Putting the mufflers on this bike is exhausting. [laugh track]. Okay, I just couldn’t resist that one.

I decided to replace the exhaust system due to the amount of corrosion I found on the original one. This year/model bike has two cross-over pipes while the earlier year airheads (before the 1981 model year, or before 09/1980) had a single cross-over pipe beneath the front engine cover. BMW added the second cross-over pipe to improve low end torque and reduce exhaust noise compared to the single cross-over pipe models.

I also install the Brown’s side stand that came with the bike as it attaches to the left side header bracket and the front hole of the side stand bracket uses special bolt and nut supplied with the side stand. There is also a toothed washer for the rear hole that mounts on the rear engine stud with the standard nut to keep the side stand bracket from rotating on the engine stud.

Tools

I use a special wrench from BMW (part # 83 30 0 401 758) to tighten the large aluminum nuts that secure the header pipes on the threaded exhaust spigots in the heads.

There are other sources for similar tools, for example Euro Motoelectrics has a tool.

Parts

I got the exhaust system from Euro MotoElectrics. The EME part numbers are shown in [ ] and link to the part description. They bundle several BMW exhaust parts into a single EME part number.

Part #	Description	Qty
18 11 1 337 149 [XManifold149]	EXHAUST PIPE LEFT – D=38 (from 09/80)	1
18 11 1 337 150 [XManifold149]	EXHAUST PIPE, RIGHT – D=38 (from 09/80)	1
18 11 1 337 152 [XManifold149]	CROSSOVER – BACK (from 09/80)	1
18 11 1 230 638 [XManifold149]	CROSSOVER (from 09/80)	1
18 12 1 233 210 [EXSilencer210EDL]	MUFFLER, LEFT – D=38 (from 09/80)	1
18 12 1 233 211 [EXSilencer210EDL]	MUFFLER, RIGHT – D=38 (from 09/80)	1
18 21 1 230 432 [Included]	PIPE CLAMP RIGHT (from 09/80)	1
18 21 2 302 071 [Included]	PIPE CLAMP LEFT (from 09/80)	1
18 21 1 336 553 [Included]	MUFFLER CLAMP – D=40 (from 09/80)	2

Video

A short video of the installation is below.

VIDEO: 1983 BMW R100RS Install Exhaust System

Install Headers and Cross-Over Pipes

The pictures below show the header and two cross-over pipes–the front and rear cross-over pipes are different lengths–and the mounting hardware.

Clean & Polish Exhaust Header Nuts

I use my parts tumbler with corn cob abrasive to polish the exhaust header nuts and the Brown’s side stand hardware.

Before I tumble them for 24 hours, I clean them in my carburetor cleaning dip can and scrub them with a tooth brush to remove the oil and grime. Here is how they turned out.

I used some AutoSol metal polish to finish them up. They look almost new again.

Test Fit Cross-Over Pipes And Mufflers

Before I assemble the exhaust system, I test fit all the pipes and mufflers. I found that the ends of the left header stubs that slide onto the cross-over pipes were raised. I used my Dremel tool with a grinding stone to grind down the edges until the cross-over pipes slide on easily.

The mufflers have an insert that swedges the diameter down from 40 mm to 38 mm. The earlier models of the RS had a 40 mm header pipe but later years, like mine, have 38 mm headers. The mufflers are designed to fit on both diameter header pipes. The inserts were tight but after I got them to go on the headers and after I rotated the mufflers back and forth on the headers, the mufflers slide onto the headers easily.

Install Header Pipes and Exhaust Nuts

The header pipe slides into the threaded exhaust spigot in the head. To secure it, two steel sealing rings are installed inside the header nut.

The large sealing ring has a flat face, a square shoulder and a bevel on the other face. The small sealing ring has a small flat face, a bevel face and is split.

The large sealing ring bevel face mates with the small sealing ring bevel face. The large ring fits inside the header nut with the flat face against the shoulder of the nut and the bevel face pointing outward. The smaller sealing ring fits on top of the  larger ring with the bevel faces mating. When the nut is tightened on the threads of the exhaust spigot, the smaller sealing ring compresses closing the split to seal the header pipe preventing exhaust gas from leaking.

Before I install the exhaust header nut with the sealing rings on the header screw it on the threaded exhaust spigot, I put grey anti-seize on the threads of the spigot to prevent the aluminum nut from galling on the aluminum threads of the spigot. Then I finger tighten the nut. I want the pipe to rotate in the spigot so I can align the header with the cross-over pipes, mounting brackets and muffler.

