the only thing left is to move to a dryer more stable climate. [img]i/expressions/face-icon-small-wink.gif[/img] Hope you get it handled soon.

 

Chimmer, I would have to say yes the aluminum boxes do help with the turbulence, because there is so much more space around the filter. I haven't used one but I have had a couple good conversations about them. Talk to Swytak I know he has one and he is always helpful to me.

I have a question for you and MOOSE, do either of you ride in water? If your not running a lid I doubt you are. So why not go with the clamp-ons? I hav said this time and time again, I gained as much switching from a Pro Flo foam to the clamp-ons as I did with the pipe and filter in the first place.

 

What if you put filler in the inside your air box to control how the air flows and get rid of rough edges. Let your creative mind flow with some bondo then if it dosent work get the new one lol. Atleast you could say something on your bike was truly custom. Edited out the part about the 148 main jet, sorry bout that, got warrior stuck in my head right now (thought I was in BT warrior forum lol)

 

Ward, ya man, run through plenty of water here in PA, mostly puddles that we try to pull wheelies over but some are too big/long or too many in a row to avoid & the bike gets real wet/muddy sometimes! I use an outerwear cover for the airbox.

Jackal, I like your idea about customizing, as a matter of fact my airbox is already butchered so much that I had to use some JB Weld to keep her together. I was thinking about replacing the existing airbox with some 5-6" diameter PVC & making a new intake connection as well. That way the filter is surrounded by smooth walls & if I extend it to the battery compartment it will be protected from the elements as well. I would still need an outerwears slip on but no big deal. I'll keep trying & thinking, not going to be doing much riding this time of year anyway, its getting cold & everybody's hunting....[img]i/expressions/face-icon-small-sad.gif[/img]

 

Chimmer have you tried the GYT-R needles? I just installed their jet kit and bottom end and lower throttle settings are exelent so far. I think it's still a little lean WOT 160/165. Based on some of your previous posts I'm going with 167.5/172.5 mains. I'm hoping the low end gremlin does'nt show up when I get the top end jetted correctly. Thanks for sharing the knowledge gained through your jetting hell.[img]i/expressions/face-icon-small-smile.gif[/img]

 

Yeah, if you make the air box out of round PVC and vent the top, then since its long you could put some sort of fan in there too on the end of it since it would be right by your battery lol. Wouldnt that be sweet, when ur draggin take off the end cap, cover up the top vents, cut ur fan on and BOOHYAAH, baby turbo. then when your not draggin put an end cap on that end and take off the plate covering the top of the pipe. Then you start manafacture them and make money, then i get pissed at you stealing my idea and you have to buy me a new quad [img]i/expressions/face-icon-small-tongue.gif[/img]