11 BMW 1983 R100RS Remove Flywheel & Rear Main Seal

I remove the flywheel so I can replace the rear crankshaft main seal and the oil pump cover o-ring. In order to get to the flywheel, I remove the transmission and the clutch as I show in these write-ups.

I removed the engine from the frame and put it on my large work bench since I am powder coating the frame. But this work can be done with the engine in the frame.

Engine Out of Frame On The Workbench

Engine Out of Frame On The Workbench

Tools

I use an impact wrench to remove the flywheel bolts. This makes it easy to remove them without having to immobilize the crankshaft to keep it from turning.

Impact Wrench with 19 mm Socket Removes Flywheel Bolts Easily

Impact Wrench with 19 mm Socket Removes Flywheel Bolts Easily

Rear Main Seal Removal Tool From Cycle Works

I use the Cycle Works rear main seal removal/installation tool to remove the rear main seal.

Cycle Works Rear Main Seal Tool

Cycle Works Rear Main Seal Removal/Installation Tool

Flywheel Guide Ring Removal Tool From Cycle Works

I got this tool a year or two ago. It looks like it’s no longer available from Cycle Works. It is used to pull the guide ring off the flywheel. This is useful if the ring is stuck on and heating it, as I did, fails to get it off. I show how to use the tool below.

Cycle Works Flywheel Hub Ring Puller Tool

Cycle Works Flywheel Hub Ring Puller Tool

Video

I shot a short video of highlights of the procedure used in this write-up.

Avoiding Disaster

Since I’m going to remove the flywheel after I remove the clutch, I need to avoid a disaster involving the crankshaft front thrust washer coming off it’s mounting pins. If that happens, I have to remove the crankshaft to get it back on the pins, which isn’t a disaster but a real PITA. Should I not notice that the thrust washer is off the pins and then tighten the flywheel bolts, there is a high likelihood of damaging the crankshaft and crushing the pins that are cast into the engine block, which is a true disaster.

The way to prevent the front thrust washer from coming off it’s mounting pins is to force the crankshaft to the rear so it butts up against the thrust washer. I do that by putting a short, 12 mm long, 6 mm Allan head bolt into the recess of the alternator rotor’s Allan head bolt that attaches the rotor to the crankshaft.

M6x12 Bolt For Pushing Crank Against Front Thrust Washer

M6x12 Bolt For Pushing Crankshaft Against Front Thrust Washer

M6x12 Allan Bolt Inserted Into Alternator Rotor Allan Bolt Recess

M6x12 Allan Bolt Inserted Into Alternator Rotor Allan Bolt Recess

Then I install the front engine cover using the two bolts and finger tighten them so they pull the front cover tight against the head of the 6 mm bolt.

WARNING:
DO NOT OVER TIGHTEN the two front cover bolts or you can damage the alternator rotor bolt and/or front engine cover. You just need to snug them up by hand. And, it you have the earlier model front cover with a third cover bolt at the bottom, you don’t need to install that bolt.

When the M6x12 bolt is correctly installed, there is a slight gap between the front cover and the engine block at the bottom of the cover. That gap is your sign you have safely pushed the crankshaft up against the front thrust washer and you can safely remove the flywheel.

Hand Tighten Front Engine Cover Bolts-DO NOT OVER TIGHTEN

Hand Tighten Front Engine Cover Bolts-DO NOT OVER TIGHTEN

Gap At Bottom of Front Cover Shows Cover is Firmly Against M6x12 Bolt and Crankshaft Is Against Front Thrust Washer

Gap At Bottom of Front Cover Shows Cover is Firmly Against the M6 Bolt

Secure Engine to Work Bench

I don’t have an engine stand, so I secure the engine to my work bench. I use a 2×4 under the front timing chest cover to keep the engine from tipping forward and I use two ratchet straps connected together to clamp the engine to my bench top by passing the strap under the bench and over the engine’s top cover so the engine won’t move around as I work on it.

Securing Engine to Work Bench with 2x4 Under Timing Chest Cover

Keeping Engine From Tipping Forward with 2×4 Under Timing Chest Cover

Securing Engine to Work Bench with Ratchet Strap

Securing Engine to Work Bench with Ratchet Straps

After I secure the engine block to my work bench it’s easy to see there has been some oil leaking out of the rear of the engine onto the shelf above the oil pan. So, something is leaking, either the rear main seal, the oil pump cover o-ring or the flywheel o-ring.

