18 BMW 1983 R100RS Remove Exhaust System

Tools

I use a special tool to remove the exhaust header nut from the head. This is the BMW tool, (part # 83 30 0 401 758).

BMW Exhaust Header Nut Tool

BMW Exhaust Header Nut Tool

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

Euro Motoelectrics Exhaust Nut Tool

Euro Motoelectrics Exhaust Nut Tool

Exhaust System Mounting Overview

The exhaust system is secured to the engine with a large threaded nut on the header pipe that threads into the exhaust port of the header,

Aluminum Header Nut Screws Onto The Exhaust Port of the Head

Aluminum Header Nut Screws Onto The Exhaust Port of the Head

a bracket on the rear engine mount,

Right Header Pipe Bracket Showing How It Mounts to Rear Engine Mount

Right Header Pipe Bracket Showing How It Mounts to Rear Engine Mount

and by a two Allan bolts into the underside of each muffler bracket at the rear bottom of the frame.

Muffler Bracket Mounts to Underside of Frame Muffler Bracket

Muffler Bracket Mounts to Underside of Frame Muffler Bracket

Remove Mufflers

I remove the mufflers from the header pipe by loosening the clamp where the header pipe joins the muffler and then I remove the two Allan bolts on the underside of each muffler that secure the muffler to the frame muffler bracket.

Muffler-to-Header Clamp

Muffler-to-Header Clamp

Muffler-to-Header Clamp Detail

Muffler-to-Header Clamp Detail

Header-to-Muffler Clamp-40 mm

Header-to-Muffler Clamp-40 mm

Remove Muffler From Frame Muffler Bracket

Remove Muffler From Frame Muffler Bracket

Muffler Bracket Mounting Hardware Detail

Muffler Bracket Mounting Hardware Detail

Then I slide the muffler off the header pipe by rotating it back and forth while pulling it to the rear. On the bottom of the muffler an “L” shaped mounting bracket is bolted on and it the bracket that is secured to the frame muffler bracket by the Allan bolts.

Muffler "L" Shape Mounting Bracket Detail

Muffler “L” Shape Mounting Bracket Detail

Unfortunately, the mufflers are rusty, and one of them has rusted through where it mounts to the header pipe.

Muffler Corrosion

Muffler Corrosion

Muffler Corrosion

Muffler Corrosion

Remove Header Pipes

This bike has a Brown side stand on the left side. Consequently the left header hanger is relocated from the rear engine mount and moved forward to the front of the side stand bracket.

Left Header Pipe Bracket Attached To Front of Brown Side Stand Bracket

Left Header Pipe Bracket Attached To Front of Brown Side Stand Bracket

The header hanger is secured to the hole in the Brown side stand bracket with it’s own bolt and thin faced shoulder nut and I remove it.

Brown Side Stand Supplied Shoulder Nut Detail

Brown Side Stand Supplied Shoulder Nut Detail

Brown Side Stand Supplied Header Bracket Hardware Detail

Brown Side Stand Supplied Header Bracket Hardware Detail

The header brackets are bent so the tabs have an off-set to the inside. This allows them to mount flush to the frame, or in the case of a Brown side stand, flush to the side stand bracket as shown below.

Left Header Pipe Bracket Detail

Left Header Pipe Bracket Detail

The right side header hanger bracket is mounted on the rear engine stud, and I remove it.

Right Header Pipe Bracket Mounts to Rear Engine Mount

Right Header Pipe Bracket Mounts to Rear Engine Mount

Header Pipe Bracket Hardware Detail

Header Pipe Bracket Hardware Detail

There is an extra spacer between the frame and the inside of the bracket that I do not believe is stock.

Header Pipe Hardware Detail-Extra Washer That Is Not Stock

Header Pipe Hardware Detail-Extra Washer That Is Not Stock

Each of the exhaust header hanger brackets is stamped with “R”ight or “L”eft as they fit on one side or the other.

Header Pipe Brackets Are "Sided" and Marked For Side

Header Pipe Brackets Are “Sided” and Marked For Side

Remove Exhaust Header Nut

I use a special BMW tool to remove the exhaust header nut. I insert the tool firmly between the fins of the nut being sure to seat the fins of the wrench as far into the fins of the nut as I can so I won’t break a fin on the nut as I remove it.

Remove Exhaust Header Nut

Loosen Exhaust Header Nut with Special Tool

I lean on the exhaust nut tool and mine turns easily. But, if it won’t move easily, I use a small maul (2 to 5 Lb sledge hammer) and hit the end of the tool handle sharply. When it budges, I loosen the nut with the tool a bit more.

