00 BMW 1973 R75/5 General Tear Down

This write-up documents the tear down to the frame of my wife’s  1973 BMW R75/5.  You can find other material on this project in the list on the right side of this page. As appropriate, I reference other pages I’ve written about this project. I decided to number the sections I write with the leading two-digits of BMW’s part numbers. This identify major sub-systems of the bike.  Hucky’s uses the same method to categorize parts for the R75/5 as shown here.

I like to take a lot of pictures as I take things apart.  That way, many months later when I’m putting this bike back together, there’s a decent chance I’ll have a picture that shows me exactly how the whatzit is aligned with the doohicky as I’m screwing in the framis assembly.

Where to Start?  At the Beginning, Of Course.

I did a visual inspection and took several photo’s of the bike before I started taking things apart. This helped me identify obvious things that are going to need to be replaced or repaired. Then I sat down and wrote up a high level work plan to organize my thinking about how to proceed. You can see the pictures and my high level plan in 01 BMW R75/5 Planning the Build.

I started at the front and generally moved to the back as I took the bike apart. Here’s the bike in the shop I built last year before the parts started coming off.

In the workshop

Fully Assembled “Before” Picture

The other thing I do is to bag the parts in freezer zip-lock bags and label them with a Sharpie as I go. Then, in the evening when I have some time, I open a bag and clean and refinish the parts and put them back in the bag. I have two stacks of bags, one to clean and refinish and the other stack is parts ready to install. Parts bagging helps keep from loosing parts and simplifies putting things back together.

Remove the Fairing and Front Fender

I removed the Windjammer II faring and the front fender first. I’m going to restore the Windjammer II using parts available from Craig Vetter himself.  I already ordered what I need and got a note from his wife, Carol, letting me know they had shipped.  That was very cool for an old fart like me who remembers when his fairings were the touring rider upgrade of choice.

The headlight shell plastic cover was torn many years ago and still has the electrical tape bandage I applied to it to keep the water out of the headlight shell. When I pulled the cover off, the insides of the headlight shell showed no corrosion.  Those were the days when electrical tape was stout stuff.

Faring & fender off

Front Fender and Fairing Removed

Remove the Gas Tank, Seat, Carburetors and Mufflers

Next, I removed the gas tank, seat, carburetors and the exhaust system. Here’s the seat, tank, and disassembled exhaust system.

Parts

Seat, Tank, Front Fender and Exhaust System Removed

The exhaust system has some corrosion as shown below. I’m going to work on polishing the headers, but after inspecting the cross-over pipe, I’m planning on getting a new one due to the amount of pitting and missing chrome.  New mufflers are also part of the parts list as these have been mismatched since we got the bike in 1978.

Header corrosion
Some Corrosion on Header Pipe

Header corrosion

This is the bike after removing the exhaust system and carburetors. You can read about how I rebuilt and refinished the carburetors in 13 BMW R75/5 Bing Carburetor Rebuild.

Carb removed

Exhaust and Carburetors Removed

Remove the Engine Top End

I then moved on to disassemble the top-end of the engine removing the exhaust system, valve covers, valve train, cylinder heads and then the cylinders and gaskets. After that, I removed the battery and air box.  You can see this procedure from the top-end tear down of my 1975 R75/6 in the blog post “The Grey Ghost Restoration-Part 3 Engine“, so I won’t repeat that procedure here as it’s the same for both the /5 and /6 models.

Here’s what it looks like after getting the valve covers, heads, cylinders and gaskets removed. I used a paint stir stick to keep the connecting rods from bumping on the engine block. After I removed the pistons, I put some wire through the connecting rod end and wrapped it around the cylinder head studs to keep the rods elevated.  I stuffed some red shop rags into the opening to keep anything from getting inside the engine.

Cylinder off

Top End Removed

Here’s the box of parts going over to Roadies for bead blasting. I shipped the heads to Randy Long at Long’s Mechanical Services to have them rebuilt. He did the heads on my R75/6 and he’s  my go-to-guy for head work.

Cylinder & valve covers for bead blasting

Parts Ready to For Bead Blasting

Then, I removed the air box covers, air filter and the battery. Here’s the bike at this point.

Pistons Removed

Top End, Battery and Air Box Removed

Then I removed the battery brackets from the frame.

Battery Box Rust

Right Side Battery Bracket Before Powder Coating

Battery Box Rust

Left Side Battery Bracket

Remove the Front Wheel and Brakes

Next, I pulled the front wheel and front brake assembly off. I took the brake shoes out to inspect them and also removed both brake arms. This bike has double leading shoe front brakes for more stopping power so there are two arms to activate the brake shoes.

Front Brake Cover
Front Brake Cover Showing Both Brake Arms

Here is the brake arm removed and the inside ferrel that holds the brake cable.

