BMW K bikes (Bricks)

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1Back to top Go down   Air Box to Pod Filter Empty Air Box to Pod Filter on Wed Mar 20, 2019 8:05 pm

Fw66

Fw66
active member
active member
Hey All,
I'm currently in the process of building a 1990 BMW k75 street tracker for the 2019 Quail out here in the Bay.
I've made a lot of progress thanks to many of the members here on the forum!

I'm currently working on the air-box: 
I've cleaned up the back end of the bike and moved the battery to the bottom half of the air-box using an antigravity and a couple of custom printed fillers.
The disassembly of the air-box inspired me to explore different air filtering options. I've always loved the look of pod filters and have decided to go towards that route.

I've seen other builders use pod-filters and some sites are even making custom conversion brackets:
https://www.kickstartershop.de/en/product?info=9586&country_preselect_country=DE
https://cafe4racer.eu/en/air-filter-adpaters-bmw-k-100-k75-k1100/1775-bmw-k-serie-air-intake-stainless-90-reduction.html
These brackets attach directly onto the air sensor unit as shown in the pictures.

Questions for the forum:

  1. I've read online that people have done this conversion before and have not had to re-jet, can anyone confirm?
  2. Is air intake surface area crucial here? Or do I just need to ensure that air is funneled into the system without any blockages? Angles of the intake and number of pods are not important?
  3. What aftermarket pipes or methods can be used to make a custom air sensor to carb pipe? (The OEM elbow pipe isn't exactly the right angle)


Thanks in advance!

    

2Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Wed Mar 20, 2019 8:36 pm

robmack

robmack
Life time member
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K-bikes don't have carbs; they're fuel injected and have throttle bodies. So, you can't have an air sensor to carb pipe.

Are you thinking of deleting the plenum chamber?



Last edited by robmack on Wed Mar 20, 2019 9:44 pm; edited 1 time in total


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

3Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Wed Mar 20, 2019 9:31 pm

Two Wheels Better

Two Wheels Better
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Moderator
The Kickstarter link shows an intake which suggests retention of the critical AFM. Of course, there is nothing in the literal way of 're-jetting' can be done there. If it's wide open performance and a dash of 'look at me' you're after, that shiny metal bit is a viable option, but if you desire ridable tractabliity of power, the original airbox canna be beat.


__________________________________________________

1987 K100RS, '89 K100 w/K1100RS engine, '93 Framed K11/K12 engine 'Big Block', '96 K1100RS, '09 K1300GT, '13 R1200RT-P, '95 R100 Mystic & '77 R75/7.

    

4Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Wed Mar 20, 2019 9:49 pm

Laitch

Laitch
Life time member
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@Fw66 wrote:I've read online that people have done this conversion before and have not had to re-jet, can anyone confirm?
I know of a K75 that has 200K miles on it with a converter similar to the Kickstarter version you posted. It seems to work satisfactorily for its owner. There are no jets to re-jet for the reasons robmack indicated. There are other classic K motos where filter pods can be fitted to each throttle body but 2V motos like yours don't easily accommodate that modification.


__________________________________________________
1995 K75 73,000 miles
Air Box to Pod Filter Usa-lo10
    

5Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Thu Mar 21, 2019 1:41 pm

Fw66

Fw66
active member
active member
@robmack wrote:K-bikes don't have carbs; they're fuel injected and have throttle bodies. So, you can't have an air sensor to carb pipe.

Are you thinking of deleting the plenum chamber?

Thanks for the replies, I misspoke and called the plenum chamber the carb...

I am not getting rid of the plenum chamber, just need to find a way to pipe the plenum chamber to the AFM as the stock elbow pipe doesn't give me the best angle. Any ideas?

Lastly, does the shape of or volume dimension of the pod filter bracket matter? I assume the bracket will have to have a diameter as wide as the AFM hole but other than that there shouldn't be any other considerations right?

    

6Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Thu Mar 21, 2019 3:01 pm

chris846

chris846
Life time member
Life time member
You can trim the 90' rubber elbow that links the AFM to the plenum. I halved mine so's the AFM sits at a rakish 45' to the plenum. You might have to swap the large hose clips around, can't remember exactly, I'll check my K100 tomorrow.

There's a small cast ally flange on the intake side of the AFM which you can remove to leave a 4-bolt mounting and a square inlet hole. This gives you more possibilities viz the adaptor for the filter.

The AFM also has a couple of M6 threaded holes on the side which are unused. You can use these for a support bracket for the AFM - there's a couple of M8 tappings on the top of the crankcase nearby too.

Photos tomorrow, promise.


__________________________________________________
The Longest Lunch
    

7Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Fri Mar 22, 2019 2:04 pm

chris846

chris846
Life time member
Life time member
Not great photos, but here's the filter adaptor:
Air Box to Pod Filter 02710
And the bracket:
Air Box to Pod Filter 03210
And the shortened rubber elbow:
Air Box to Pod Filter 02910


__________________________________________________
The Longest Lunch
    

8Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Fri Mar 22, 2019 7:08 pm

Fw66

Fw66
active member
active member
Thanks for the photos! Super helpful.
I actually think I'm going to reuse the airbox and have a custom air intake coming out of it since I'm using the bottom half as a battery holder.
I'll post pics as the parts come together.

    

9Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Sat Mar 23, 2019 4:01 am

chris846

chris846
Life time member
Life time member
So you're going to seal off the bottom half of the airbox so's it can house the battery, and cut a hole in the top half for the inlet - with a cone filter attached to the outside?

Clever thinking, I like that. Must be a first.

A product called U-Pol Tiger Seal is just about the best thing for permanently bonding plastics/metal/anything together in these sort of applications. I'm thinking of the cone filter stub that you might have to graft onto the top half of the airbox, with all its curves.


__________________________________________________
The Longest Lunch
    

10Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Sun Mar 24, 2019 4:03 am

GF Wollongong

GF Wollongong
Gold member
Gold member
Thanks for the pics... am about to pick up bike without plenum but does have the AFM. Will probably weld up a version of your bracket.

Was amused to see you describe the angle of the pod attachment as "rakish" - the only other time I've seen that reference was in a Spike Milligan (possibly... Hitler: My Part in his Downfall) book - photo of his mate with his hat on a rakish angle. 

Must be a British thing! (My family were 10pound poms to Australia in 67... I was 2 and there was probably a 10pound pong in my nappy by the time we arrived)

The bike is in a sorry state but can't so no to another stray

GF

    

11Back to top Go down   Air Box to Pod Filter Empty Re: Air Box to Pod Filter on Mon Mar 25, 2019 8:30 pm

Fw66

Fw66
active member
active member
@chris846 wrote:So you're going to seal off the bottom half of the airbox so's it can house the battery, and cut a hole in the top half for the inlet - with a cone filter attached to the outside?

Clever thinking, I like that. Must be a first.

A product called U-Pol Tiger Seal is just about the best thing for permanently bonding plastics/metal/anything together in these sort of applications. I'm thinking of the cone filter stub that you might have to graft onto the top half of the airbox, with all its curves.

Yea exactly! I'm actually getting a guy to 3D print the piece that goes into the top half of the airbox...hoping it'll come out super clean.
IF it does, there will be 3 pod filters going horizontally across the airbox.

    

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