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Adding power? Ehh, probably not. But, aftermarket ones are more compact, easier to clean and cheaper. I prefer Twin Air.

I agree. I don't think the brand of air filter is worth any power, but some of the aftermarket stuff is better quality, cheaper, etc.

When and how you prepare them is worth some power for sure. About 10 or 15 years ago one of the magazines (MXA?) did a bunch of dyno testing with a CR125R. They found that a freshly oiled filter looses 1 or 2 horsepower over filters they oiled the night before. Aparently it takes some time for the filter-oil to "wet-out" and for the application solvents to evaporate away. As a rule, I keep at least two pre-oiled filters in zip-loc freezer bags ready to go. If you do that, squeeze out some of the air so they don't burst when you leave them in your truck cab during the heat of the day.

I would never run a paper or gauze filter like a K&N in a dirt bike. They're ok in a car, but you really need the oil-bath-foam filter to deal with the dust and fine particulates we have in motocross, off-road and the desert.

I like the Uni-Filter and Twin-Air brands. I run Uni in all of my YZs because they are two pieces, that makes them very easy to clean.

OEM Yamaha filters seem to degrade quickly... as in they disintegrate.

I bought a Moose brand filter and I won't run it. They don't fit the Yamaha air boxes correctly and they're a pain in the ass to install due to the rubber gasket. That rubber is closer to hard plastic and it's too small for the plastic stud. A close friend had exactly the same issue on his YZ250F with the same Moose filter.

Other Moose brand stuff is great and perhaps their filters are good for other bikes... just not the YZ or YZ-F.

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Wow, this is timely.... I'm in the process now of selecting which air filter would be a better replacement for my OEM.

Uni or Twin-Air? What's the difference between them?

Thanks!

I believe them to be of equal quality, and they both seem to filter very well without loosing any power.

I prefer the Uni-Filter brand only because their filters seperate into two pieces for cleaning.

The outside layer, the low density foam seperates from the inside layer of high density foam.

The Yamaha GYTR brand filters are re-packaged Uni-filters.

All of them seem to last longer than the stock filters.

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I've seen a No-Toil Display that had a dyno chart on it for No-Toil vs stock. There was barely any difference, but the No-Toil made a little more power after peak.

But the Filter doesn't fit the cage very well... I like the foam and the glue, it's lasted almost 2 years now, but the fit is really bad.

The Twinair fits great and seems to be lasting alright, but there's less difference between the foam densities, and it seems to take less oil than the No-Toil or stock did. I didn't realize the Uni comes apart though. My next filters will be Uni for sure.

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I'll admit on the front here that I am a huge K&N fan. I have been using them on dirt bikes since 1971 (yea, I'm an old guy but used to be an 'A' level enduro rider - just trying to establish a little credibility here). K&N's get a bad rap because when run in fine dust the oil is absorbed and they lose the ability to filter (no foam or gause filter will work without the oil!). In these conditions you should re-oil them between rides by just applying oil to the top of the filter and letting the oil wick down through the rest of the filter body; they will continue to filter as long as the filter element is oiled. Those who say otherwise are just plain wrong!!! Keep them oiled and you can go a really long time between cleaning. Their real advantage is in cross contry riding - if the bike sucks water thru the air filter only water passes; do this with a foam filter and you'll see that 'muddy' water passes. Try it for yourself - run water from a fauset gently over a dirty foam filter and see the mud that passes thru to the inside. Then do the same to a K&N - you get the water but not the mud. K&N claims more HP but I have never seen a dyno run to prove it; I feel that the HP levels are so close that no mere mortal can feel the difference.

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I'll admit on the front here that I am a huge K&N fan. I have been using them on dirt bikes since 1971 (yea, I'm an old guy but used to be an 'A' level enduro rider - just trying to establish a little credibility here). K&N's get a bad rap because when run in fine dust the oil is absorbed and they lose the ability to filter (no foam or gause filter will work without the oil!). In these conditions you should re-oil them between rides by just applying oil to the top of the filter and letting the oil wick down through the rest of the filter body; they will continue to filter as long as the filter element is oiled. Those who say otherwise are just plain wrong!!! Keep them oiled and you can go a really long time between cleaning. Their real advantage is in cross contry riding - if the bike sucks water thru the air filter only water passes; do this with a foam filter and you'll see that 'muddy' water passes. Try it for yourself - run water from a fauset gently over a dirty foam filter and see the mud that passes thru to the inside. Then do the same to a K&N - you get the water but not the mud. K&N claims more HP but I have never seen a dyno run to prove it; I feel that the HP levels are so close that no mere mortal can feel the difference.