Front Brake Cover Levers
Front Brake Cover with Brake Arm Detail

Here’s the details of the brake shoes. Note one return spring is longer than the other. The  pivot pin is on a shaft that the brake arm connects to. It is held on with a c-clip. I think this will help me get the shoes and springs back together in the correct orientation.

Front Brake Cam & Pivot Detail
Front Brake Shoes, Springs and Pivot Arm Detailf

Remove the Wiring Harness and Electrics

The next step is to remove the wiring harness and electrics. Since I’m going to powder coat the frame everything has to come off.  I wrote a separate page,  61 BMW R75/5 Removing the Wire Harness & Electrics, covering the disassembly of the wiring and electrics.

Remove the Handlebars, Controls and Fork Tubes

With the wiring harness disconnected from everything but the the headlight shell, I removed the handlebars and right and left control assemblies and fork tubes as I described in page  31 BMW R75/5 Fork Rebuild.  Below is a short summary of that page.

First, I disconnected the throttle, choke and front brake cables from the controls. Next, I removed the controls and disassembled them as shown below.

Right Control Disassembled

Right Side Control Disassembled

Left Control Disassembled

Left Side Control Disassembled

Then, I removed the handlebars and pullbacks that were installed on this bike.

Handle Bar Bracket & Pull Backs

Handlebar Bracket with Pull Backs

Then, I removed the steering friction damper rod and friction plates from the bottom steering stem clamp by unscrewing the rod using the black knob on top.  Then I removed the bolt and lock nut holding the friction plates to the bottom side of the triple clamp on the steering stem.

Steering Damper Disassembled

Steering Damper Friction Assembly

Here’s a picture of the steering head assembly with fork tubes still attached which is the next target for disassembly.

Handlebars Removed

Steering Head After Handlebars and Controls Removed

Remove the Fork Tubes

The details about removing the fork tubes is covered on the  31 BMW R75/5 Fork Rebuild page. At this point, the steering stem is still connected to the steering head with the slotted nut. I removed the nut with the hook spanner  tool in the bike’s tool kit. The chrome dust cap pulls off and I’ll replace it as the chrome has come off in several places.

Fork tubes removed

Steering Head After Forks Removed

Using a rubber mallet, I knocked the steering stem out of the steering head. The upper stem bearing is a shrink fit onto the stem and will slide off the stem, but it takes a couple of firm blows to slide it up.  Keep you hand under the steering stem to catch it so it doesn’t slam into the floor.

Steering Stem

Steering Stem Showing Top Bearing

Remove the Rear Wheel, Fender and Sub-Frame

At this point, I put some bracing under the front of the oil pan and some jack stands under rear of the frame where the mufflers mount on the bike so it doesn’t pitch forward when I remove the rear wheel.

Supporting the bike before rear end and swing arm removal

Bike Support After Removing Rear Wheel

Then I removed the rear fender, shocks and the seat sub-frame.  The seat lock is secured to the sub-frame. Remove the bolts on the backing plate to expose the internal locking assembly.

Seat lock outer cover removed

Seat Lock Outer Cover Removed

To remove the lock assembly from the frame, unscrew the single screw from the back of the locking ring around the lock mechanism.

Removing screw on seat lock retaining ring

Removing Screw From Seat Lock

Seat lock key & retaining ring

Seat Lock Retaining Ring and Lock

Here is a picture of the internal mechanism of the seat latch button assembly. I took this in case the innards come loose at some point so  I can get the spring aligned correctly.

Seat lock internals

Seat Latch Button Assembly

Remove the Swing Arm

I find removing the swing arm from the transmission output shaft is easier if I re-install the rear wheel and also put the transmission in 1st gear.

Rear wheel for keeping shaft from turning

Reinstall Rear Wheel

I removed the steel bands on the rubber boot between the transmission output shaft and the swing arm. Sliding the boot off the transmission exposes the four 10 mm, 12 sided bolts that connect the drive shaft coupling to the transmission output coupling.

Pulling Rubber Boot Exposing Universal Joint

Pulling Back Rubber Boot Exposing the Universal Joint

These are on very tight.  I rotated the rear wheel to align one bolt so it’s on the right side at the 3:00 position. This way, I can get the 12 sided, 10 mm closed end wrench in the tool kit on the nut since the output shaft coupling rotates to provide more clearance behind the bolt head.

Removing drive shaft bolts

Bolt at 3:00 with 12-sided Closed End Wrench

Then, while sitting on the rear wheel, I use a hard rubber mallet and hit the wrench on the end to get the bolt to back off. Make sure the box end is flat on the end of the bolt or you can round it off and then you have a real job on your hands. I go around loosening all the nuts and then remove them. This picture is from the Grey Ghost 1976 R75/6 rebuild (note the garage setting, cast rims and my son doing the work) but there is no difference between the /5 and /6.

