Earlier, when I first got the bike, I rebuilt the carburetors and removed the “Pulse Air” system from the air box. You can read about how I did that here.
- 13 BMW 1983 R100RS Rebuild Bing 94/40 Carburetors & Karcoma Petcocks
- 13 BMW 1983 R100RS Update Pulse Air System and Replace Oil Breather Hose
The following includes similar information to what’s in the documents above, but here I’ve simplified it to just removing these components.
The carburetors are easy to remove. They are attached to the air box air intake and the cylinder intake spigot using “hose clamp” like straps. I use a flat blade screw driver to loosen the clamps.
The air intake rubber bushing attaches to an aluminum bushing in the air box. I push the rubber bushing down the air tube to get it off the air box bushing and remove the air intake from the carburetor.
There is a steel bushing inside the air box end of the plastic air intake tube.
I mark the air intakes to make it easier to get the right one on the correct carburetor.
Here are the air intake parts.
I pull the carburetor off the cylinder intake bushing and remove the bushing from the intake spigot. I also remove the fuel lines from the metal tee.
Remove Choke & Throttle Cables From Carburetor
The Bing carburetor on the 1983 RS uses a return spring for the choke since the choke lever is attached to the handlebar and uses a flexible braided steel cable. The earlier style choke used solid wire with a lever on the left half of the clam shell cover of the air box.
I remove the return spring so I can easily rotate the choke lever to remove the cable ferrule from the slot in the choke arm. Then I reattach the return spring.
I loosen the lock nut and unscrew the choke cable adjuster from the top of the carburetor.
The procedure is similar to remove the throttle cable.
Choke & Throttle Bowden Cable Details
Both the choke and throttle cables on the 1983 model use a Bowden cable system. There is a single cable that goes from the right handlebar throttle mechanism to a cable splitter mechanism under the gas tank. The other end if the splitter mechanism has two cables that go to either each choke lever, or throttle plate lever, on the carburetors. Therefore, a single handlebar cable pulls two cables going to the carburetors. These cables look the same, but the part numbers printed on the sheath show they are not. I put a label cable so I won’t get them confused when it’s time to put things back together. You can see the internals of the Bowden cable splitter here:
Since I am converting this bike to an RT model, I will have to replace the handlebar cables for the throttle and choke since they are longer on the RT model than the RS model due to the wider RT handlebar.
Here is the carburetor stripped of the fuel line and cables.
Remove Air Box
The yellow pipe inside the bushing in the air box is part of the engine crankcase vent system. It distributes vapors from the oil pan to both carburetors. I remove the bushing by pulling it out of the sleeve in the airbox.
I remove the cover with the intake snorkels from the air box by releasing the metal clamps that secure the cover to the air box body.
Remove Intake Tunnels and Crankcase Breather Hoses
Inside the air box are the intake tunnels with the hoses for the engine crankcase breather that feeds crankcase vapor into each carburetor. On the earlier models with the clam shell air filter housing with the cylindrical air filter, there was one crankcase breather hose that fed only the right carburetor air intake tube.
Earlier, I removed the solenoids and the piping to the exhaust passages in the cylinders that is part of what BMW called the “Pulse Air System”. You can read about how I did that here.
The crankcase breather hose comes into a tee fitting inside the air box with a wire clip to secure it. I slide the clips down the breather hose to remove the hose from the tee and then remove the intake tunnels by pushing them back into the air box.
Inside the intake tunnel is a plastic vent pipe that delivers the crankcase vapor into the carburetor intake tube.
The rubber breather hose presses into the intake tunnel. If you remove the hose, you can pull the plastic vent pipe off the breather hose.
I mark the intake tunnels so I will easily know which side they go to.
I remove the breather hose tee. It fits into the breather hose inside the top engine cover that goes to the crankcase breather valve assembly.
The air box is secured to the top of the transmission with two bolts and one nut. The left bolt and right nut secure the transmission to the engine. The middle bolt was used to secure the bottom strap for the older style clam shell halves, and is reused to secure the new style air box. I remove the bolts and the nut.
The breather hose from the crankcase breather valve has a grommet that the tee fit into. I push the grommet out of the hole in the air box, so I can slide the air box to the rear and lift it off the top of the transmission.
2019-11-22 Edits and typos.
Hello, I am restoring a 1982 R100RS and in the process of removing the airbox i discovered the middle bolt is missing. I noticed oil in the airbox and suspect that it is pulling oil through the bolt hole, or at least i hope so. What is the bolt size please so i can replace it?
I’d use MAX BMW’s parts fiche to figure out what I need to order.
Where can I get the air breather hoses that are connected to the crankcase breather tee?
Any BMW Motorcycle dealer can order parts for you.
Reinstalling this airbox is proving to be most difficult. I removed everything to renew the fuel lines and I’ve had to unbolt the airbox again to try and manipulate the air intake tubes into place. Now I can only get one bolt in (right side) The air intakes would not install with airbox in place. Is there a special technique? For something so agricultural there is very little play to allow for movement
I show how to install the airbox and air intake tubes here:
13 BMW 1983 R100RS Install Carburetors, Cables and Air Box
I hope that helps.
Many thanks for the reply and link. The process became so simple when I studied your instructions. Thank you Brook
You’re Welcome. I’m pleased it finally all came together for you 🙂