Topic: K&N air filter?

[emilios]

Hi
i bought a K&N air filter for my CB750 K0 and i just saw that it writes on that u have to apply oil on it...
Why??

[Ujeni]

Thats how all K&N air filters work: you apply their special oil to the filter each time you clean it (or the first time you install it).

Without the oil, you won't be able to clean the filter for second use (and I suspect that it won't filter the air as well either).

[dhall57]

I run K&N's in both my 750's. The new filters come pre oiled and are ready to use. Says it right on the wrapper the filter comes in. But what I've done with mine is always get the cleaning kit they offer and before installing is clean them good and then lightly oil them. I think from the factory it's saturated with to much oil IMO.

[Powderman]

I run K&N's in both my 750's. The new filters come pre oiled and are ready to use. Says it right on the wrapper the filter comes in. But what I've done with mine is always get the cleaning kit they offer and before installing is clean them good and then lightly oil them. I think from the factory it's saturated with to much oil IMO.

It often amazes me how guys think they know more than the 1000's of hours put into developing an item by qualified engineers.
The oil is what all the debris sticks to so that the filter element can be slightly bigger for airflow yet still filter the crap out of your intake. Without the oil it would allow too much debris in your motor eventually causing premature wear on the rings, bores, valves, etc.

[dhall57]

Pman I did not say I ran my filters without oil just less of it. And by the way what I said to do was not something I came up with thinking I knew more than the engineers, its what a K&N rep told me to do that came into my place of work

[tlbranth]

I put a K&N on my 750. It wasn't clear to me if it needed oiling so I called the manufacturer and they assured me they come pre-oiled. Later there was a thread on one of the forums I regularly hang out at and someone commented that K&N did not filter all that well. "Pshhh", I said, and went on a search for data to prove him wrong. He was right. In the test I read, which I cannot now find, K&N was rated dead-last, or close to it, in filtering capability. I already had K&N on 2 of my bikes but bought OEM for the other 2. I'll see if I can find the test and post it.

[tlbranth]

Found the test.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

[HondaMan]

Found the test.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

Interesting study, but it doesn't seem to match up to "real life"...from my [most recent] example:

I just took my own 750 down at 90k+ miles on the .25mm overbore I did in 1980. I bought the K&N filter for it in 1972, when the first paper (Honda) filter had 8k miles on it, and was not yet plugged, but the bike was apart following a wreck. So, it has had (the same) K&N on it since 1972.

In 1980, after getting married and thinking I needed to rebuild it before I had no more $$ for it, I disassembled the engine and found zilch wear inside, unmeasurable in any dimension, in the top end. I already had the piston kits, had it bored .010" (0.25mm) anyway, lapped the valves, back together.

Fast-forward to 2006, at 126k miles, still using the same K&N filter, cleaned exactly 2 times since the 1980 rebuild...no measurable wear in any bore (and I can reliably measure to less than .0001"), valve faces showed no erosion. Put it back together with new gaskets (it had been sitting 5 years while I had cancer fixed, was weeping at the cylinder base gasket from sitting alone too long).

Last Spring, 2013: took it down at 138k miles because of nasty oil leak (induced by a monster storm here that damaged the cam cover gasket) and ahead of time had bought some .5mm overbore pistons, just in case. It had a large vertical scratch on 70% of the #1 stroke, caused by a chunk of hard carbon caught above the compression ring, bored to 0.75mm just to be sure it was gone. But other than this scratch, STILL no measurable wear in any of the 4 cylinders, valve faces all beautiful (and in fact went back in with a touch-grind and polish treatment).

All this time: the same K&N air filter. I did buy it a new one for this rebuild.

Meanwhile: I have received 4 CB750 bikes (whole) in the last 5 years for rebuild. All had less than 25k miles except one, all were original, as noted by the OEM parts found during disassembly. All had Honda paper air filters except one (unknown aftermarket, suspect EMGO), and at least 2 of them were original bike owners. All 4 bikes suffered notable grit wear in the top ends, both on the faces of the intake valves and the sides (over the wristpins) of the pistons where dust tends to accumulate during overlap operation. Dust ingress causes small vertical scratches on the sides of the pistons, above the wristpins, easily ID'd by the experienced eye. (BTW: 4-stroke dirtbikes suffer this a lot.) All 4 engines had enough measurable wear to determine a rebore was a good idea (2 became 836cc engines).

While this is just one example, I have seen many, many more. It's also interesting to note that Ford has supplied the K&N filters in the Explorer as OEM for a long time, too. Those engines are known for exceptional top-end longevity, at least here in CO. The typical Explorers around here all have near or more than 300k miles on them, without so much as a valve job. Heck, their trannies wear out first(!).

I would have to say I vote a "jaded eye" toward this website's study, as it doesn't take into account several things. One of the most important that I know about is: the K&N gauze-wire design, now copied by almost 30 other bootleggers (including a garage-shop I know here in Littleton), cleans air better as it gets dirtier (they don't FLOW better, but the FILTER better...so, you must start with an oversized one, which certainly is the case with the one for the 750). This has been known, and shown, for many years. What I have noticed on the ones on my cars and bikes over the years: even when they are so dirty as to have to be brushed clean because they are caked with dirt, leaves, bugs, and grit, cleaning and re-oiling them made no change in power or MPG on any of the vehicles I have, i.e., the engines ran the same before and after cleaning. This list includes: 1967 Ford w/390 CID engine, 1979 Ford w/200 CID engine, 1977 Dodge motorhome w/360 CID engine, 1990 Lincoln w/5.0 liter (aka 302 CID) engine, and 1996 Explorer with 4.0 V-6. All but the Explorer started with paper filters, all have K&N now, all (that I changed) got better MPG and mountain-climbing power when I installed the K&N.