Signs of Oil Leaking From Rear of Engine

Signs of Oil Leaking From Rear of Engine

Set Crankshaft To Top Dead Center (TDC)

It’s important to set the crankshaft at TDC before removing the flywheel. I need to mark the flywheel and engine with index marks so when I install the flywheel again, it will be attached to the crankshaft in the correct orientation. I put some white paint next to a flywheel bolt and add a line on the engine block that aligns with that bolt.

WARNING:
If the flywheel is rotated by one crankshaft bolt hole from where it should be on the crankshaft, the crankshaft will be out of synch with the flywheel by 72 degrees and the ignition timing marks on the flywheel will be out of synch by 36 degrees since ignition timing is defined by the camshaft and the camshaft rotates at one-half the speed of the crank.

Flywheel and Crankshaft Set to TDC

Flywheel and Crankshaft Set to TDC

Flywheel & Engine Block Index Marks

Flywheel & Engine Block Index Marks

Remove Flywheel From Crankshaft

I use my impact wrench with a 19 mm socket to remove the flywheel bolts. This is a quick way to get them off since I don’t have to block the flywheel to keep it from turning.

Removing Flywheel Bolts with Impact Wrench

Removing Flywheel Bolts with Impact Wrench

Flywheel Bolts Coming Out

Flywheel Bolts Coming Out-Note Index Marks on Flywheel and Engine Block at 10:00 Position

With the bolts removed, I could see a little oil around the bolt holes. It likely is coming from a leaking flywheel o-ring.

Small Amount of Oil Next to Bolt Holes

Small Amount of Oil Next to Bolt Holes

I need to pull the flywheel off the rear crankshaft nose. I put three clutch bolts screwed into every other hole in the flywheel. Then I use my vice grips (you could use pliers but the vice grips were handy) to grab each clutch bolt and give it a tug and a wiggle. I work my way around the flywheel tugging and wiggling the three bolts. It took me two times around the flywheel to pull it free from the crankshaft.

Three Clutch Bolts Installed Symmetrically Help Me Pull The Flywheel Off The Crankshaft

Three Clutch Bolts Installed Symmetrically Help Me Pull The Flywheel Off The Crankshaft

Grabbing Clutch Bolt To Give A Tug

Grabbing Clutch Bolt To Give A Tug

Once I get the flywheel off, I put a paint mark next to the crankshaft bolt hole that aligned with the paint mark I put on the engine block when I added the index marks to the flywheel and engine block. I also decided to add a couple punch marks onto the face of the crankshaft nose and the flywheel hole so if the paint comes off when I clean the inside of the bell housing and the flywheel, I’ll know which crankshaft bolt hole to index the flywheel to.

Punch Marks Added to Crankshaft Near Marked Bolt Hole

Punch Marks Next To Flywheel Bolt Hole

Punch Marks Next To Flywheel Bolt Hole

The back of the flywheel has a guide ring that fits over the rear nose of the crankshaft. The older, spring loaded, sharp edged seal was not used in 1983. The older seal cuts a groove into the flywheel hub over time leading to oil leaks. Starting in the 1983 model year, a new teflon (PTFE) seal was used. The seal I have in the engine block is the new teflon one.

Newer Teflon (PTFE) Seal Was Installed

Newer Teflon (PTFE) Seal Was Introduced In The 1983 Model Year

You can see in the shiny band around the hub some grooves in the outside of the hub. The grooves are likely caused by clutch dust getting under the seal and acting as an abrasive.

Flywheel Sleeve Shows Some Grooves From the Rear Main Seal

Flywheel Guide Ring Shows Some Grooves From the Rear Main Seal

The front face of the flywheel has the BMW part number stamped on it.

Flywheel Has BMW Part Number Stamped On It

Flywheel Has BMW Part Number Stamped On It-Note The Nick On Edge Of Guide Ring Sleeve Next To The Bolt Holes

And, there is a paint mark on the flywheel teeth showing the heavy part of the flywheel. The clutch cover plate and pressure plate also have factory paint marks. When assembling the clutch on the flywheel, the heavy part of each component should be installed 120 degrees from each other. This ensures the engine is as balanced as possible which reduces engine vibration.

Remove Flywheel Guide Ring

The guide ring stayed on the flywheel and didn’t want to come off. The reason it didn’t want to come off was because the sleeve that fits into the flywheel hole was dented next to each of the flywheel bolts.

