PDA

View Full Version : K&N Air Filter Install - HELP!



burnszilla
06-24-2004, 05:55 PM
I bought a K&N air filter for my 87 K75S and tried to install it. After 20 minutes I gave up.

What a pain in the butt! The stock filter slides in easily and fits.. I can't get the air box to snap tight around the K&N filter?? I read the instructions and followed them.. but it appears that the filter is just a little too long.

Any suggestions to get this filter in easier?

Thanks.

deilenberger
06-24-2004, 06:32 PM
Originally posted by Burnszilla
I bought a K&N air filter for my 87 K75S and tried to install it. After 20 minutes I gave up.

What a pain in the butt! The stock filter slides in easily and fits.. I can't get the air box to snap tight around the K&N filter?? I read the instructions and followed them.. but it appears that the filter is just a little too long.

Any suggestions to get this filter in easier?

Thanks.

Suggestion - return the K&N and reinstall your stock filter.

The K&N provides NO advantages and lots of disadvantages. If you need data on it, see:

http://www.ibmwr.org/ktech/dyno/index.shtml

These tests were done on a K100, which requires 33% more air than your K75.

There are also links around that show how much worse the K&N filters than a standard paper filter... don't have them handy, but a bit of work with Google will turn them up for you.

Oh - the K&N doesn't fit because it isn't the same dimensions as the stock filter, plus the stock filter has a lip removed on the top/back edge so it can slide in. Just another example of the fine engineering K&N provides.

BTW - my current K75S came with a K&N installed by the previous owner. My first project was to replace it with a stock filter. I then gave it away since I'd feel guilty selling the damn thing.

BTW-II - a stock filter on a K75 is good for 100k miles or so provided you don't go riding in dust or sand storms. The design is such that anything captured by the filter drops to the bottom of the airbox and sits there (bet you found some stuff there right?) It's a clever design, and I personally know peope with well over 100k miles on a stock filter and no performance degredation.

Best,

paulsibek
06-25-2004, 04:43 PM
I tried and took mine to the dealer and they installed it for free.

It's a patience tester for sure.

paulsibek
06-25-2004, 04:47 PM
Mine works fine in conjunction with the Staintune exhaust. Noticable power increase.

Most likely the stock filter and exhaust are designed to work together, but I am VERY happy with my setup. Power from 5k rpm is WAY better compared to stock.

FRUBIO
06-25-2004, 07:58 PM
A good friend had to assist me in installing the K&N filter in my 93-K1100LT. It took alot of "talking" and holding your jaw just right but finally went in. Made me wonder if I was doing the right thing for a while. I hads had a little better gas mileage with it and have a little more throatier sound.
In retrospect I am not sure if it was the right thing to do but it works!!!!!! :dunno

burnszilla
06-25-2004, 08:06 PM
i returned the air filter.

deilenberger
06-27-2004, 03:36 AM
Originally posted by Paul Sibek
Mine works fine in conjunction with the Staintune exhaust. Noticable power increase.

Most likely the stock filter and exhaust are designed to work together, but I am VERY happy with my setup. Power from 5k rpm is WAY better compared to stock.

Paul.. question:

Aside from a butt-dyno do you have any data on the power improvement?

I have done runs with StainTune and a K&N filter. The restrictive part of the flow through a K engine is not the intake or exhaust, it's the valves. Without changing the cams or going to oversized valves (which were done to my K75S) - you're not seeing more power.

It may sound like more power to you.. but without a dyno to back it up, I don't believe it.

I've dyno'd about 7-8 K bikes now - with all sorts of combinations of "go-faster" bolt-on stuff. NONE of it improved over the stock equipment. Some of it - such as the K75 Staintune - made things considerably worse.. a loss of > 25% of midrange power.

If you're interested in more - you can see the website I posted in the message above, or you can look at my personal website - the data on the K75S StainTune is there.

http://www.eilenberger.net

Here is the direct link to the dyno runs I referred to:

http://www.eilenberger.net/k75exhaust/index.html

Worth noting - the first bike also had a K&N air filter, and a modified fuel pressure regulator - the usual combo of "go-fast" stuff from some not too scrupulous dealers.

I'm guessing you didn't go to:
http://www.ibmwr.org/ktech/dyno/index.shtml

Something that may or may not be significant to you - in some of the dyno testing we performed we decided to see how oversized the K bike air filters are - so we blocked off 50% of the surface area with SaranWrap{tm} -- it made NO difference.

We tested with NO air filter, a used stock filter and a freshly treated K&N filter. There is no measureable change of power.

I also have dyno plots somewhere of my old K100RT, with stock exhaust vs the Staintune Sport exhaust for the K100 engine. This one was reasonable in that it didn't LOOSE power. It also didn't make any more power, but at least it was pretty and a bit lighter than the stock system.

BMW isn't so dumb that they would leave HP laying on the table waiting for someone to just come along and pick it up.. they seem to have the talent, money and motivation to maximize power right at the factory. Go figure..

Best,

deilenberger
06-27-2004, 03:37 AM
Originally posted by Burnszilla
i returned the air filter.

Stephen - good move. Dust off the stock one and it should be fine for lots more miles..

Best,

pj1150r
02-22-2007, 06:35 PM
i have a brand new one still in box for my r1150r.after reading all this,i wont be using it.anyone want it?

st3ryder
02-22-2007, 09:19 PM
I've used a K&N filter in my '87K since I got it about 8 years ago. IIRC, it sits with its lip outside the air box, ie its outer groove slips into the lid/bottom shell. I didn't get it expecting any perfromance enhancement, just a long, service free life. I took it out for the first time since I installed it after approx 30k miles on the bike, (it been a second bike for approx 6 years) last year when I replaced my throttle cable, and it looked as clean as the day I put it in. There was some dust/sand at the botom of the air box as was mentioned. I find the snaps are the real pita to replace, not slipping the filter in. The stock paper probably works just as well, but *will* need replacing more often IMO, as it's more restrictive. Though there's been some talk about no performance improvement, nobody's mentioned the stock filter will flow less air over the same time. I wonder if there's been back to back dyno runs with a paper filter with 20+K on it vs a k&n with 20+k. That might give give a better idea of which filter's performance lasts longer and that's what it's about, yes?

OfficerImpersonator
02-22-2007, 10:34 PM
Suggestion - return the K&N and reinstall your stock filter.

The K&N provides NO advantages and lots of disadvantages. If you need data on it, see:

http://www.ibmwr.org/ktech/dyno/index.shtml

These tests were done on a K100, which requires 33% more air than your K75.

There are also links around that show how much worse the K&N filters than a standard paper filter... don't have them handy, but a bit of work with Google will turn them up for you.

Oh - the K&N doesn't fit because it isn't the same dimensions as the stock filter, plus the stock filter has a lip removed on the top/back edge so it can slide in. Just another example of the fine engineering K&N provides.

BTW - my current K75S came with a K&N installed by the previous owner. My first project was to replace it with a stock filter. I then gave it away since I'd feel guilty selling the damn thing.

BTW-II - a stock filter on a K75 is good for 100k miles or so provided you don't go riding in dust or sand storms. The design is such that anything captured by the filter drops to the bottom of the airbox and sits there (bet you found some stuff there right?) It's a clever design, and I personally know peope with well over 100k miles on a stock filter and no performance degredation.

Best,

Don,

You've got decades more experience that I do with a K75s. I have a Staintune exhaust. I think it sounds really neat, but if it's impairing the performance of my bike, should I replace it with stock?

Considering your expertise, I respect your judgment.