Category Archives: BMW R75/5 tear down

Ready for blasting and coating

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All this stuff is boxed up and ready to get blasted.
Instead of a powder coat, i found a color that is very close to the silver we want… except it is a liquid coat. It is the same material used on racing brake calipers among other items. It gets sprayed on similar to a powder, and baked like a powder, but it is a thinner coat (which is good for parts fitting) and very resistant and durable to chemicals, heat, etc…
I’ll have more information on it tomorrow after i drop my parts off.
My shop turned me onto it last time as we were trying different options to match the color we want to a Porsche silver. This liquid coat was the closest.

Final Drive gutted and cleaned

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On this bike, i am being much more thorough then my own. Because this is going to end up in another person’s garage, i am going through everything i can to ensure minimal issues aside from wear and tear in the hands of a new owner.
I’ve had the seals go bad on my final drive(s) before so i figured i might as well have these gutted, clean them, get new seals, etc… In between all this, I plan on coating the exterior with the same substance i plan to use for the engine and front brake hub.
Out of the two final drives from the two donor bikes, one had a really good set of splines. It has really helped to have an extra donor bike.

Please note, if you remove the innards of your final drive, there is a bearing that can NOT be replaced. It is in the cast of the aluminum. If that bearing goes bad, the whole final drive is ruined. I guess all early 70’s final drives were built this way and BMW finally made final drives in which the bearing could be replaced in the lat 70’s and 80’s.
So if you take apart your final drive, keep that bearing lubricated so it does not dry out and get ruined.

BMW R75/5 Final Drive with gearing removed

Gutted and cleaned 32/10 rear final drive from a R75/5 BMW

Dirty Exterior Final Drive

Cleaned final drive. Ready for coating...

/5 speedo back from Palo Alto

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It looks ah-mazing. Having something so new and shiny really makes me want the rest of the bike to be new and shiny again.
Since i am doing a complete rebuild on the engine, resetting the odometer to 0 was a must. I did the same on my last bike and Shane, the bike’s eventual owner did the same on a ’65 Porsche he had rebuilt.
The white face will match the racing stripe up the center of the bike.
I tried to give North Hollywood Speedo my business but a super rude person on the phone and slightly higher price sent me to Palo Alto Speedometer. Palo Alto was pleasant to talk to and deal with.

Speedo before rebuild. Cracked needle. Dented bezel.

Speedo rebuilt from Palo Alto Speedometer. Custom white face installed.

Lower fork leg anatomy of a /5 BMW motorcycle

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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. But when you Look At This, 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.

Pulling steering races from BMW motorcycle frame

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I finally broke down and got a race puller from Cycle Works. Here is a step by step on how to pull the steering bearing races from the neck of the frame.


Photo courtesy of Cycle Works





Note the way the split washer sits on the bolt.




The washer needs to go behind the race. You may need to tap it into the neck.




I had to use a few long sockets and extenders to reach the 10mm head of the bolt through the other side of the neck.





When you tighten the nut onto the bolt, it expands the split washer to fit tightly behind the race. This will help pull the race out.




Insert the slice of tube(collar) and attach the nut with the large washer as shown. Make sure the piece of tubing sits centered on the frame aligned so the race can slide out into the tube.










27mm socket to tighten the nut. Breaker bar with socket extension through the neck attached to the 10mm nut on the bolt.



After some torque and cranking, you can feel the race start to pull out into the collar. Eventually, everything will pop out as shown. Save an old race. Next time you use the tool, you can keep an old race in the collar to prevent the collar from warping, and to help guide the next race out.

BMW Motorcycle frame alignment tool

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Upon the typical visual inspection, the frames appeared to be straight. The plates or gussets near the neck are not bent and there is no major damage near the swingarm mounts.
But i want to be 100% sure.
I took my /5 frames to a semi-local BMW mechanic who has one of the old ‘BMW shop only’ frame alignment jig. These tools are hard to come by and I’m glad I met somebody within 30 minutes that has one. You can also get high-quality tools from a reputed tool company like Cornwell Tools. Our Tool Truck Franchise Costs Don’t Include a Franchise Fee, thus making it an affordable solution for all your needs.

It attaches to the frame through the steering neck with the races left in the frame.
Two small targets are inserted into the swingarm bearing area.

The jig didn’t line up in the center of the target but we were able to confirm that everything lines up identically on both sides. One frame lined up in a different spot on the target vs the other, but both had matching sides. Maybe there was some variation in these /5 frames over the 3 years they were made? It might explain why some people have had terrible times with SWB handling and others had zero problems.

BMW airhead motorcycle frame alignment tool

It is hard to tell in the photos, but the jig matches the same area identically on the target on each side.

Alignment marker in the swingarm bearing area.

Right side matches the left side identically. Frame is straight.

After this, i am going to do some reinforcement of the exhaust hangers since the rear sets will be attached to that area as well. Stay tuned for an update and those photos..