This R80ST came with no right exhaust header or collector box. I decided to replace the entire exhaust system as the rear muffler and left header had a fair amount of rust.

Tools

I use the BMW exhaust nut wrench. But, you can also get one from Euro MotoElectrics, as shown in the second picture below.

Parts

With exception of the rear muffler, I got all of the exhaust parts from Euro MotoElectrics at no cost as they have graciously agreed to support my goal of auctioning this bike and donating all the proceeds to the Motorcycle Relief Project.  that I got the rear muffler from Keihan Systems in the UK, but it is for the R80 G/S not the R80ST, but it fits on the ST using an adaptor they provide.

Part #	Description	Qty
18 11 1 451 843	EXHAUST PIPE CHROME LEFT	1
18 11 1 451 844	EXHAUST PIPE CHROME RIGHT	1
18 12 1 242 966	FRONT MUFFLER CHROME	1
18 12 1 242 965	REAR MUFFLER, Stainless Steel, R80 G/S	1
18 21 2 301 625	MUFFLER CLAMP, Header to Front Muffler	2
18 21 2 301 577	MUFFLER CLAMP, Rear to Front Muffler	1
46 63 1 451 460	COVER, Exhaust Shield Over Silencer	1
18 21 1 234 721	NUT, Header to Heads	2
18 21 1 230 585	COMPRESSION RING	2
18 21 1 230 586	CLAMP RING	2

The pictures below show the main components of the exhaust system and how they go together.

In the picture above, top-to-bottom, left-to-right, are the exhaust header nuts that attach to the threaded exhaust port, the collector box muffler clamp, the exhaust header clamping rings and the collector box exhaust header clamps.

Video

This is a short video summary of how I install the exhaust system.

VIDEO: 1983 BMW R80ST Install Exhaust System

Install Rear Muffler

I start by installing the rear muffler on the rear sub-frame. It mounts with a bolt, two flat washers, a wave washer and nut at the top. It mounts on the bottom rear sub-frame bolt at the bottom. I leave the bolts loose so I can adjust the muffler as necessary as I install the collector box and exhaust headers.

Attach Collector Box

There are clamps for the muffler and the header pipes that attach them to the collector box. I install the collector box on the end of the muffler and loosely attach the clamp to hold it on, but allow the collector box to rotate and move on the end of the muffler.

Install Header Pipes

Before I install the header pipes, I put anti-seize on the threads of the exhaust ports to make it easier to remove the header nuts and so the aluminum threads won’t gall.

The exhaust header pipe is clamped using two clamping rings. One is solid with a flat face and beveled face. It goes inside the header nut with the flat face of the clamp against the flat face of the nut. The second clamping ring has a split and has a flat face and a beveled face. The beveled face goes against the bevel face of the solid clamping ring. As the exhaust header nut is tightened, the split clamping ring compresses around the exhaust header pipe sealing it.

There is very little clearance on the left side header between the engine block and the rear of the side stand bracket. I use a bungee cord to extend the side stand to make it easier to install the left header pipe.

I insert the end of the exhaust header into the end of the collector box. Then I put the exhaust header nut on the other end of the header pipe and insert that end into the exhaust port and loosely tighten the header nut to hold the pipe in place. I repeat this on the right side pipe.

After getting both header pipes attached to the collector box and the exhaust ports I found it hard to get the header pipes to slide all the way inside the header ports and the collector box. So I used a 2×4 a shop rag wrapped around the header pipe and a plastic mallet and alternately tapped the exhaust headers into the exhaust ports until the larger diameter end of the exhaust header was fully inside the header nut.

Then I used the exhaust nut wrench to tighten the header nuts and then I tighten the collector box exhaust header clamps. I leave the muffler clamp loose until I mount the heat shield and side cover so I can get them aligned correctly.

Here is the routing of the left and right exhaust headers.

Install Left Rear Foot Peg

The left rear footpeg mounts in a hole of a bracket under the muffler. The red tape on the bolts means I haven’t tightened them yet so I can align the muffler, heat shield and  side cover.

Muffler Heat Shield

I’m going to wait to attach the R80ST muffler heat shield until I get the side panels back from the painter.

Since the muffler is for an R80 G/S, it does not have the imbedded nuts in the side of the muffler for attaching the heat shield. Keihan supplies an adapter kit to mount the heat shield as shown below.

The bracket attaches to the lower muffler mounting bolt and I have to drill holes in the heat shield for the mounting bolts. So I want to align the muffler and heat shield with the left side panel before I drill the holes so the heat shield and side panel are aligned.

What All Done Looks Like

Here is the new exhaust system installed.