Slide On Cross Over Pipes

After I have both header pipes installed loosely in the exhaust spigots, I install the front and rear cross-over pipes. I push the cross-over pipe all the way onto the stub pipe on the right header. I rotate the left exhaust header and align the front and rear stubs with the cross-over pipes and then slide the cross-over pipes onto the left stubs until the cross-over pipes are about centered on the right and left stubs.

Before I finger tighten the stainless steel Allen bolt with the wave washer and nut that comes with the EME header pipe kit, I put some anti-seize on the treads to prevent galling. I orient the Allen heads to the front and finger tighten the nuts so I can adjust the header pipes as needed to mount the mufflers.

NOTE:
I learned later when installing the center stand the the orientation of the rear cross-over pinch bolts matters. The picture below is how I originally installed the cross-over pipe with the pinch bolts at the bottom like I oriented them on the front cross-over pipe, but the left one interfered with the center stand and return spring. I oriented the pinch bolts vertically, as shown in the second picture and that worked.

Install Header Brackets

The header brackets are handed and stamped with “L” and “R”. I install them on the header pipes by expanding the header brackets so they will slide around the headers.

Install Left Header Bracket And Brown’s Side Stand

The left header hangs off the front hole of the Brown’s side stand bracket and is secured with the special side stand hardware. I start by mounting the side stand bracket rear hole over the rear engine mounting stud. There is a star washer that helps keep the bracket from rotating. I install it against the bracket and under the flat washer. I finger tighten the nut while orienting the side stand bracket so the front hole is aligned with the header bracket to make it easier to install.

I use vice grips to compress the legs of the header clamp enough that I can install the bolt and tighten it a couple turns into the special nut.

The Brown’s side stand works very well with this bike as it’s not hidden by the cylinder and fairing unlike the stock BMW side stand. And you have to fish for the tab on the BMW side stand which is under the cylinder to retract the stand which is inconvenient.

The right side header bracket fits on the rear engine mount stud. I remove the nut and flat washer and slide the legs of the bracket over the stud. I use the vice grips to tighten the legs of the bracket enough to install the wave washer and nut on the stud. I finger tighten the nut so I can adjust the header pipe when I mount the muffler.

Install Mufflers

The mufflers are handed. The mounting brackets are welded on these mufflers.

The mufflers are secured onto the header pipe with clamps that slide over the end of the header pipe.

NOTE:
It is easier to install the mufflers if you remove the rear foot pegs.

I slide the mufflers onto the header pipes and then align the holes in the muffler brackets to line up with the holes in the rear foot peg bracket on the frame where the mufflers mount. The mufflers are secured to the bracket from the bottom with two Allen bolts that screw into threaded holes in the frame bracket with a large flat washer and wave washer. I tighten the Allen bolts to secure the rear of the mufflers to the frame.

NOTE:
The right side frame bracket also has the rear disk brake master cylinder bracket. The master cylinder bracket goes against the frame bracket and the muffler bracket goes against the master cylinder bracket.

When I have both mufflers mounted on the frame brackets I align the muffler clamps so they cover the seam between the muffler and exhaust header with the bolts on the bottom. I like them oriented that way so the clamp appears to be a smooth band around the muffler and header from the normal viewing angle. I tighten the bolts.

Adjusting Brown’s Side Stand

When I got the mufflers installed I noticed that when the Brown’s side stand retracted the foot of the stand contacted the left muffler. I need to adjust how far the side stand foot retracts. I thought about this for a bit and then came up with the idea of putting an M6 flat washer inside the clevis of the side stand bracket under the pivot. It turned out that the pivot captures the washer and clamps it against the curved pivot both when the side stand is retracted and when it is extended. So I didn’t have to glue it in place.

Tighten All The Fasteners

Now that all the pieces are installed, I tighten up all the fasteners starting from the rear muffler bracket. I go down one side and then other ending at the exhaust header nuts. I use a special wrench to tighten the large aluminum header pipe nuts that secure the header pipes into the head.  I lean on the handle to get the nut tight, but I don’t overdo it.

What Done Looks Like

Here is the new exhaust system. It looks very nice.

Revisions

2020-08-20  Clarification about the effect of the second cross-over pipe.
2020-08-22  Changed orientation of rear cross-over pipe to avoid center stand.