K&N filters hold a smaller volume of oil and have less surface area than the equivalent OEM foam filter. That's why you have to re-oil them so often.

If you don't wash and oil your filter at least once between each ride/day, you're probably not getting the best performance or protection out of any type of filter, especially the K&N types.

If I'm at a practice day and it's dusty, I'll generally use two or more filters in the bike. If it's a race day, they ARE getting checked and/or swapped between motos.

The K&N let's more of that fine dirt pass through, that's why it doesn't show up in your water test.

I live in one of the places that gets the highest rainfall on the planet... I don't pour water into my air-box during a motocross race... Use some duct tape to divert the water away from your filter... that's a bike prep issue, not a concern you should use to choose a filter.

Name one factory team that uses K&N type filters in outdoor motocross or desert racing.

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I've seen a No-Toil Display that had a dyno chart on it for No-Toil vs stock. There was barely any difference, but the No-Toil made a little more power after peak.

But the Filter doesn't fit the cage very well... I like the foam and the glue, it's lasted almost 2 years now, but the fit is really bad.

The Twinair fits great and seems to be lasting alright, but there's less difference between the foam densities, and it seems to take less oil than the No-Toil or stock did. I didn't realize the Uni comes apart though. My next filters will be Uni for sure.

How in the world did you get the no-toil to last 2yrs?

I'm lucky to get 8 months before seams split/unglue. Used both the red and green stuff.

Would like to go back to regular stuff, but man, I love cleaning and ease of use with the No-Toil.

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How in the world did you get the no-toil to last 2yrs?

I'm lucky to get 8 months before seams split/unglue. Used both the red and green stuff.

Would like to go back to regular stuff, but man, I love cleaning and ease of use with the No-Toil.

I don't know, I have 2 filters, and it's in every other week I guess. It's held up way better than stock, but it sticks like a bastard if you don't use their runny grease on the rim. I could definitely see it tearing there.

I guess I'm pretty gentle when I wash it too, if you use enough of their soapy stuff it pretty much scrubs itself. The workmanship is nowhere near the quality of twinair, but I like how much surface area it has. It really seems to catch more dirt that the twinair. When I'm washing them together I swear more comes out of the No-Toil

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K&N's do not let more fine dust pass thru 'if' oil is added when they start to dry out. The dust in parts of the Southeast is like talcum powder and will not pass thru. I have run 100 mile enduros in dusty conditions without showing any ring wear. And yes, I have done engine teardowns with measurements showing no wear. I agree that power will be lost when they start to clog because this causes a rich condition. Factory teams do not care about the cost of ownership; they are not paying the bills. I will say this though, a foam filter is a lot easier to service than a K&N which are a pain to get out/in on a YZ250/YZ450f.

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I have a Uni and a twin air. I alternate them for cleaning purposes and cannot tell a difference in power or filtering ability. Both do a fine job and seal real well against the air box.

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OK, here is what really bothers me about this discussion. We have no way to quantify our results. Strangly enough, we both may be right for our riding conditions. Even a 'home' test of pouring water thru a dirty filter might have different results (hot water???). All that being said, I still like the K&N for single track conditions.

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Has anybody ran a LoudMouth system? I know there are other systems similar to this, just this is one I've seen quite a few people running.

http://www.loudmouthmx.com/ It takes away the mounting from the inside which "restricts" (doesn't restrict much at all, but I'm sure some) I was thinking about it, let me know if you have tried it!

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I'll admit on the front here that I am a huge K&N fan. I have been using them on dirt bikes since 1971 (yea, I'm an old guy but used to be an 'A' level enduro rider - just trying to establish a little credibility here). K&N's get a bad rap because when run in fine dust the oil is absorbed and they lose the ability to filter (no foam or gause filter will work without the oil!). In these conditions you should re-oil them between rides by just applying oil to the top of the filter and letting the oil wick down through the rest of the filter body; they will continue to filter as long as the filter element is oiled. Those who say otherwise are just plain wrong!!! Keep them oiled and you can go a really long time between cleaning. Their real advantage is in cross contry riding - if the bike sucks water thru the air filter only water passes; do this with a foam filter and you'll see that 'muddy' water passes. Try it for yourself - run water from a fauset gently over a dirty foam filter and see the mud that passes thru to the inside. Then do the same to a K&N - you get the water but not the mud. K&N claims more HP but I have never seen a dyno run to prove it; I feel that the HP levels are so close that no mere mortal can feel the difference.