Dings In Perimeter of Sleeve Around Guide Ring Nipple From Impact Wrench

Dings In Perimeter of Sleeve Around Guide Ring Nipple From Impact Wrench

It occurs to me that when I used the air impact wrench, it nicked the edge of the guide ring sleeve. The sleeve is a bit proud of the flywheel face. The edge of a flywheel bolt is very close to the edge of the sleeve so the impact socket nicked the top of the sleeve.

I heated the front of the flywheel around the guide ring sleeve. Then I tapped on the nipple gently a couple times with my rubber mallet and it came loose.

Pinpoint Butane Torch

Pinpoint Butane Torch

Using Pinpoint Butane Torch To Heat Guide Ring

Using Pinpoint Butane Torch To Heat Around The Guide Ring Sleeve Next To Bolt Holes

Guide Ring Removed

Guide Ring Removed

Guide Ring Removed Showing Center Nipple and Sleeve

Guide Ring Removed Showing Center Nipple and Sleeve The Fits Into Hole In Flywheel

Flywheel with Guide Ring Removed

Rear Of Flywheel with Guide Ring Removed

Flywheel with Guide Ring Removed

Front Of Flywheel with Guide Ring Removed

I use a flat file to carefully dress the top of the sleeve and the indents on the perimeter of the sleeve to smooth them out. The guide ring now slides into and out of the flywheel center with just a gentle tap on the nipple.

Using Cycle Works Tool To Remove Guide Ring

The outer ring fits around the hub with the countersunk holes facing you. The holes align with the holes in the flywheel and crankshaft nose.

Cycle Works Outer Puller Ring

Cycle Works Outer Puller Ring

Puller Ring Fits Over Guide Ring

Puller Ring Fits Over Guide Ring

The nut is machined with a lip that will slide into the groove on the guide ring. I place it on top of the outer ring and then install the three puller screws into the outer ring. The puller bolts are smaller than the threaded holes in the crankshaft nose so they bottom out in the holes. I use needle nose pliers to pull the inner nut tight in the groove of the guide ring nose.

Inner Puller Nut Is Machined With A Lip That Fits Groove In Guide Ring Nose

Inner Puller Nut Is Machined With A Lip That Fits Groove In Guide Ring Nose

Inner Puller Nut Slides Into Groove On Guide Ring

Inner Puller Nut Slides Into Groove On Guide Ring

Needle Nose Pliers Slide Puller Nut on Groove In Guide Ring

Needle Nose Pliers Slide Puller Nut on Groove In Guide Ring

Ready To Tighten Puller Bolts

Ready To Tighten Puller Bolts

I tighten the three puller bolts to pull the guide ring off the flywheel.’

Guide Ring Removed

Guide Ring Removed

Guide Ring Removed

Guide Ring Removed

Clean Bell Housing & Flywheel

Before I remove the oil pump cover, or replace the rear main seal, I clean the bell housing, and while I’m at it, the flywheel. I want the bell housing to shine and I don’t want any oil or clutch dust on the flywheel. I don’t want any of the garbage and grunge caked on the bell housing to get into the engine.

I start with kerosene and a paint brush. I brush the kerosene all over the inside of the bell housing and scrub as much of the grunge off as I can. Then I use the foamy engine cleaner to lift more of the oil and clutch dust out while removing any traces of the kerosene. Last, I use carburetor cleaner, a tooth brush and blue shop towels to get the stubborn deposits off the inside of the bell housing.

WARNING:
Wear rubber gloves while doing this as these solvents are not good for you when they get on your skin. Its a good idea to wear protective glasses as well as the carburetor cleaner can splash back at you.

Solvents I Use to Clean Bell Housing Until It Shines

Solvents I Use to Clean Bell Housing Until It Shines

Engine Ready For Cleaning In a Pan To Catch The Solvents

Engine and Flywheel Ready For Cleaning In a Pan To Catch The Solvents

Bath Time with Foaming Engine Cleaner

Bath Time with Foaming Engine Cleaner

When I’m done, the inside of the bell housing shines and it’s clean enough to eat off of.

Nice and Clean :-)

Nice and Clean 🙂

Remove Rear Main Seal

After I cleaned the bell housing until it shines, I use the Cycle Works tool to remove the rear main seal. I attach the black disk to the crankshaft nose using two flywheel bolts that I snug down by hand to center the black disk on the crankshaft.

