Vintage BMW Motorcycle Owners

I'm not sure how else to install the o-ring and piston?? That's the way I did it years ago. Of course, the square o-ring needs to have some brake fluid on it to help it slide. And likely the bleed valve should be open to let the air escape.

The dust boot MUST be attached to the piston before the piston goes in. The dust boot is difficult to insert squarely. I made a tool out of 1/2in plywood to help keep things square. There is a counter-bore in the center made with a 1-1/2in hole bore bit, about 3mm deep. The counter-bore will fit over the piston. The OD is about 2-1/4in and will press the boot in.

A press is best to insert the piston and the boot, but a C-clamp will do. Use a little silicone grease on everything. Attach the boot to the piston and start the piston in until the boot is touching the caliper. Now put the tool over the piston and press the boot into the recess in the caliper. It might snap in with a loud POP! So be prepared for that.

Randy

The dust boot MUST be attached to the piston before the piston goes in. The dust boot is difficult to insert squarely. I made a tool out of 1/2in plywood to help keep things square. There is a counter-bore in the center made with a 1-1/2in hole bore bit, about 3mm deep. The counter-bore will fit over the piston. The OD is about 2-1/4in and will press the boot in.

A press is best to insert the piston and the boot, but a C-clamp will do. Use a little silicone grease on everything. Attach the boot to the piston and start the piston in until the boot is touching the caliper. Now put the tool over the piston and press the boot into the recess in the caliper. It might snap in with a loud POP! So be prepared for that.

Randy

Thanks Randy, could you send a couple of more pictures from different angles.

Sincerely,

Arturo

I stopped by Hank Arriazola's in Dilley, TX and he easily push the pistons inside the calipers.

I installed the dust covers with a dill weed spice jar lid.


The lid is the exact size to push the dust cover in place.


But you have to be very careful or you could damage it.



New brake pads.



I'm going to wait for the rain to pass to test the brake alignment. I'm sure I'm going to need to align the rotors and/or the wheel too.



I'll keep you posted.

Please do not use silicone grease unless you are planning on using DOT5 brake fluid (silicone fluid).... They do make brake assembly fluid but all it is thick brake fluid...nothing else do you ever use... I have been doing caliper rebuilds for years and all I use is just brake fluid...it works well..... and the tool you use to install the pistons is your fingers...anything else will scar the square cut seal.... it is NOT a O ring...it is a square cut seal....and when it is perfect to the bore and the piston perfect to the seal it will slide in...takes some fiddling but it works perfect and any other install trick will hurt the seal....

I don't use DOT 5 fluid as silicone will not cause rust in the bore of the caliper but often it will seep past a worn seal...DOT 4 (regular disk brake fluid works fine)....

Another trick....you need a line wrench to remove bleeder screws....sometimes they can be stuck...and they break off easily... before you break one off...take a long socket that slides over the bleeder screw and give it a couple of good wacks with a hammer....that will flex the threads in the caliper the bleeder to screw out easily...works every time...

Joel Rapose

ASE Master Mechanic

Thanks Joel, no silicone grease was used and I fingers were use to push the cylinder in place. The dust covers were carefully installed with Dill Weed.

Since the weather is getting cooler, I installed a new battery and was preparing the bike to go for a test ride, but I had an accident. I slipped and thorn the hamstring on my right leg. I´ll be out for a few weeks. The rotor test and report will need to wait a little longer.

While I was installing the new battery I managed to break a fuel tap nipple while disconnecting the fuel hose.
I ordered and replace both nipples.

A few weeks after I install the tank, open the petcocks and chock; gas start pouring out of them.
I noticed that the gas handle was stuck open and after a quick look inside the float chamber I notice that also a float was stuck open.

I tried carb cleaner to no avail. I unmounted the carbs and both are clogged.

I order a couple of Dellorto service kits and a few parts, like jets, float valves, etc.

With the carbs assembled and in it´s place, I decided to replace the choke cables.
I taped the valves and nipples together to keep the springs in place, but couldn't get enough slag to screw the plug in.





The easier way, and I tried a few different, was to bring down the air cleaner housing with the chock still attached.



And also uninstalled the choke valve housing from each carb and assemble the choke system on the bench.



After this, I install the left housing by screwing it into place.
For the right carb I had to uninstall the carb, to screw the housing in place. This because the housing is on the inside making it imposible to use a screw driver.

I adjusted the accelerator pumps following Rick Griffith´s post. http://r90sclub.dudley.nu/Newsletters/2006-09.pdf
Read Rick´s information first. Is what I followed.

I found the 3/16 id 5/16 od hose at Lowe´s and I purchased the graduated cylinders on E-Bay.





I easier to unmount the right carb to place the pipe in. The left is no problem since the pump jet screw is on the outside. You obviously need to take the screws and jets out.



No need to move the carb.

You need to plug this hole with the tape.


Like this, and don´t forget to take the tape off. All of it.






I almost left a piece there.

You will calibrate the pumps to get 6 ml on both carbs.


Mine were at 9 ml and 0 ml the left. I had to open it all the way because air bubles.


I prefer a little rich.