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  Topic Review (Newest First)
02-19-2012 10:53 PM
VN750Rider/Jerry An oiled foam filter is the most efficient filter made. All dirt bikes have them. And they are inside of an airbox, with a snorkel to let the air in, designed in such a way as to let in as little dust as possible. And unlike streetbike riders, you won't find dirtbike riders using pod type filters. The reason those type of filters (of any brand) are not much good is they are a paper thin mesh, with large holes in them. You can hold them up to the light, and see light through them. Try that with a well oiled stock foam filter. The difference is twofold. One, the stock filter is much more dense than an aftermarket "high flow" filter. Two, the stock filter is also a lot thicker than an aftermarket "performance type" filter. When you have a dense thick well oiled filter, virtually nothing is going to get through it. Oil is sticky, and acts like a magnet on dirt. And the dense thick foam filter, it has plenty of room to catch and hold that dirt. I have never seen a properly maintained stock oiled foam filter get ANY dirt on the back side of it, even on a dirtbike, where the outside the filter is so caked with dirt it is falling off in chunks. But it needs to be cleaned and reoiled often, because those chunks are composed of a mixture of dirt and oil, and eventually the dirt will suck all the oil out of the foam, leaving it useless as a filter.

KM is right, an K&N "filter" will not destroy your engine right away. But according to my calculations, based on all the K&N test data I can find, using them, especially the pod type, will knock about 30% off the life of your engine. Now, I figure the life of a properly maintained Vulcan 750 engine to be in excess of 100,000 miles (Hopefully I will someday be able to find out. I'm past 70,000, but don't have the riding time I used to).

However, things add up. If you don't properly jet for those filters, you will be running way lean, which will shorten engine life any more. And if you cut up the stock exhaust system, you will put the backpressure beyond the range of which the carbs can be tuned for the entire usable rpm range. It will be spot on only at a very narrow range, too rich at some speeds, and too lean at others. That will actually do more damage than the poor quality air filters. And if you use those kind of filters, you will need to change the oil and filter a lot more often, because it will get dirty a lot faster.

If you do the earshave but don't rejet, knock out your baffles or remove the goats belly, and don't change your oil, you will likely cut your engines lifespan more than 50%, and I consider that a conservative guestimate.

It's you engine, and you can modify it anyway you want. The reason I keep repeating this is because I believe a lot of people are making these modifications, sometimes based on the advice of others here on this forum, without realizing the damage they are doing. If that damage does not bother you, then by all means go ahead. But I do suggest doing a lot of research before doing ANY modification.

When you modify something to make a gain somewhere, you will invariably lose something somewhere else. The factory design is a compromise, designed to be acceptable everywhere. The Vulcan engine is a mixed bag. On one hand, it shows poor design, by using way more parts than were necessary. On the other hand, if left alone and properly maintained, it has shown to be very reliable in stock form.
02-19-2012 09:55 PM
Knifemaker Fireman...

Don't let Jerry scare you away from doing what you want to your bike. First off, I have yet to read any side by side tests of K+N Motorcycle filters against stock motorcycle filters.

There are thousands of riders using K+N filters, and no real proof that using them will cause premature engine failure. But, the logic of less is better is well understood. If long engine life is your primary reason in owning your bike, then I'd have to advise against doing an earshave to start with.

But, some of are more interested in riding a bike that suits their style, that looks the way they want it to and puts performance over longevity.
I've owned several bikes that I ran K+N pod filters bolted right to the carbs. I of course had to rejet ... But the increase in performance was more important to me than anything else. I put thousands of miles on the bikes, but admit I sold them/traded them before I had the opportunity to find out how many miles the engine had left. And frankly I at the time didn't care.

If you like the way the bike looks without ears, then take them off. Don't matter if you run K+N pods or Emego Foam pods, your going to need to rejet. If get the right exhaust, you'll get more power, but anytime you do this, you're going to shorten engine life even if you have the best filter in the world.

Bikes don't need to last forever. They can break down for hundreds of reasons ...and if you want to keep them forever, they can always be fixed or rebuilt.