Sitting on Tire to Keep Drive Shaft from Turning

Sitting on Tire to Keep Drive Shaft from Turning

When the bolts are removed, THROW THEM AWAY. These are stretch bolts and should not be reused.  If I throw them away I won’t mistakenly reuse them.

Remove the Rear Drive

Now, with the swing arm and rear drive off the frame, remove the rear drive by removing the four nuts that attach the swing arm to the rear drive unit. There is a gasket between the rear drive and the swing arm so you may need to bang on the rear drive with a rubber mallet to get the rear drive to come loose

Rear Drive

Rear Drive Removed from Swing Arm

Here’s what the bike looks like now.

Subframe, wheel and fender removed

Ready To Remove Swing Arm From Frame

Now, remove the swing arm plastic covers at the pivot point to expose the nuts. Use a turned down 27 mm socket to loosen the nuts. You can make one if you have a lath, or you can get one from Cycle Works, as I did.

Cut Down 27mm Socket

Turned Down 27mm Socket

When you get the nut removed, use an allen wrench to unscrew the swing arm bearing out.

Pulling the Swing Arm Bearing

Unsrewing the Swing Arm Bearing

At this point, the swing arm is free from the frame. The drive shaft is still inside the swing arm. I did not remove the drive shaft as I have no need to disassemble the drive shaft. From what I’ve read, the rear drive coupling has a 150 ft-lb nut and shrink fit to contend with if you want to pull the shaft out of the swing arm.  I can repaint the swing arm as is so no need to disturb the drive shaft assembly and risk damaging it.

Swing arm disassembled

Swing Arm Assembly: 27mm nut, Threaded Bearing and Swing Arm

Remove the Transmission

Below is a diagram of the clutch throw-out mechanism from Max BMW Parts Fiche. I’ll refer to the parts by number. The clutch throw-out arm (14) is mounted to the back of the transmission. On the /5, there is a cotter pin (11) holding a pin (13) that goes through the arm and the cast bushings on the back of the transmission. Remove the cotter pin and then the pin shaft holding the throw-out arm. Then you can pull out the throw-out arm from between the bushings. The rubber cup (7) and the spring (15) will come with the shaft.

Clutch Throw-out Arm and Bearing Detail

Clutch Throw-out Arm and Bearing Detail (Source: MAX BMW Parts Fiche)

With the throw out arm removed, there’s room to slide the transmission back to the strut across the rear of the frame to remove the transmission input shaft from the engine.

Transmission rear crud

Rear of Transmission after Removing Throw out Arm

There are three allen head bolts and one nut holding the transmission to the engine, each at the four corners of the transmission housing.  Remove these and carefully slide the transmission to the rear so the transmission input shaft comes out of the the engine output splines.  The transmission isn’t very heavy, about 20 lbs or so, but you don’t want to mangle the splines on engine output and the transmission input shaft. Below, you can see the clutch throw-out rod (1) in the center of the transmission input shaft.

.Transmission input shaft splines - rusty but ok

Transmission Input Shaft Splines – Rusty but ok

Clutch splines - rusty but ok

Engine Side Splines in Clutch Housing – Rusty but OK

In the picture below, you can see the clutch throw out bearing (5) with the throw-out shaft (1) behind it near the center of the transmission.

Transmission crud

Back of Transmission with Throw-out Bearing to the Right of the Kick Starter

You can push the throw-out shaft (1) from the front of the transmission to the back. The throw out bearings (4) will come out with the throw-out shaft.  Here’s a picture of the throw-out bearing and the throw-out arm.

Clutch throw out shaft & baring

Clutch Throw-out Bearing and Throw-out Arm

And pictures of the ends of the clutch throw-out shaft. There doesn’t appear to be any abnormal wear so that’s a good thing.

Clutch throw-out rod

Clutch Throw-out Rod End

.Clutch throw-our rod

Clutch Throw-out Rod, Other End

Remove the Engine From the Frame

Here’s what the bike looks like at this point.  I put  some scrap 2×4 and 4×4 under the front and the back of the oil pan. The top of the stacks are about 1 inch below the oil pan.

Ready for engine removal

Bracing Under Oil Pan

There are two threaded rods under the engine that go through the frame securing the engine to it. I removed the nuts on the left side when I removed the front foot peg and the side stand earlier.

Push rod tube leaks

Front Engine Mount Holds Side Stand Assembly

40 yr old foot peg rubber

Rear Engine Mount Holds Front Foot Peg To Frame

The engine weighs about 70 lbs so its easy with one hand to pull up on the front of the engine to take the strain off the front engine mount and then with a rubber mallet and screw driver, I knocked the front pin out and let the front of the engine down on the wood. The same procedure got the rear engine mount out of the frame. Now, the engine is resting on the wood blocks.

