Just K&N - need rejetting?

[tri650]

I have read a number of threads on re-jetting with aftermarket filters and exhausts. My parts bike had a brand new K&N on it that I want to use on my running bike and wondering if I would need any type of re-jetting with the stock exhaust.

[scrapvalue]

I don't think you will need to re-jet for the K&N filter.
But for what little effort it takes to change the filter, just give it a try and see how it acts.
If acts funny, then tell us what it is doing and someone should be able to tell you what to do.
You can always but the stock filter back in.

[natemoen]

Very doubtful that you would need to rejet. As he said, not hard to change back and forth between filters.

[MrOzz]

When I had the K & N filter in the stock air box with the stock exhaust I did not have to rejet. I did have to adjust the Idle screws and re sync.

[bikerphil]

No re-jet should be needed. You could even drill the airbox out for even more air flow without any problems.

[ManagerMike]

K&N air filters are more about a successful marketing campaign then a superior air filtering technology.
Keep in mind that they developed their reputation in the off road racing circuits where a washable and re-useable filter had a financial advantage over a paper filter media which may need replacing after each race.
While they may may pass a bit more air than a paper filter when freshly cleaned and oiled, the added gain by a non-specialty built engine is, at best, negligable.
Whenever asked my professional opinion about the claimed performance gains of K&N filters, I've always rejoined with the challenge of temporarily removing the filter from the airbox altogether to see if the "reduced restriction in airflow" results in a noticable "performance gain" before plunking down $70. 00 on an air filter.
Funny, those people the accepted my callenge BEFORE spending the money on the K&N, invariably sensed no difference in power without a filter or with one.
However those that had already spent ten times the cash needed to buy a standard filter on a K&N, swear up and down that they FEEL more power.

Doesn't take a psych major to figure that phenomenon out. I am, however, bummed that I wasn't the one to come up with the idea first...

All that said, no. you don't need to worry about jetting to accomodate an air filter, no matter whose name it carries.

[cywelchjr]

The only thing I would say on it is that when your dealing with a filter that may not be around much longer that must be replaced vs one that is supposed to last the life of the machine and that you just clean and oil, it makes sense from THAT standpoint, the supposed power gain having nothing to do with it.

That said, I've seen dyno tests with the cold air kits increasing power on auto engines, but I figure it's the pulling cold air rather than engine compartment air that does it rather than the filter. My figuring on it is that if the filter actually does last as long as they are supposed to (and the one in my Camaro has so far) it will pay for itself over time in filter cost savings just from not having to buy filters, but then I don't use their expensive cleaning and oiling kits.

[Cobia]

No re-jetting necessary. As Bikerphil said and did, and I did as well, you can even drill the airbox for increased airflow with out any adjustments required.

[yamtom]

stock filter better?

I have been missing from this list for a few months, and have been reading up on other lists. In one of the yam venture lists, there was an article of a test on comparing stock paper vs most aftermarket filters with the primary concern being, how well the filters actually worked at removing dirt of all sizes from the intake stream. The info gleaned from that article was that, nothing but a stock paper filter works as well at removing dirt of all sizes. I will try to find that article and post a url for it so you all can read it for yourself, but it was very damning of all aftermarket foam filters in comparison to the stock paper filter. Gads, now I have to put the stock filters back on my bikes, how I hate that stock air box, and how!!!!!! Oh, to answer the mans question, my own cheapo pods didnt require changing jets, they make good power to 7000 rpm, I never go above that, and maybe you dont either.

An actual post with url, that for me didnt work, see below,

Q: K&N - Does more airflow come with a price?

OK, I am not claiming to have the answer to that question. This came up on a work break with a co-worker. He has a 65 Mustang and a Corvette from late 90's I guess. He does most his own work and seems like he has a clue... but who knows. He asked if I ever used K&N air filters and I said I had and have one in my bike now. I asked why?

He says he changed over to K&N's in his vette. After it was in a short time, he says he pulled it and looked at some screen that covers a air flow sensor of some sort. (he explained it, but I dunno) Anyway, he says the screen was partially clogged with very fine dust and stuff that had apparently gotten through the K&N. He said he never had that happen with a normal paper disposable filter. I asked if he was sure it was properly seated etc and he claims it was oiled and installed properly. We discussed it and then he later in the day sent me this link to a study apparently by ISO that shows the K&N does offer more air flow, but let more fine particals through than just about any other filter.

http://www.duramax-diesel.com/spicer/index.htm

Anyway, just offering this up as matter of discussion to see what you guys think? Besides... we haven't had a good debate on actual motorcycle stuff here lately.

[crazy steve]

K&N air filters are more about a successful marketing campaign then a superior air filtering technology.....
.....While they may may pass a bit more air than a paper filter when freshly cleaned and oiled, the added gain by a non-specialty built engine is, at best, negligable....

In K&N's defense, there have been documented tests in specific applications where their filter did produce more power than either an open intake or a competing filter design (and these weren't 'cold-air' conversions either). So there are times when they can actually produce more power. But as Mike said, they took that specific info and claimed it across their whole product line, definitely a bit of a stretch.