So, do what makes you happy. Life is short.
02-19-2012 08:13 PM
firemancc91 As I am one to readily admit that I am wrong. After a little searching I did find information to up hold Jerry's statement regarding filtration efficency. As all of my previous info was based upon info presnted to me by a few persons working for a local service shop that was a K+N distributer. I have apparently fallen pray to the hype of a salesman. I did find some info on K+N filters better flow and here is a link as to such. However all the info is regarding passenger cars not MC's. Are MC engines really any more suseptable to damage from dust, then passenger cars?


There were also other sites and blogs noting real world test that show K+N's flowing better. Most of what I found was subjective based upon the veiws of the tester. As the stock vulcan filter is an oiled foam filter, just like the high flow foam aftermarket filters. It doesn't seem to me that there would be much difference in filtration efficency. So its, IMO, really a matter of what your looking for, flow vs filtration. As I am still going to do the ear shave and am not sure of the dust damage issue. I am going to do more research on filters and flow vs filtration. If I can find an aftermarket filter with similer CFM's to the stock filters and have high filtration efficency then that's what I'm going with.
02-18-2012 09:02 PM
Originally Posted by firemancc91 View Post
Ear shave for sure. K+N filters are recommended. As they are an oiled high flow filter they are as good or better then stock. K+N's are proven and tested to filter better the OEM filters and flow better.

I'm going to use them myself. The P/O for my bike did the "Coastering". So I'm going to complete the process and remove the pods and surge box

Go with the ear shave. Look in the Carbs and Fuel threads for VoId Docs' ear shave procedure. It a greatly detailed how to.
Unfortunately that is not the case. K&N filters have certainly been tested plenty of times, and every single time they have failed miserably compared to stock filters. Do your own research online. I could post enough information on it to crash the server. I have posted at least 20 different tests already, here is some more information, from a BMW car forum.

Rob Levinson from UUC Motorwerks says that "it is really doing every E34 owner a disservice for three reasons:
First, conclusive tests from independent labs show that K&N filters, no matter how well-oiled and cleaned, let through huge amounts of large particulate that damages engines. Oil analysis shows 5x as much silicate contamination. Additionally, the oil from these filters tends to muck up the MAF and cause an engine-damaging lean-run condition.
Second, an open element filter like that sucks in hot underhood air and subjects the filter to "fan wash", the swirl that creates a vacuum effect. On the E36 M3, we measure a 15hp loss from open cone filters.
Third, the E34 airbox is designed with an integral velocity-stack style venturi at the opening. Running one of these engines on a dyno, you can cause a 5hp drop just from putting your finger on the stack lip. Removing that airbox undoes a lot of good BMW engineering. Yes, these filters make a "really cool" noise... but noise does not equal power. Stick with a stock paper element in the factory airbox, you're not getting any more power with a K&N garbage-filter, just damaging your motor."

Jim Conforti (AKA the Land Shark) did some testing:
This was a scientific test, not one done by filter manufacturer X to show that their filters are better than manufacturer Y. The test results are pretty irrefutable as the test lab tests and designs filters where "screw ups" are absolutely NOT allowable (I can't say any more for security. Think "Glow in the Dark").

A scientific test was done on TEST filters where air was loaded with ACCTD (some standardized "test dust" called AC Coarse Test Dust) and sucked through the TEST filter then through an analysis membrane. From the Quantity of dust injected and the amount that gets through the TEST filter and is then captured on the analysis membrane we can calculate the efficiency of the TEST filter in Question.

BMW Stock Filter, Eff. Area of Media: 8.4 sq ft.
K&N Replacement, Eff. Area of Media: 1.6 sq ft.

The filters are the SAME size. They both fit in the STOCK BMW M3 airbox. The difference is that the STOCK filter has 65 pleats 1.5" deep and the K&N only 29 pleats each 0.75" deep.
Now, remember this ratio: " 5.25:1". It's the ratio of the AREA of STOCK to K&N. It's very important and will come into play later.