The frame is now free of the engine, so I slid the frame forward until the engine was at the rear of the frame against the rear cross brace. My son removed the engine while I kept a hand on the frame. On the left side of the engine, he could get a good hold on the bottom of the timing cover and the other hand under the rear of the bell housing.  It was quite easy to lift it up  and out of the frame. Be careful as you lift the engine to not hurt your back. Use your legs and straighten them to lift the engine and be sure you can back up a couple of steps so you can put it down without tripping over anything behind you.

I put some blocks of wood in the center of my Park-n-Move dolly and put the engine on the wood and then strapped the front and back to the dolly so I wouldn’t accidentally damage the engine.  The wheels lock on the dolly so this is a convenient way to move it around the workshop.

Another use for Park-n-Move Dolly as Engine Stand

Another Use for my Park-n-Move Dolly – An Engine Stand

And, here’s the end result, a naked frame ready to go out for powder coating.

Bare Frame

Frame Striped Bare – On to the Powder Coater

One comment I got was to check for possible fractures where the gussets connect the rear foot peg and muffler mounts to the frame.  I didn’t find any.

Looking for Stress Factures to Gusset

Looking for Stress Factures to Gusset

Looking for Stress Fractures on Gusset

Looking for Stress Fractures on Gusset

This is the first time I’ve stripped a motorcycle down to the frame. Cross one more off my MC building bucket list 🙂

18 thoughts on “00 BMW 1973 R75/5 General Tear Down

  1. Pingback: 1973 BMW R75/5: Tear Down to the Frame | Motorcycles & Other Musings

  2. Pingback: 1973 BMW R75/5: Replace Swing Arm Bearings & Powder Coat | Motorcycles & Other Musings

  3. Brook:

    You’re posts describing the rebuild of the R75/5 have been invaluable to me in my tear down of my project.
    Thanks for taking time to meticulously document the process.

    Regards / Dennis

  4. Brook,
    I am trying to remove the tachometer cable from the timing chain cover, but it is stuck and will not pull out. Got any ideas here? Thanks.
    Dan

    • Hi Dan,

      If I remember, there is a bolt that holds a sleeve bushing on the end of the cable in the hole it mounts inside of. That sleeve has a slot on one side the bolt slides through to keep the sleeve from rotating.

      I think I used a bit of Kroil pentrating lubricant (you could try any of the other rusty nut penetrating oils) to help get the bushing to slide out of the sleeve. It took some pursuading to get the sleeve to move in the hole as it is a tight fit and any crud will make it hard to slide the bushing out of the hole.

      I hope this helps.

      Best.
      Brook.

  5. Hi. I am refurbishing a BMW R80 1984. I see that you didn’t disassemble the drive shaft. I assume you had it powder coated? I am a bit nervous about exposing the UV joint to the 350 degree curing temperature.

  6. I wish I’d found your website when I first began the rebuild on my ’76 R75/6. Luckily I’m only now starting the reassembly so I’ll be able to come here for some invaluable pointers.

  7. Brook,

    I’m stoked to have found your blog. I recently purchased a ’71 /5 SWB, and have started the teardown in earnest. I’m sure your blog will serve as an invaluable resource. The Airhead world owes you a debt of gratitude. Cheers!

    • Matt,

      I’m pleased to here that you are going to bring another airhead back on the road. Awesome!!!

      Best.
      Brook Reams.

    • Hi Scott,

      You’re quite welcome. I’m pleased the material is helpful to you. I never met a beer I didn’t like 🙂

      Best.
      Brook Reams.

  8. Him I’m having trouble getting the front engine mount through bolt out ,it’s solid . Any Ideas . It’s an r65ls . Thanks karl

    • Hi Karl,

      Well, a couple things come to mind.
      0. Check to be sure NOTHING like the frame, exhaust, etc. is preventing the bolt from coming out. (Yes, this is kind of obvious, but on occasion the obvious gets in my way 🙂 )
      1. If you can, try to lift up on the bottom of the oil pan with a floor jack pushing up on a piece of plywood or 2 x 10 scrap on the bottom of the oil pan to take some of the engine weight off the front engine bolt so it can slide.
      2. Use some rusty nut lubricant and spray some along the sides of the engine bolt on both ends to loosen any rust that may be impeding the bolt from moving.
      3. After #1 and #2, use a drift (a socket or even a smaller diameter bolt will work) a bit less than the diameter of the bolt and a larger hammer and pound on the drift to see if you can drive the bolt to one side.

      The MAX BMW parts fiche doesn’t show anything except the threaded rod, aka “bolt”, and the nuts and washers on either end, so it is meant to slide through the engine case.

      I hope this helps.

      Best.
      Brook.

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