R50 Carb/Intake Centering Bushings

[jposig]

I just got my carbs back from Charlie and though I haven't installed them yet they look beautiful. A nice touch is the return of all of the old parts that were replaced, obvious there are some really good upgrades on the original '58 carbs.

Question: I felt what is termed as centering bushings in the intake manifold on the motor side of the heat isolators. Why are they there and what do they do? Typically intakes are made bigger for performance and I've never seen this before on any of my bikes or cars.

I can't thank this group enough for the referral. Money and time well spent...

Jim

 

[20774]

Jim -

I'm not familiar with those terms. Can you provide some diagrams such as something on an online parts program for reference? Maybe RealOEM or from Salis Parts:

https://www.bmwclassicmotorcycles.com/parts/parts/

 

[jposig]

Jim -

I'm not familiar with those terms. Can you provide some diagrams such as something on an online parts program for reference? Maybe RealOEM or from Salis Parts:

https://www.bmwclassicmotorcycles.com/parts/parts/

I have the original silver parts book which called the part that name. Then I followed your provided link. Go to the R50 section. Then go to the carb diagram and you'll see the part in front of the heat isolator/gasket. They also call it a centering bushing. Part number is 11 61 0 043 168.

Thank you for your time......

 

[kinterridge]

They might be the 13 11 0 042 146. It's a dense material, split longitudinally, to slide inside, on the flanged side of the carb. I always just assumed, and may very well be wrong, that it was for the differing expansion rates between the carb and engine.

 

[20774]

Jim -

OK, I was sort of thinking that was it. I can't say as I've ever questioned the part. I recall seeing it on my R69S carbs. My thoughts are there's a lip on the inside of the carb on the outlet side so the item might fit in there...just from memory. The carb is isolated from the head by the thick gasket and this part fits inside there as well. My thought is that this helps to keep any heat away from the thick gasket. Although there is cool fuel-air rushing by this, it is bolted to the head so there's going to be heat trying to work backwards. I don't consider this part as a centering item, although I guess it might do that. But I think it also helps to keep the fuel-air flow as smooth as possible as it passes the discontinuities...the part just makes a smooth transition into the head.

Number 44 for those following along!

https://www.bmwclassicmotorcycles.com/parts/all-parts/carburetor/

As an update...I was looking at the part number. It seems that this part number only applies to the R50S and R69S...maybe the R69. On RealOEM, the part is not listed in the table for an R50 or R50/2. Note that the carb throat diameter for the R50 and R50/2 is 24mm whereas for the R69S it's 26mm.

 

[jposig]

Jim -

OK, I was sort of thinking that was it. I can't say as I've ever questioned the part. I recall seeing it on my R69S carbs. My thoughts are there's a lip on the inside of the carb on the outlet side so the item might fit in there...just from memory. The carb is isolated from the head by the thick gasket and this part fits inside there as well. My thought is that this helps to keep any heat away from the thick gasket. Although there is cool fuel-air rushing by this, it is bolted to the head so there's going to be heat trying to work backwards. I don't consider this part as a centering item, although I guess it might do that. But I think it also helps to keep the fuel-air flow as smooth as possible as it passes the discontinuities...the part just makes a smooth transition into the head.

Number 44 for those following along!

https://www.bmwclassicmotorcycles.com/parts/all-parts/carburetor/

As an update...I was looking at the part number. It seems that this part number only applies to the R50S and R69S...maybe the R69. On RealOEM, the part is not listed in the table for an R50 or R50/2. Note that the carb throat diameter for the R50 and R50/2 is 24mm whereas for the R69S it's 26mm.

I was curious because I don't have them. And I too looked at realoem.com and the part is ghosted for my application. It looks like someone might have done some port work to match the heat isolators/gaskets on my motor, a good thing.

Thanks to all of you for your time and continued education and support!!!

Jim