Good day Ken. i've used a K&N on my Isuzu Dmax 3.0-litre diesel pickup. In places where it's dusty, such like Metro Manila, i find it quite heavy on the maintenance. I had to always clean and then oil it. Bought the oil from the one of the K&N dealers in the city. When the K&N is newly-cleaned, a noticeable seat of pants gain can be felt especially when the diesel turbo starts to spool, around 1800 rpm up. But when it's dirty as described, it just felt the same as the stock OEM filter in terms of performance. I tested a Hurricane air filter from a friend of mine, and i find it quite better than the K&N and the OEM. But i never bought one though.

I removed the K&N once i got my 1st-stage diesel EFi tuning kit, RaceChip Pro from Germany. For me, the K&N is already irrelevant as the power gains from the chip is way way higher, consistent, and no incessant cleaning and oil bathing is involve. I'm using only OEM air filter at the moment.

I may have to say this, judging on the performance of the K&N (that i have used which is now kept on standby awaiting to be sold), especially in high-dust environment, i will never use one for my YZ250. Might take the Uni filter at this stage....

Edited by joshua_inigo

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I bought a Loudmouth for my crf450 and I can tell you that it was a MASSIVE power increase! The bike would wheelie uncrontrollably in EVERY gear!! Okay...I didn't actually notice a difference, but my filter was easier to remove/install, so that was cool.

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Ok we have determined that uni/twin-air are top notch in longevity compared to stock,no diff in performance. I use k&n filter spray oil for thier paper filter,im thinking it might be a bit thick,what type of oil do you find that works best.

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I have used the PJ1 (red) and the Bel-Ray (blue) oils on my filters.

Both seem to apply easy enough, and both seem to tack up and filter really well. If they were on the shelf next to eachother for the same price, I would grab the Bel-Ray simply because it is dyed blue... That contrasts well with a red Uni-Filter so I can tell how much oil has soaked and if I've missed a spot. The PJ1 oil is red and it's really hard to see on a red filter.

Both PJ1 and Bel-Ray leak like crazy when you spray them. I've bought brand new cans of both and had them leak around the button on the very first spray. So now I have sticky filter oil all over my right hand and a sticky air filter in the left. I don't like either brand of spray-oil for that reason.

Pouring some oil in a zip-loc freezer bag with the filter will be my next move. All my filters wind up in those bags when they're done, so it's no big deal.

I bought a couple bottles of filter oil that you pour on the filter (I think it's Bel-Ray) but haven't started using them yet. I still have a few spray cans of PJ1 in the tool box.

If memory serves, the Maxima spray doesn't leak. My local shops don't carry it though and it's been since 2009 that I've used it.

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K&N's do not let more fine dust pass thru 'if' oil is added when they start to dry out. The dust in parts of the Southeast is like talcum powder and will not pass thru. I have run 100 mile enduros in dusty conditions without showing any ring wear. And yes, I have done engine teardowns with measurements showing no wear. I agree that power will be lost when they start to clog because this causes a rich condition. Factory teams do not care about the cost of ownership; they are not paying the bills. I will say this though, a foam filter is a lot easier to service than a K&N which are a pain to get out/in on a YZ250/YZ450f.

It's generally accepted in the industrial world that K&N filters cannot handle any significant amount of dust and do not hold up to the long change intervals seen in industrial applications. While they may not pass dust, they simply plug up. The paper Donaldson filters with cetrifugal dust seperators are preferred. There is a new style of filter which is coming into common use. It looks like a honey comb when you look through it. I think they claim 300x the surface area of a pleated filter. They're expensive at $350 per filter vs. $50 per for a pleated filter but their life is significantly longer.

Now, in the desert you won't come across that puddle that swallows your bike whole. Ride your airbox underwater and you will be thankful of your oiled foam filter. As long as the complete element doesn't go under water, chances are your bike will still be running once you get to the other side of the puddle.

And for what brand to replace your OEM filter with? Well I'm new to the Yamaha world but when you put an aftermarket filter side by side with the OEM Honda filter for my 1987 CR 250 there was simply no comparison. The OEM filter was a 2-stage element with rubber gasket to hold it on the cage, it had a high density foam seat for the seal between the filter and the housing. It was sewn and glued together. It was expensive. It cost $35 and that was Service Honda's price. I'm getting ready to order an OEM filter for my 01 YZ to replace its current Twin Air, I'll let you know what I think.

Edited by 1987CR250R

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