The STOCK filter efficiency started at 93.4% at 0 loading and increased to 99.2% efficiency as the loading increased to a max tested of 38.8 gm/sq ft of dust.

The K&N filter efficiency started at 85.2% at 0 loading and increased to 98.1% at the max tested loading of 41.38 gm/sq ft.

Now, I hear you. "Jim, that's only a FEW PERCENT". But is it?

Let's look. If we had 100 grams of dust on a new BMW filter we would let through a total of 6.6 grams of dust in. If we used the new K&N filter we get 14.8 grams of dust. That's 224% (TWO HUNDRED TWENTY FOUR PERCENT!!) more dust ingested initially, stock vs. "free flow" and this ratio is pretty much held. Somewhere between 200-300% more dirt gets "ingested" anywhere across loading equivalence. The more INTERESTING thing is when you look at what happens to the DP or Differential Pressure at a constant airflow as you dirty both filters equally with time.

The test used a rate of 75gr of dust per 20 min. Here's where the AREA difference comes MAJORLY into play. See, even though the BMW filter flows a bit less at the SAME loading, it also LOADS UP 5.25 times SLOWER due to it's LARGER effective area. So what happens is that the K&N initially flows better, but as the dirt continues coming in, the K&N eventually flows WORSE while still letting MORE dirt in.

Now, does any of this additional dirt cause problems? I dunno. I suppose we could have a few people do some independent oil analyses on different motors using both K&Ns and Stock filters. Get enough of them, and you'd have a good statistical basis. For me though, it's simple: More DIRT = BAD.

The additional short-term airflow might make sense on a track car. IMHO, it doesn't for the street.

-- Jim Conforti
02-17-2012 09:00 PM
firemancc91 Ear shave for sure. K+N filters are recommended. As they are an oiled high flow filter they are as good or better then stock. K+N's are proven and tested to filter better the OEM filters and flow better.

I'm going to use them myself. The P/O for my bike did the "Coastering". So I'm going to complete the process and remove the pods and surge box

Go with the ear shave. Look in the Carbs and Fuel threads for VoId Docs' ear shave procedure. It a greatly detailed how to.
02-16-2012 08:47 PM
VN750Rider/Jerry Just noticed the "degoated" part. Not a good idea. removing the exhaust crossover chamber will put the backpressure all over the place, depending on engine speed. The carbs do not have enough adjustment to compensate for it over the entire usable rpm range. If you want a louder exhaust, I suggest getting an aftermarket system designed for the Vulcan 750, and tuning the carbs for it. While aftermarket pipes have less backpressure overall, it is a lot more consistent over the entire rev range than a butchered stock system.
02-16-2012 08:07 PM
Originally Posted by The DEUCE View Post
Awsome, ive heard of the ear shave but wasnt sure what it was exactly. I will look into it probuletly after my first few mobs (r+r relocation and replacement, meanstreak seat, rear fender off 1500) thanks for the info though
02-16-2012 07:13 PM
VN750Rider/Jerry I don't like the airbox setup either, it's way too complicated, and I like simplicity. To that end, I removed every unnecessary part I could find from my bike. But I left the complete stock intake system. The reason is because I could not find any aftermarket filters that I would consider good enough (at filtering) to use on the bike. The stock filters are far superior in that regard than any aftermarket pod type filter I can find. Since I am mostly a highway rider (70,000+ on my bought new '02), engine longevity is of paramount importance to me. The "earshave" thing may look better to some, it even appeals to me because of it's simplicity, but I just don't consider the decrease of engine life to be worth it. I want every single mile out of my engine I can get. If you are a short distance rider, and don't rack up a lot of miles, then it might be different, but I still cringe when I think of all that dirt going through the engine, slowly grinding it up.
02-16-2012 06:44 PM


02-16-2012 06:36 PM
Air Box needing some work

So I have debated this for a while now.
Im not a big fan of the stock air box, its bulky and just doesnt look as smooth as the bike should. what can I do for a mod or replacement to give the bike a better look? thanks

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