Lower fork leg anatomy of a /5 BMW motorcycle

A photo diary of the internal components of a /5 BMW motorcycle fork leg.
I plan on rebuilding these forks entirely.  Good thing too.  The rubber is completely rotted in some spots and it has over 10 years of fork oil sitting in these legs. NASTY stuff.

I snapped these photos partly for the blog, but also for my own memory when it comes time to replace many of these parts and reassemble everything.  Please excuse the beat up linoleum floors in my garage.

Feel free to comment or ask any questions. I didn’t plan on this being a ‘How To’ post but more of a photo of the pieces and parts involved in the forks. But the post ends up being a bit of both…

Please note, i removed the entire fork assembly from the frame.  The fork rebuild can be done while still attached to the bike. When i go through the reassembly, and mount them to the triple tree, i will have to perform a strict alignment procedure to make sure the forks are installed properly.  A misaligned set of forks can cause some harmful results to the rider.  I will be sure to post my realignment procedure when the time comes.  In the meantime, for reassembly, please refer to Duane Ausherman’s site on fork alignment:
http://w6rec.com/duane/bmw/forktool/index.htm

Also, please note that i drained all the fork oil prior to starting this procedure.

I removed the upper chrome fork cap with the BMW tool

BMW fork cap pin wrench.

I then removed the upper fork bolt that secures the fork leg to the top triple tree and maintains pressure on the internal fork spring.  I believe it is a 36mm nut and it can often be secured very tightly. I recommend getting a 38mm socket and a breaker bar for the removal process.  The BMW fork wrench is often too small and you can not get the leverage needed to get that nut loose. Before i had a 36mm socket, i remember removing these nuts extremely difficult.
I snapped the following photo so i can remember that the nut had a washer, and the size of the spring spacer.  Some models do not have a washer between the nut and the triple tree. And some spring manufactures like Progressive supply a PVC piece of pipe to cut down to size for spring tension. A longer size will equal more tension. I will probably stick with the spacer that the bike has on it.  It’s a nice aluminum spacer vs PVC.

Upper fork cap removed and upper fork bolt removed.

 

The pinch nut for the lower triple tree needs to be removed and then the fork tubes should slide out from the triple tree.

Lower triple tree pinch nut and cable hook on right side fork leg.

 

 

The springs were taken out and the fork legs removed.

Fork Legs removed.

 

 

You need to grind a flat edge on either side of a 13mm socket.  Then install a hex (Allen) wrench in the hole of the socket.  Hold the Allen wrench in place and loosen the nut.  This will separate the chrome fork tube from the lower fork leg (lower fork slider).

Special filed down socket in which an hex tool can fit through and a wrench can keep the socket secure. Also in the photo is the 30mm socket for removing the bottom cap from lower fork leg.

 

 

I really need to invest in a good circlip tool.  I have bought a few and they never seem to have the correct tension for the precision needed in removing and installing circlips.
The circlip needs to be removed from the bottom of the chrome fork tube.(FigureA)
Then you need to unscrew the lower threaded ring from the base of the fork tube. I used needle nose pliers to fit into the small holes of the threaded ring. (Figure B – though the /5 ring looks different)

Image taken from Clymer Manual. BUY ONE!

 

Here is a shot of the first stage of my fork disassembled.

First photo of fork anatomy.

 

 

I already unscrewed  the threaded plug from bottom of the dampener rod.
This photo shows how to remove the upper dampener piston.

Internal fork actuator disassembly.

 

Photo of entire fork components… in order of their removal.

Entire fork disassembly.

 

Close up of the lower dampener rod’s threaded plug, spring and ball.

Close up of lower nut, spring and ball.

 

Close up photo of the orientation and order of the upper dampener rod and the upper piston for the dampener rod.

Close up of upper fork piston.

BMW Airhead Clutch and Flywheel Removal on the Cheap

It’s been about 5 years since i have pulled a flywheel and a clutch from an airhead engine. I do remember the process being slightly ‘dangerous’ in that if you don’t remove the clutch properly, the force of it could cause harm to yourself or your motorcycle.  I don’t have the BMW ‘special’ tools at my disposal to do so safely… so i figured i would make my own. Total cost – $10 from my local Ace Hardware store (which happens to have the best spare bolt, nut, screw selection i’ve ever seen).
No need for the BMW Special tools.

Clutch Removal

You will need to purchase three M8 x 1.00 thread (fine thread) bolts about 2 inches long.
i also purchased a small piece of aluminum tubing that fits around the bolt:

M8 x 1.00 bolts and aluminum tubing. Bolts cost $1.50 each(damn pricey metric fine thread bolts)and tube was $2.20

 

The first step is to remove every other bolt on the clutch disk that secures it to the flywheel:

I cut the aluminum tubing into three sections about 3/4 inch.
Then screwed in the 2 inch long bolts with the tubing on it into those every other holes:

Bolts with spacers on them

The reason for the bolts with the spacers is to safely alleviate the pressure into a ‘second’ stage.  When you remove the three remaining ‘factory’ bolts, the disk’s pressure releases itself outward, safely, onto the spacers:

Clutch pressure now lessened and on the bolts with the spacers.

Now it is simply a matter of removing the remaining 3 bolts, evenly, until the clutch disk is released.

If your bike has these spacers, Keep them! Some clutch disks don't.

Clutch bits, friction plate, etc...


Flywheel Removal:
To remove the flywheel, you have to prevent the engine from turning while removing the flywheel bolts that secure it to the crank shaft.
Also, without securing the flywheel, you can also run a risk of knocking the inner thrust washer (around the camshaft) off the pegs within the inside of the engine block. SERIOUS damage could occur within your engine case if that happens.

BMW recommends a ‘special tool’ but it is merely a device that locks the flywheel in place.
I made my own from a piece of steel for $2.00.

12" piece of steel.

After some quick cutting and drilling, I have my very own version of the ‘special tool’.
Use the original flywheel bolts, and finger tighten them as much as you can and you are now free to use a nice breaker bar, a 17mm socket(i think) and crank out those flywheel bolts.
Some suggest using a center punch and making a small score on the crank shaft and another on the flywheel so you can put the flywheel back in the exact same position and your TopDeadCenter mark is still accurate.  Using a permanent marker might do the trick for a short term solution.

Piece of steel, cut and drilled out to prevent the flywheel from moving.

That’s it!  Now that the flywheel is removed, time to send it off to get lightened!
Another note while the flywheel is out… some people put white paint on the timing marks so you can see them better when timing. Just a tip….

Oh… and remember to THROW AWAY the 5  flywheel bolts. They are torque specific bolts and once they are torqued to spec, the can’t be used again. If so, they may wiggle back out and cause some SERIOUS damage.

For more info on clutches and flywheels, look here:
http://bmwmotorcycletech.info/flywheelremovalwarning.htm
http://bmwmotorcycletech.info/clutch.htm
Measure your clutch parts – http://w6rec.com/duane/bmw/clutch/index.htm

Northwoods airheads sells a $4 crankshaft blocking bolt to prevent the crankshaft from moving forward when removing the clutch / flywheel.
it is located here. http://www.northwoodsairheads.com/Tools.html