<div class="FTQUOTE"><begin quote>Originally posted by: icanzu

With a modded engine I still don't think that the little bit of power difference is worth the cost of the potential motor damage. I'm running a 440 BB with cam and carb mods +++. Maybe that's why I barely notice any difference in power between the NoToil and the K&N. If you're in dust or sand I can't see going K&N....unless you're makin' the big bucks and don't mind the risk of suckin' dirt. Oil or no oil, hold a clean K&N up to the light and look through the inside. Now do the same with foam.... I know a team that races go-carts and dirt bikes and they all use NoToil dual stage filters and still win races.....Speaking of which, why don't dirt bikes use K&Ns?</end quote></div>

Well, I don't know if dirt bike use them or not. If they don't then I would venture a guess and say that the dirt plugs the KN to the point that the flow is reduced to that of a foam anyway... So, why not run a foam to start with and save the engine? But who knows for sure why people do what they do. Maybe they get free filters from one company and KN wont give them any. I dont know.

I think there are more variables than just the flow rate of the airfilter anyway. The carb selection has a lot to do with flow as does the porting of the head and valve size. Might as well chuck the cam into the mix too. Does it have enough lift to take advantage of the flow? Usually, the more lift your cam has, the more flow you need. And you gain flow by porting, bigger carbs, and less restrictive filters. To what degree you will notice an air filter change has to do with the flow requirements of the engine. If the engine can't utilize the extra flow, then its a mute point.

You have a BB 440 with cam and carb mods... What are carb mods? Did you bore the carb out? Get a bigger carb? Or just jet the carb you have? Is the carb a CV carb? Did you do any porting? Do you have flow numbers to suggest the porting actually made any difference? Did the new cam have significantly more lift than the old cam? There are just too many variables to say why one engine has big gains from extra flow and the next guy says he didn't notice a thing. I suppose its just a $40 gamble.

One thing that comes to mind while thinking all this out is that if you aren't ready to toss your airbox lid and rejet your carb, then don't get a KN. The airbox will probably hold back any gains you thought you might get with a KN.

 

Not a bad read for general knowledge anyway http://www.knfilters.com/faq.htm

 

i just won a stage 1 and 2 jet kit waiting for it to arrive iam just trying to give my atv a little more peep not rebuild it from ground up not for atleast a couple years when i get bored with it.

 

The 2007 Z400 comes with a Mikuni BSR36 carb according to Suzuki.com. I googled that carb and it is indeed a CV carb. That means it belongs in the garbage, lol. The advantage to a CV type carb is smooth throttle resonse and you don't have to rejet when you change altitude. The disadvantage is lack of crisp throttle response and they are notoriously finiky about changes you make to the filter and airbox and anything else to do with airflow. See,,, when you press the throttle, you actually open a butterfly valve that lets engine vacuum suck the slide up by means of a diaphragm. So, its not YOU giving it gas, its the engine vacuum giving it gas. And that means there is a delay between when you punch the gas and when the quad actually starts to go. IMO, that sux!!!! Furthermore, if you stick a KN filter on, there will be less vacuum to open the throttle and it will cause you headache after headache trying to get it to run right. It will starve for gas and you'll end up putting 10x bigger jets in and still not getting it quite right and pulling all your hair out in frustration. [img]i/expressions/face-icon-small-mad.gif[/img] Either put the stock filter back on or an equal foam filter and leave it alone or get a new non-cv carb with a KN filter.

I think the manufacturers deliberately "dumb down" large displacement engines so people wont get hurt. Large cc's sell quads, that = more $$$. But a 400 really should be insanely poweful if the manufacturers didn't restrict them the way they do. Really,,,, a CV carb on a sport quad??? Maybe if its grandma's first quad. But anybody serious about having fun deserves to be able to give it gas when they press to go button. [img]i/expressions/face-icon-small-tongue.gif[/img]

My 230 quadsport has a 67mm stroke and I can rev to the moon with that thing. The Z400 has a 62.5mm stroke and for some reason it don't want to rev out. A 90x62.5 bore n stroke is intrinsically designed to rev out by virtue of the large bore/stroke ratio. My 68x67 is a bit over 1:1 and not really a high revving combo w/o major engine beefing. So, what's the problem? The darn CV crap carb is one. My bud's warrior has the same problem. He should be able to run off n leave me wondering where in that big cloud of dust he went.... But he can't. If you want pep, change carbs and you'll be happy. [img]i/expressions/face-icon-small-smile.gif[/img]

 

i was thinking about that already thanks for the info[img]i/expressions/face-icon-small-cool.gif[/img]
oh yeah edelbrock would be a good eone to go with

 

Yeah, hard to go wrong with edelbrock, but I hear they like lots of $$$$ for one of those. [img]i/expressions/face-icon-small-wink.gif[/img] Mikuni isnt a bad alternative, but they dont come with the edlebrock sticker, lol.

 

now how to figure out which one to go with i checked it out i was thinking about the 38mm MIKUNI TM Flat slide smoothbore carburetor which is only a 145$$ which is a lot cheaper any sugestions or the 36mm MIKUNI TM Flat slide smoothbore pumper carburetor 13-5070
with accelerator pump for 4-stroke use
which is about 300$$ actully there is quite a few optoins on pro cycle
omg so many differnt ones and dont exacty know what differnce is or which would help the most[img]i/expressions/face-icon-small-confused.gif[/img]

 

Well, the 38 will flow more air at higher rpms than the 36, and the flat slide gives good response at low rpms,,, so it boils down to whether you need a pump,,, and that boils down to how fast you want to be able to stab the throttle and have it go instead of die. I have a 28mm flatslide with no pump on mine and I can stab it pretty fast with no problem, but my engine is a lot smaller too, so that's a tough one. I guess you can always buy the pump later. I think I remember reading at sudco all the flatslides are upgradeable to pumps if you want (except maybe the 28mm).

Either way, you'll still be able to take off faster with a no-pump flatslide than the CV carb you have now. But a pumper might be faster still.

Another thing I just thought about since you have a new quad is rev limiters.... Do you know how high you can rev before it kicks in? That may be something you should check into as well. Since the whole goal of a bigger carb is to be able to rev out more n all.

 

i beleive it revs out at 9100 with limiter i know with some of these cdi boxes you can get another 2000

 

ok, 9100 is enough to need a bigger carb. Need to find some guys that have actually changed carbs and see what they think. I dont even own a 400, lol. The pump no-pump is a good question. I don't think you can go too big with the carb... After all, I know a couple guys that have 32mm on 250's. Seems like you could go well into the 40's and still not be too big. 38 seems pretty close.... Its bigger than stock, but small enough to retain all the lowend grunt you may like. Usually the bigger the carb the less lowend you get.