Hi all
Just finished most of the resurrection works on my K100RT (early 1985) that was idle for more than 8 years.
Satisfied so far , took her for a couple of short rides almost 200km put on it since past Monday.
One of the things i didnt change is the air filter. 
Read a lot about air filters, etc and i m between a Bosch Air filter and a KN BM2605 one.

As i see from my notes the last time i changed the filter was at 100.000km (2001)  and now i m at 108.000 

Mechanic ( which i dont trust ) said he checked it and it's fine just cleaned/lubed it but didnt changed it.

Should i change it? 

What is a typical symptom to indicate changing? Bike responds very positive to any gas twist in the whole rev range.

They last well but are paper filters so you don't lube it so I am not sure what he says. 8,000km would not mean you need a new one. My only concern is if the mechanic did actually check it but that's easy to do. My own thought is after 17 years to get a new one but not bothered about a Bosch one, lots of others will work fine and they are easy to fit once you know how.

What kind of filter is in the bike now?

If the mech said he have cleaned and lubed it it's probably a K&N or similar
which shouldn't be changed....only cleaned and oiled.
The negative side is that it lets more dirt through than the original paper filter.

Thank you both
Have no clue what's inside that box. I'll give it a check this afternoon and post some pics. I doubt its a KN one. He would have mentioned.
So if its a paper one goes to the recycle bin. If its a fibre based KN or such stays.

You live in a very dry climate with means a lot of dust in the air filter. IngeK mentions how the K&N lets more dust through.....think I would be putting in a paper one.

92KK 84WW Olaf wrote:You live in a very dry climate with means a lot of dust in the air filter. IngeK mentions how the K&N lets more dust through.....think I would be putting in a paper one.

Copied that  i'll try my best to find a paper one. The plus for KN is that its readily available . 
Thank you !
Breathing looks and sounds fine on the lady so far. Only complain is that for a couple of times when starting up i get something like poor mixture indication. Idle struggles to keep steady, after little choke play goes back to normal. But this happened yday after 4 hours of leaving the bike in the garage with air temperature around 30 C so its not justifying this behaviour.

If I found a K&N filter in the air box(found one when I got one of my bikes) I would bin it immediately.  They don't offer any performance benefit and let in a lot of dirt compared to paper filters.

With a paper filter there are two checks I do.  Tap it on a clean piece of paper, does any dirt shake out?  Can you hold it up to the light and see light coming through between the folds?  If dirt shakes out or you can't see any light, you need a new filter.

Another issue with oiled air filters is that the oil gets "cooked off" more quickly than with most engines due to where the air filter sits and the heat it gets exposed to so you need to cut the recommended filter maker's maintenance cycle by half or so. So aside from letting more crap through it also requires tons more maintenance than a paper filter.

Also the size of a K filter is HUGE for a 1 liter engine so the BMW service interval of 12,000 miles is silly.  I change every 50,000 miles and even that is overkill.

WIX makes a K air filter which I think is where BMW gets them.

duck wrote:Another issue with oiled air filters is that the oil gets "cooked off" more quickly than with most engines due to where the air filter sits and the heat it gets exposed to so you need to cut the recommended maintenance cycle by half or so. So aside from letting more crap through it also requires tons more maintenance than a paper filter.

Also the size of a K filter is HUGE for a 1 liter engine so the BMW service interval of 12,000 miles is silly.  I change every 50,000 miles and even that is overkill.

Understood
If we assume that in my case its a paper filter. Problem is not the mileage, its less than 8000km but should i be worried for the 18 years of its life in that box?

Point-Seven-five wrote:If I found a K&N filter in the air box(found one when I got one of my bikes) I would bin it immediately.  They don't offer any performance benefit and let in a lot of dirt compared to paper filters.

With a paper filter there are two checks I do.  Tap it on a clean piece of paper, does any dirt shake out?  Can you hold it up to the light and see light coming through between the folds?  If dirt shakes out or you can't see any light, you need a new filter.

You can also clean a used paper air filter some by vacuuming the input side or blowing air on the output side.  If you have it out to check that costs nothing.

George_Pap wrote:

duck wrote:Another issue with oiled air filters is that the oil gets "cooked off" more quickly than with most engines due to where the air filter sits and the heat it gets exposed to so you need to cut the recommended maintenance cycle by half or so. So aside from letting more crap through it also requires tons more maintenance than a paper filter.

Also the size of a K filter is HUGE for a 1 liter engine so the BMW service interval of 12,000 miles is silly.  I change every 50,000 miles and even that is overkill.

Understood
If we assume that in my case its a paper filter. Problem is not the mileage, its less than 8000km but should i be worried for the 18 years of its life in that box?

In theory in an extremely moist climate that can cause the filter fibers to swell over time.  But that's theory.  In real life that's nothing to worry about.

If I were you:

1 - Current filter is oiled type:  Clean/reoil it until you can obtain a paper one.

2 - Current filter is paper.  Use it and worry about something else like using synthetic blinker fluid.

duck wrote:


2 - Current filter is paper.  Use it and worry about something else like using synthetic blinker fluid.

duck wrote:2 - Current filter is paper.  Use it and worry about something else like using synthetic blinker fluid.

Oh no, not another blinker fluid thread!!!

In the last one you can see it as it was mounted from right side of the bike.

It looks fine to me.

Sent from Topic'it App

Put it back in.  Make a mental note to look at it again in 5 years or 80,000 km.

Point-Seven-five wrote:Put it back in.  Make a mental note to look at it again in 5 years or 80,000 km.

Hahaha! All right!

Sent from Topic'it App

George_Pap wrote:


In the last one you can see it as it was mounted from right side of the bike.

I hope it's not like that.....the side that is shown in the last picture should
point to the rear of the bike.

I wonder which filter your mechanic lubed.....

My mistake, during the upload Inge, the previous photo shows the visible side of the filter.
As for the mechanic.. I m actually glad for the final outcome. If it wasn't him i wouldn't have learn all these about my bike!
I feel much more confident now about it's operation and state , sure, I need to learn a lot more in the future but it feels great to know the most about your bike, especially if it's a granny like my K .

Sent from Topic'it App