Returning Air Intake on a 2004 R1150R To Stock - Need Advice

I'm a new owner of a 2004 R1150R that the previous owner modified by putting K&N air filters on the throttle housing assembly on each side. I am in the process of restoring it to the stock configuration, working with the internal air filter.

The original left and right intake manifolds were sawed off on the end that would normally connect to the throttle housing. Whoever did the modification simply just stuck the manifolds back into the air cleaner housing and called it a day. I looked at the diagram and already ordered the manifolds, but what I am having a difficult time determining whether there is an additional rubber gromet needed to connect the manifolds to on the air cleaner housing side. In the diagram on this site it is #6.

http://www.2wheelpros.com/oem-parts/2000-2006-bmw-r1150r-r28-suction-silencer-filter-cartridge-assembly.html?partnum=13711341405

Judging by the sawed of manifolds, it looks like they are too small and leave a gap where they would connect to the air cleaner housing.

Could someone post a picture of their manifolds connecting to the cleaner housing, or confirm by looking at the diagram whether that rubber gromet is also needed? I appreciate any input!

Yes there is a rubber grommet that seals them to the airbox and it is inserted from the inside.

You can see it here on the 1150R fiche at MaxBMW.
It is number 6 in this drawing:

https://shop.maxbmw.com/fiche/DiagramsMid/B0002887.png?v=07242017

PS: Getting rid of those K&N filters is a good idea. They let in a lot more dirt than paper filters due and also alter the airflow into the throttle bodies. Unless you are building a race bike and altering a lot of what BMW designed in I would not mess with how they designed the air intake. They did things for a reason. Look at how different the tubes are on a G/S to an RT for example. This is not a mistake, it's by design.

That's the same diagram I found on the other website and it looks like it is numbered the same, #6. I figured that there must be another part that the manifold is attached to, but the diagram is a bit confusing.

After posting the original question, the mail actually just delivered the Clymer Manual for the R series I ordered. In it that part is called "Inlet Pipe", but it uses the same diagram as in the fiche, just numbered differently. I guess I'll pop open the cleaner housing and see if the previous owner just shoved it back into the housing like the manifolds. If it's not there I'll also order it.

Thanks for confirming!

I know when I worked on mine shoving them into the airbox was way easier than pulling them out. A quick spray of rubbing alcohol made the tubes slide nicely though. I would not be surprised if they are shove up in there. There is a lot more room than I thought there would be.

I think I have the mystery solved. The replacement parts are not here yet, so finding pictures on the Internet helped figure out what's there and what is not.

The rubber gromet is a seal that sits in the opening of the air cleaner house, essentially just a ring to make the seal. The diagram doesn't really show accurately what those parts look like, including that rubber seal. In my case, it's there, so that's good.

Next, comparing the picture I found and what was left of the manifolds stuck in the housing now makes sense. The previous owner sawed off one part of the manifold where indicated in the picture. Again, the diagram is misleading, as it does not show the shape of the entire manifold.

So, all that to say that what's in the mail should fix the issue of returning the air intake back to stock.

Hopefully you ordered replacement grommets where the air tubes met the air box. I would suspect they might need replacing, maybe not. Realize if they leak you will be drawing unfiltered air into the intake.

Speaking of intakes I have seen someone replacing only the intake tubes on an RS with GS tubes claiming performance increase. Anyone has any knowledge if this can be true?

tibork said:

Speaking of intakes I have seen someone replacing only the intake tubes on an RS with GS tubes claiming performance increase. Anyone has any knowledge if this can be true?

Click to expand...

A lot of us did this in the early Oilhead days after some serious experimenting by Rob Lentini. The GS tubes are in their center smaller diameter than the RS or RT tubes. This increases the velocity of the airflow through the tubes and alters performance characteristics. The change provides stronger low end and mid range torque - probably at the expense of top end horsepower. But from a driveability standpoint it seemed to be a reasonable improvement.

tibork said:

Speaking of intakes I have seen someone replacing only the intake tubes on an RS with GS tubes claiming performance increase. Anyone has any knowledge if this can be true?

Click to expand...

If true, what someone has a very sensitive posterior.

BC1100S said:

If true, what someone has a very sensitive posterior.

Click to expand...

Rob did a few dino tests. And some of us did posterior tests. It is the same function as altering throttle body diameters, or intake valve size, lift or timing. These alter mid-range vs top end dynamics. Pick your poison. Do you like responsiveness in traffic or top end? Your choice.

OK, so I have a sensitive posterior, nothing new there...
I swapped out the tubes on my '97 RT for the GS tubes, and I liked the change.
It improved the lower rpm range, and I have no idea if I lost any top end... I still pulled past the ton with more to spare... and I didn't bother playing with the Cat-Code plug.
https://ibmwr.org/index.php/2002/10/18/r1100rs-rt-tuning-improvements-with-gs-parts/

Haven't tried it on my 1150, tho... hmmm...

I wish someone has told me this before I went and spent $$ on a snorkel which eliminated the tight kink the original one had on my 1100S. Oh well, c'est la vie!