One particular case had some interesting fallout... HD sold a jointly-developed-with-K&N 'off road' (Screaming Eagle) air cleaner for their bikes until early '04, and the unit for the Sportsters was dyno-tested as superior to almost all other competing types. Then HD and K&N got in a contract dispute, and HD switched to a paper filter (rumor has it made by Fram) instead. To get the same airflow, they used some sort of 'special paper' media; only problem, the first-sold filters started disintegrating within a month or two in use, and by the time they got the problem 'corrected', the extra HP had gone away... so the filter was worth a bit of power.

[cywelchjr]

I think that's a good point Tom, and one I have thought about a good bit myself. I've thought hard about going back to paper on my Camaro when I get it back on the road, and may well do so, but IIRC, the stock filter on our bikes isn't paper anyways, it's a type of foam filter anyways, so going to an aftermarket foam filter seems to not be a problem that I can see (I've not actually seen a stock XS11 filter, but all the other stock XS filters I've seen from the era were a thin foam material, and were intended to be cleaned out by blowing them out several times before being replaced), so I'm not worried about my UNI foam filter in my stock box, as it's pretty much about 3 times the material in the same form as the stock filter, but fully washable.

[tri650]

No changes will be made

After a few test rides I will not change a thing. This bike is running awesome. Scary fast and smooth as can be. Pick up and go throughout the entire RPM range. I have not synched the carbs or done anything to them other than install. I am guessing I will get antsy this winter and take them off and take them apart and probably screw up this fine running machinge - but that is why we have these boards. I'll let you know when I need help.

[3Phase]

... I am guessing I will get antsy this winter and take them off and take them apart and probably screw up this fine running machinge - but that is why we have these boards. I'll let you know when I need help.

Fix it until it breaks, then keep fixing it until it works again.

[Bonz]

I've run K&N's in about every kind of gas powered device I've owned, save for my Craftsman lawnmower... Do they make one for that????

The best example for sheer mileage would be the various Cherokee's/Grand Cherokee's I've owned over the years. I am not after the power factor, it's the sheer convenience of cleaning, drying, re-oiling and RE-USING.

As for my motorcycles, the only bike I didn't run one in was the Honda ST 1300 that I had for about a year, and it had a new factory element in it so if I kept the bike, I would have put in a K&N.

I'll say that convenience is the #1 factor in using them. In the case of my current "other bike" (ZRX 1200) I have the pod filters on and the bike is coming up on 30,000 miles with absolutely no issues in terms of wear and tear. Carb accesss is grand, so if I ever do want to play around with jetting, adjustments, etc, it's cake.

For the XS, think about where the snorkel is, and I can't see a huge difference in what that filter will let the engine digest quite honestly. Snorkel facing rearward, under the seat, etc...

In fact, I just did an oil change on the ZRX, getting ready for the slowing of the riding season and winter coming on here in Colorado, and sent a sample of oil to Blackstone for analysis. I had just over 4,000 miles on that oil so should give plenty of feedback. If there is any undue particulate matter in the sample, they'll note it and let me know. I'll pass on the info when I get it back as well, maybe it'll help with this discussion.

To me, it's not about what size particle makes it through as much as it is what engine wear is taking place? The particles a K&N let through may be larger in the purest sense, but what is the size threshold that it can make a difference? Again, the oil analysis will tell if there is any silica (dust, dirt from poor filtration) in the oil, abnormal wear, etc. But based on the fact the ZRX doesn't use oil per se, over a 4,000 mile interval, that tells a whole lot about the internal condition of the engine in my eyes.

In any case, I just have to look at all the cases and millions of miles that vehicles in general run when fitted with K&N filters, and I don't see a stone's throw worth of difference in longevity and a whole lot more convenience and long term cost benefit.

[Bonz]

Oil analysis w/ K&N pod filters!

I can't believe the lack of participation on this particular thread! Geez, a Final Drive swap creates rifts and chasms amongst us, but the air our bikes breathes seems to not interest folks much!

I spiced up the thread with a new title for my post, so maybe that will get things moving a bit.

Just got back my Blackstone Labs oil analysis for the most recent oil change I did on my 2001 ZRX 1200. The oil tested was Motorcraft 15w-40 Diesel oil.

The main point in sharing here is my silicon level was a 4, with universal averages for oil being 5.

This means with 4 pod filters allowing the carbs to suck unholy amounts of God's great air (that my beloved 80 SG could only dream of flowing) into that 125 hp/80 ft-lb torque of a beast-engine, the silicon readings are great. Insolubles were at a value of .2 and a value of >.7 is desired, so the oil fitler is doing it's job very well also.

With that said, I did the oil change at just over 4000 miles of use on the oil, and their averages are for 2500 miles between changes, so it's even more notable in terms of the low amount of silicon in my engine.

Every other wear metal was below wear averages (still keep in mind I ran a 4,010 mile OCI vs their averages are based on 2500 mile OCI's), and the bottom line is with just under 30,000 pod filter miles on that ZRX 1200 engine, it's doing just as good as a bike with a stock filter element in Blackstone's estimation. Yes, I asked them that question.

Hope this thread gets some more play, it will help folks shed some light on stuff.