Hi Krew,

I hope someone has been down the path I am taking - installing an overhaul kit in the rear brake on the K100RS.

I am trying to remove the two 8mm hex bolts holding the calliper together (the ones the drive spline video says not to undo when removing the calliper from the drive tube) and I have had no success. 

I have successfully removed the calliper off the bike without trouble.  I have sprayed the ends of the screws in a good quality penetrating fluid (Inox) and left that to soak in overnight.  I have resorted to using a rattle gun (110nM) but they are not moving, except for a tiny fraction as if the seal was cracked, so I decided not to get too ambitious in case I wrenched the head off the bolt.

I believe these bolts should be tightened to 32nM but if they were, they should have come out easily at the torque setting I used.

Any suggestions?

Doug

Big problem with those bolts is that they often were put in without any lubricant and being very open to the elements they corrode and seize.
Try turning them in a bit then work away at them with penetrating oil. I have found that a mix of ATF and acetone works well, about 50/50.
I have one caliper here that is totally seized on those bolts and it will never be any good.
Sometimes using a drill to get the head off then you can work away with a better chance of getting some penetrating oil in.
Also giving a good thump with a big hammer right to the head of the bolt can loosen the crud holding it.

Thanks Rick,

I was considering using some heat on the end thread - but not sure if this will warp the casting or otherwise affect the fit of the pistons - any thoughts?

Doug

Be aware that the 'overhaul kit' you buy for the calipers does NOT include the small o-ring between the two halves near the bleed nipple/banjo bolt. Short story; about thirty-five years ago now some d*ckhead in the USA (sorry guys) bought a complete overhaul kit, got it wrong and successfully sued Brembo. WTF!!! Info from a Brembo rep when I was told no o-ring and I asked why.

You can get a LOT of heat into those calipers without causing trouble. Peel the dust seals off and go for it. The hydraulic seals can withstand very high temperatures. Also: it won't be just the threads that are seized - you will almost certainly find a lot of corrosion up around the shank of the bolt so don't neglect the heat there.

I would crack those two bolts before removing the caliper from the bike. Much better leverage.

You don't say what year.....so a little discover I made.

Generally you get a kit for 'early' or 'later' calipers. 

So for my 1984 K100RT [0022575] some years back I got 'early' kits and all was fine.

For my 83 K100RS [0011151].....these 'early' kits did not work. Very early K had different diameter [smaller] pistons.....so you need the rebuild kit for an R bike for them. Those Brembo calipers are on R bikes but reversed, so left hand front or R bike is right hand front on K bike.

Olaf: I'm guessing you're talking about the front calipers, whereas Doug is querying the rear caliper?

Dai wrote:Olaf: I'm guessing you're talking about the front calipers, whereas Doug is querying the rear caliper?

Unfortunately not. The three calipers on my RS differ from the 84 RT. The rear is same as the front ones.

Did mine on the white RS front and back  
Takes a bit of time to get these bolts to release.
 
I put mine in a vice on the bench and worked the penetrating fluid into it overnight.
Then with a big cheater bar on the socket driver + Hammer and working the bolt both directions and then allowing them to soak again. 
Whilst soaking I would rotate through all the other callipers in the same method.

A quick update.

One bolt removed, (thank you for the helpful advice); one bolt stubbornly resisting extraction.

After following Matthew’s advice I have soaked, heated, impact driven in both directions and only achieved a fair amount of impact damage on the internal hex of the remaining bolt. So, the job has been subcontracted to a local engineering firm that has undertaken work for me in the past. They have very accurate CSC milling machines and will drill out the bolt and clear the threads if they cannot shift it. The boss down there runs a competitive car in the Aust Sports sedan class and I am confident he will not butcher the job.  I should have my brake calliper back later this week.

BTW Olaf,

Mine is a 1985 RS.  When I sourced the overhaul kit from Munich Motorcycles in Perth, Western Australia, they supplied the kit based on the VIN details.  I will give them a thumbs up as they always ship within a day or two via express post if they have the parts.

Doug

I have found that even with the tyranny of distance and freight costs Motobins or Motoworks or James Sherlock in UK competes with Munich and the wait is often no longer.

Thanks Rick, good to know there are alternate sources.

Second bolt extracted - the engineering firm have bigger breaker bar than me (or they are just younger, fitter and stronger!).

As Dai said - they were stuck all the way up to the head of the bolt.  The hex profile on the second more stubborn bolt has suffered from all the impact wrenching, so I plan to replace it - maybe both and keep the better one as a spare. A couple of pics showing the bolts attached.


The overhaul kit is also pictured - note the two small o-rings.  But what are the two large ones for? 


Doug

Doug: I'm assuming that by 'the two big ones' you mean the caliper seals in the middle 'column' of your pic. The ones on the right are the dust covers. Check the two halves of the caliper; if you can't see a groove of the same size as the caliper seals, then the old ones are still in there. Look very carefully; when you find them, you should be able to lever them out with a thin screwdriver. I always put the new ones in with a good layering of silicon grease as this also helps when inserting the piston. When you insert the piston, push it all the way down as far as it will go as this helps with bleeding the brakes because it reduces the air space in the calipers to an absolute minimum. The pistons should still sit up enough to allow you to push the dust covers on, similar to how the old piston is sitting in the pic.

The fact that you ask about the caliper seals has me slightly worried. Have you done this job before? If not, please find someone who has done it to stand over you as you overhaul the caliper. Your life could depend on you getting it right.

Dai,
Appreciate your concern for my welfare.
Yep - This is my first attempt at overhauling any disc brake - my car is a 1953 Armstrong Siddeley which has drum brakes all round and I started doing my own maintenance after I retired from full time work a few years ago…..which is why I appreciate all the knowledgeable advice and guidance generously provided on this forum.

I hadn’t popped the pistons out yet - so I found the old seals once I had done so. Then it became obvious what those big things were! I shouldn’t have jumped on the forum so quickly. To reassure myself that I am not doing anything badly, here is a description of what I have done:

I’ve used a thin brass wire brush in my drill to clean up all the internal threads, cleaned everything (callipers, pistons, bolts, spring and retaining pins)with parts cleaner, flushed and rinsed in brake cleaner and blown everything dry with compressed air. 

I used the silicone oil in the kit to coat the seals and lubricate the piston - taking care to make sure none of the oil found its way onto the outside surfaces. Installed the dust covers, put in the small o-rings (also with a light smear of silicone oil) put nickel based anti-seize on the bolts  and reassembled the two halves of the calliper. Made sure any surplus oil or anti-seize was removed with a rag soaked in brake cleaner.

Then reattached the brake line, fastened the calliper to the drive tube (again with nickel based anti-seize) replaced the bleed nipple and tightened everything up to the spec on page 34-05.0 of my Repair Manual.

I haven’t received the brake grease I bought from Wurth yet, so when it arrives I will apply to the brake pads where they rest on the callipers as well as the spring and pins before reassembling.  I believe I am then ready to bleed the brakes, but I will first flush them through and ensure I have all new brake fluid in the system. My running in process will only use the rear brake lightly for about 250km then I will find a quiet back road and do 10 hard stops from 100kmh.  After that I will use the rear brake normally.

If there is anything I haven’t done or will do I would welcome the advice.  

With a bit of luck, I should soon have a serviceable rear brake again!

Doug

Sounds all good to me!

Old school and usually the best way too.

Just a short post to thank everyone for their input and let you know the rear brake is back in operation with a firm pedal.  Haven't been out for a test ride yet - problem traced to fuel injectors - and that is another post in the story of getting my K operational.

Doug