When the nut seems easy to turn with the tool I remove it and slowly turn the nut by hand until it comes loose.

Remove Exhaust Header Nut Slowly by Hand

Remove Exhaust Header Nut Slowly by Hand

WARNING:
The steel exhaust port threads in the head can be rusted, coated with carbon. Therefore, when removing the nut, you can gall the aluminum threads of the header nut and damage the steel threads in the exhaust port of the head. If you do that, it’s a bad day. 🙁

So, some caution is advised when removing the nut. You should be able to break the nut free with out too much force. If it’s not moving, try a small sledge (2-5 Lb) on the end of the tool’s handle to see it will break free. If it doesn’t seem to move after several sharp blows, assume the aluminum header nut is stuck on the port threads and trying more force will gall the threads. In that case read the following from Bob Fleischer’s site for methods to remove the nut and not damage the exhaust port threads.

–> Exhaust Pipe Finned Nuts

When you break the nut free with the wrench, slowly loosen it by hand. If at any time it starts to get hard to turn STOP. The aluminum threads are starting to gall. Tighten it a bit until it turns more easily. Heat the aluminum nut quickly with a propane torch for a minute or two, and then try again. If it binds up again, see the above link for methods to remove the nut and not damage the exhaust port threads.

When the nut is off, you can see the two metal rings that fit around the header pipe to seal it to the head. There orientation is shown in the pictures below.

I leave the cross-over pipe in place and remove the exhaust header. I use a rubber mallet to tap on the inside bend of the header, alternating between sides, to coax it out of the exhaust ports in the head.

Tapping Header Pipe With Rubber Mallet To Help Slide It Out

Tapping Header Pipe With Rubber Mallet To Help Slide It Out

NOTE:
I took the above staged picture to show how to use the rubber mallet to help move the header out of the head. It was a posed shot and I failed to remove the exhaust header nut as you should do before tapping on the inside curve of the header. So, remove that nut, then tap, but not so hard you dent the header pipe 🙂

My header pipes slide out of the exhaust ports in the heads after a number of taps and several wiggles of the header assembly as I pulled on them.

Headers Pulled Out Of Heads

Headers Pulled Out Of Heads

Header Pipe Assembly Removed

Header Pipe Assembly Removed

Header Pipe Seal Rings Orientation

Here is more detail about the exhaust header pipe sealing rings and their orientation on the pipe and inside the aluminum header nut.

Header Sealing Rings Detail

Header Sealing Rings Detail

Header Sealing Rings Detail

Header Sealing Rings Detail

Header Sealing Rings Orientation Detail

Header Sealing Rings Orientation Detail

Header Nut & Sealing Rings Orientation Detail

Header Nut & Sealing Rings Orientation Detail

The headers have quite a bit of rust.

Header Pipe Corrosion

Header Pipe Corrosion

Header Pipe Corrosion

Header Pipe Corrosion

I remove the cross-over pipe by removing the Allan pinch bolts at the bottom of the cross-over pipe. However, mine is missing one of the Allan bolts.

Header Cross-over Pipe Pinch Bolt

Header Cross-over Pipe Pinch Bolt

Header Cross-over Pipe Hardware Detail

Header Cross-over Pipe Hardware Detail

Header Pipe Components

Header Pipe Components

Header Pipe Diameter

There are two size header pipes on the RS bike, 38 mm and 40 mm. But by 1983, all the header pipes are the smaller 38 mm size. But on the 1977 and 1978 RS bikes, you could have either size header pipe depending on if your engine was stock, or the “CFO” version. California, Florida and Oregon had state rules for emissions that required a smaller header, among other changes. Usually your engine block with be stamped with “CFO” near the VIN number stamp by the oil dip stick. But, it’s always possible some previous owner changed the heads on your bike and you may not have the header pipes you would expect.

As I expected, these pipes are 38 mm, and that is confirmed by the size stamped on the header-to-muffler bracket that is “40 mm”, or 2 mm larger than the header pipe diameter. If you wonder if your bike has the larger diameter header pipe, look at the header-to-muffler brackets, and if you see “42 mm”, you have the larger diameter 40 mm headers and heads with 40 mm exhaust ports.

Header Pipe Diameter-38 mm

Header Pipe Diameter-38 mm

Header-to-Muffler Clamp Diameter-40 mm

Header-to-Muffler Clamp Diameter-40 mm

2 thoughts on “18 BMW 1983 R100RS Remove Exhaust System

    • Hi Anthony,

      Yes, if the nut gets tight and you can’t make progress with the techniques Bob suggests, split the nut. That said, the less violence the better. 🙂

      Best.
      Brook.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.