Category Archives: BMW cafe Motorcycle

BMW Cafe Motorcycle R75 build

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...

Rear Set mount preparation

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Before i get the frame blasted and powder coated, i did a test fit with the rear sets. On my last bike, i mounted the rear sets to the plate that the mufflers hang from behind the swingarm bearings. I had to create angled shims to get the rear sets to mount perpendicular to the frame. If they didn’t have a shim, the rear set foot pegs would point slightly forward.
The same holds true with the Disco Volante rear sets i am using on this bike. Lesson learned from the last bike… this time BEFORE powder coat, i enlisted a welding buddy to help me create a solid mounting area for the rear sets.
In addition to the rear set mounts, i am also going to fill the holes for the passenger foot pegs and the saddle bag mounts.

BMW R75 swingarm pivot and muffler hanger plate





Rear set mounting hole but notice the gaps.





Small gap on the right side foot peg





In addition to making a better mount for the rear sets, i need to fix the common crack that occurs on the mounting tab. It is often caused by road elements, or the battery drain tube, or rear passenger stress, etc...



AFTER PHOTOS:

New Rear set mount and passenger footpeg and saddle bag holes filled.





Nice and perfect mate between the foot peg and frame.





perpendicular foot peg mount.





another perpendicular shot





Shot of the inner side. My buddy welded the crack and then went a bit overboard with the thickness of the plate he welded to reinforce that area. But I figured it couldn't hurt to have too much metal back there. Especially if that plate will need to handle the weight of somebody's legs/body.





I did a bit of sanding and polishing to smooth the area in preparation for powder coat. It is going to look nice and clean back there instead a stock frame with the passenger footpeg holes and such.

Fix leaking fork brace studs

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On the /5 BMWs, there is a chrome horseshoe that acts as both a fender mount and a lower fork brace. The studs that connect the fork brace to the fork sliders are part of the slider and can potentially leak. One of mine has slowly leaked on my /5 for years and i haven’t around to fixing it yet.
For this bike rebuild, i noticed that out of the 2 sets of fork sliders (4 sliders from 2 bikes), one leg was leaking terribly due to all the dried oil residue down the front of the fork slider.As i was disassembling the second set of forks, one of those studs came out instead of the nut coming off… so i got to thinking (and got some advice from some BMW pros), i should re-seal all the studs to be safe.

The tools needed for the job are:
The original 13mm nuts.
2 13mm wrenches
a long 13mm socket would help too
vice
channel locks or pliers
a heat gun
and some RED Locktite

Here is the fork leg with one of the studs removed:

Fork slider with one stud removed, another about to be removed.

 

 

Double nut to remove the old stud. Tighten these two nuts tightly together:

Double nut to remove the old stud. Tighten these two nuts tightly together.

 

Loosen the lower nut and it will remove the entire stud.

 

Inspect the threads of the studs. Out of the 2 sets of fork sliders, i had about 6 good studs.  2 were too rusty or bent to reuse. After inspection, i did a quick cleaning on the wire wheel to clean up the threads.

4 removed studs and red locktite.

 

 

I then replaced the nuts on the longer threaded end of the studs. I pinched the middle part of the stud that is not threaded in a vice and tightened the nut as much as i could.

Then i wrapped part of the fork slider with a rag and clamped it in a vice.
I used a heat gun to heat the fork slider to get the metal to expand. I spent a good amount of time heating the legs to a very hot temperature.

I then added red locktite to the threads of the stud and inserted the stud into fork slider by using the nut and a 13mm socket to tighten it into the slider. I went as far as i could, as fast as i could before the slider cooled down.
*** But please look into the fork slider (flashlight helps) and make sure you don’t drive the stud too far into the leg where it will hit the fork tube. If the stud goes too far, it will prevent the slider from operating properly on the fork tube, or severely damage the fork tube.
When the fork slider cools down, and with the use of Locktite, it should create a nice tight seal around the stud and not leak again.

Tightened studs back into fork slider.I backed off the nuts from the stud and Yeah, i used a bit too much locktite.

/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.

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..