This just doesn't stack up against the claim(s) I see 'against' the K&N on that site?

[Powderman]

Pman I did not say I ran my filters without oil just less of it. And by the way what I said to do was not something I came up with thinking I knew more than the engineers, its what a K&N rep told me to do that came into my place of work

My reply was to your comment about how you felt the factory puts too much oil on their product, not what you did after you received them. K&N is one of the most advance air filters in the world. To imply that they err by putting too much oil on them just made me smile. Did the K&N rep say they were oiled too heavily and to strip and redo them?

[dhall57]

Yeah he said in some of cases they do come to heavily oiled and it would cause customers to complain of having excess oil in the bottom of air box and vehicles running worse after installing the new K&N. I guess because to much oil blocks air flow. So this is what they suggested they do in those cases.

[tlbranth]

Found the test.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

Interesting study, but it doesn't seem to match up to "real life"...from my [most recent] example:

Hmmmmm, now what?

[Powderman]

The problem in choosing an air filter is a compromise at best. You either want it to do the best job of filtering debris or provide the most efficient amount of unrestricted airflow to the motor. The more you filter debris the more it restricts air flow. While a K&N may not filter as much as some filters they will provide the more unrestricted air to the motor. They also are 1,000,000 warranteed so they will last the longest for your dollar spent. Most people I know that choose K&N filters do so more for performance advantage than purely to provide clean air to the motor.

[HondaMan]

Found the test.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

Interesting study, but it doesn't seem to match up to "real life"...from my [most recent] example:

Hmmmmm, now what?

Roger that! ?

[ofreen]

Interesting study, but it doesn't seem to match up to "real life"...from my [most recent] example:

(snip)
This just doesn't stack up against the claim(s) I see 'against' the K&N on that site?

 

I'll add my two cents worth.  The K & N air filter debate is a never-ending one.  Here are a couple of times I've chimed in on it -

http://forums.sohc4.net/index.php?topic=30589.msg314926#msg314926

http://forums.sohc4.net/index.php?topic=98901.msg1103600#msg1103600

The only change since the last time I posted about this is the engine is now at 144,820 miles.  The K & N air filter hasn't ruined the engine yet, despite  the naysayers.  As I've said before, the filter has to be oiled correctly and the sealing grease must be used.  And I agree with Dhall57.  I've seen some of them with too much oil from the factory.

[HondaMan]

Interesting study, but it doesn't seem to match up to "real life"...from my [most recent] example:

(snip)
This just doesn't stack up against the claim(s) I see 'against' the K&N on that site?

 

I'll add my two cents worth.  The K & N air filter debate is a never-ending one.  Here are a couple of times I've chimed in on it -

http://forums.sohc4.net/index.php?topic=30589.msg314926#msg314926

http://forums.sohc4.net/index.php?topic=98901.msg1103600#msg1103600

The only change since the last time I posted about this is the engine is now at 144,820 miles.  The K & N air filter hasn't ruined the engine yet, despite  the naysayers.  As I've said before, the filter has to be oiled correctly and the sealing grease must be used.  And I agree with Dhall57.  I've seen some of them with too much oil from the factory.

Out of curiosity, "O": how often have you clean & oiled yours? I have been going with the 25k mile rule, myself.

[ofreen]

Out of curiosity, "O": how often have you clean & oiled yours? I have been going with the 25k mile rule, myself.

I do that every couple of years, so about 10-12,000 miles.  I still live at the end of a gravel road, plus I get the urge once in a while to do some cow trailing on the bike.  So it is usually plenty dirty when I get around to cleaning it.  The intake horn on the filter housing is not too far in front of the rear tire, so that probably has something to do with the accumulation.  It didn't get dirty so fast years ago when I lived just off the pavement.  That is one reason I don't buy the "K & N filters pass a lot of dirt" claims.  The bike gets subjected to a lot of dust.

[HondaMan]

Out of curiosity, "O": how often have you clean & oiled yours? I have been going with the 25k mile rule, myself.

I do that every couple of years, so about 10-12,000 miles.  I still live at the end of a gravel road, plus I get the urge once in a while to do some cow trailing on the bike.  So it is usually plenty dirty when I get around to cleaning it.  The intake horn on the filter housing is not too far in front of the rear tire, so that probably has something to do with the accumulation.  It didn't get dirty so fast years ago when I lived just off the pavement.  That is one reason I don't buy the "K & N filters pass a lot of dirt" claims.  The bike gets subjected to a lot of dust.

Ah, yes, the backward vent on the post-1974 bikes! Good for hiway, not so much for gravel and dirt. I went through a major sandstorm on a tour with my brother in 1978, in NM. It took most of the paint off the left side of our fairings in about 50 miles, it was that bad, but we leaned down inside the Vetters and all we "lost" was the windshields (sandblasted!) and paint. His paper air filter (CB500-4) was clogged the next AM, routing us to a bike shop in the next town on the next day. While he changed his, I pulled my K&N out and looked at it, very dirty: we finished the next 4000 miles with mine like that, ran perfectly the whole trip home. Never fouled a plug, nothing.

Like you, I don't understand this "test data". (?)