Rear Main Seal Fits Into Bore in Engine Block Around the Crankshaft Nose

Rear Main Seal Fits Into Bore in Engine Block Around the Crankshaft Nose

Secure Cycle Works Black Disk Using (2) Flywheel Bolts and Hand Tighten

Secure Cycle Works Black Disk Using (2) Flywheel Bolts and Hand Tighten

Then I screw in the two sheet metal screws into the two small tapped holes at the outside edge of the black disk. I had to use my electric screw driver to drive them all the way in as the seal is pretty hard.

Tighten Sheet Metal Screws Into Seal Until Screw Heads Are Flush With Black Disk

Tighten Sheet Metal Screws Into Seal Until Screw Heads Are Flush With Black Disk

After the two sheet metal screws are securely screwed into the seal, I remove the two flywheel bolts. Then I screw in the large diameter puller bolt into the threaded hole in the center of the black disk until it’s snug against the face of the flywheel. I use a crescent wrench to tighten the bolt which pulls the rear main seal out of the engine block.

Removing Seal with Puller Bolt After Removing (2) Flywheel Bolts

Removing Seal with Puller Bolt After Removing (2) Flywheel Bolts

Old Seal Removed And Screwed to Black Plate

Old Seal Removed And Screwed to Black Disk

Old Seal Removed (Note Holes in Edge From Sheet Metal Screws)

Old Seal Removed (Note Holes in Edge From Sheet Metal Screws)

NOTE:
If your rear main seal doesn’t come out easily, or the sheet metal screws pull out of the seal, try heating the engine block around the seal with a heat gun. Then rotate the black disk so the two sheet metal screws cut new holes in the seal and try again.

Heating Around Rear Main Seal if Seal Won't Come Out Easily

Heating Around Rear Main Seal if Seal Won’t Come Out Easily

Revisions

2019-11-20  Edits and typos.
2019-12-20  Add Guide Ring section.
2020-01-06  Change organization for clarity.
2020-10-04  Add Cycle Works guide ring puller tool section.

10 thoughts on “11 BMW 1983 R100RS Remove Flywheel & Rear Main Seal

  1. Thanks Brook for your time and generosity in sharing these videos. They really are most helpful to amateurs like me!!. I have a 1983 R100RT taken apart ready to do a deep refurb. I have one question for you. What are the dimensions of the two sheet metal screws you use to pull the rear main seal? Are they like what we in Ireland call self tapping screws? Happy New Year.

  2. Brook, your online info is invaluable.
    I have an 88 R100RS which I purchased from PO a few years ago. Just over 100k now. My winter project was to replace PR tube seals and main seal but when removing flywheel (crank blocked) found a deformed pin and thrust washer similar to one on your blog. No luck filing to get new TW to fit. I suppose I could leave as is since existing TW and fit fit together but don’t like that idea. Not much info on replacing roll pins. I know crank will need to come out for this. I’ve started researching roll pin punches and I’m wary of damaging engine block when removing pin. Any suggestions?

  3. Dear Brook,
    I have just looked at your video and the dismantling that you have done and noticed that the clutch carrier was missing a vital washer under the carrier mounting bolts. The bolt heads had created the damage as the heads were hitting the crankshaft. It was not the impact socket.
    I hope you were able to discover that the washer was missing as you will have the same issue again upon reassembly and the bolt tensions may be incorrect as well.
    This could cause a few other issues such as carrier run out, another oil leak and a loose clutch carrier with a scary outcome.
    Regards
    Terry

    • Hi Terry,

      This is the document showing installation of the clutch and it includes a YouTube video clip summarizing the work. I used six new bolts and washers.

      21 BMW 1983 R100RS Install Clutch

      I show the six washers and they were installed on the six clutch bolts so I would be sure they were installed when I assembled the clutch.

      Best.
      Brook.

  4. I think Terry was referring to the flywheel, (missing) washer and FIVE 11mm bolts. Not the clutch with SIX smaller bolts. My 84 100S has a 5-hole washer between the flywheel bolts and flywheel. Yours looks like it had one at one time as there is a different color area on the flywheel in the shape of that washer. Your disassembly shows how the 11mm bolt heads have scored the flywheel in the absence of the mentioned washer.
    It’s part #5 on the 11_1718 diagram, part# 05: 11 22 1 335 366 WASHER (from 09/80) 0.07 1 $4.32.

  5. Actually Terry was apparently referring to the clutch.
    However I was referring to the flywheel. And there does appear that at one time your flywheel did have the mentioned washer, but when you disassembled it the washer was not there – and had not been there for at least one reassembly since the 11mm bolt heads had scored the flywheel in the absence of said washer.

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