Front brake master cylinder can't get brake lever off

[ajd]

I was going to change the master cylinder piston and seals on my 1100GS because there was a weep. Went to remove the brake lever and imagine my surprise when the pivot screw wasn't there. At least, the head wasn't. It all makes sense now - it was weeping a while ago, I took it to someone to replace the seals, the weeping never got better but wasn't bad so I thought 'it was meant to do that'. I reckon the bloke either snapped the screw or found it was snapped when he got there so didn't change the seals and took me moolah anyway. Fascist.

If I've uploaded the picture right you can see where the screw isn't (between the throttle cable and the brake light switch). There's just the shaft of the screw up the hole, looks like someone has tried to drill it out perhaps to try to use an easy-out. I tried that too but it isn't cooperating and I reckon I'll damage the body of the cylinder further if I try again.

Anyway the job is now to replace the master cylinder. I guess this can be done with the brake lever left on (hope so 'cos it aint coming off...)? Any advice?

 

[Disaster Area]

The only advice I have is to read the manual, search YouTube (a guy called Chris Harris has some useful ones) and then take it slowly when you're in the mood for fettling. Personally I schedule in time for copious cups of tea!

Let us know how you get on.

 

[kennyc]

buy a new master cylinder and pivot pin and drill the old one out once its off the bike

 

[DrFarkoff]

The "head" is an allen socket on the top side of this bolt Its part 5 in this diagram LINK

What you have is an alloy bolt with a nylon liner (part 6) all that is broken off is the end of the bolt and its locknut

Locate the allen socket on the top and just try an allen key to undo the remains of the bolt

If its rounded out?? CAREFULLY tap in a spline or torx bit in to the socket get someone to hold a bit of round bar or a big chisel (something weighty) that you can get to make contact with the bottom end of the bolt Whilst you tap in the chosen implement above

Number one before you try the removal Take off the brake fluid reservoir cap and remove the fluid, a syringe is good for this and you can get them in the vets, or chemists or my chosen preference the farm supply shop Remove the plunger and coat the rubber bit with rubber grease (If you have a BMW bike in the garage you should ALWAYS have this in the Garage)

Number 2 undo that Brake pipe and move it away from where you are working

Number 3 refit reservoir cap

Number 4 on the front underside of the switch gear you will see a phillips screw head remove it and keep it safe you can now remove the switch gear and refit screw in the mount (trust me on this one!!)

Number 5 with a 4 mm allen key slacken the allen bolt at the lower side of the mount and swivel the assembly so that the bottom is now nearly pointing upwards Something nags me that you can't turn it completely upside down but I can;t recall what just now)

Number 6 get a small screw driver and see if you can GENTLY remove the brake switch screws if they are tight leave them be!!!!

Now get a kettle of boiling water and TRICKLE it over the area keep trickling until the alloy is too hot to touch and start to apply pressure on your allen key or whatever tool you are using

This will do 2 things it will heat the alloy up reducing the strain on the bolt and dissolve salts around the threads / pivot that have resulted from the weeping seals and "may" also dissolve" the salts on the wee switch screws enough to let them turn now and you need to wash the area well before you fit the new plunger anyway

From memory you will only need to screw it back about 5 or so millimeters then its a push fit through the brake lever (can be tight due to the salts again)

There's one 3 mm allen key on the inside of the cylinder once you remove that the piston assembly will pop out Go easy on it when refitting the smaller components a "guesstimate" or torque is an eighth of a turn from when you have to use force on a tool

N.B. a Trick for you to prevent the fluid damaging any paintwork Spray it liberally with "back to black" or furniture polish or vegetable oil spray

Any fluid spilled should be rinsed away with water as its harmful to animals and small children

Hopefully that's all useful and you are not bored to tears but it'll take less time to read my explanation that to listen to that twat Chris on you tube!

 

[DrFarkoff]

To bleed it ...Just reassemble the bits in reverse order

BEFORE you fit the plunger there are 2 holes in the base of the reservoir make sure the little one is clear something like a FINE sewing needle its a really small hole and you don't want to bur the alloy you just want to open the passage

A tip I forgot to give above get a wooden dowel and cut a slot vertically down it at one end about an inch long

get a sheet of 1000 Wet and Dry cut a strip about 6 inches long and 3 inches wide and fold it over and slot it in the dowel and turn the dowel in your hand so the paper folds around the dowel

Stick it in your battery drill or mains drill but keep the speed down, wet it with soapy water and you have a cylinder hone run it up an down the bore about 6 times and you should have a clean scratchless chamber that once washed out, wont damage the new piston seals

Once rebuilt and the correct way up etc refill the fluid and flick the brake lever about 5 mm fairly quickly You should see a stream of bubbles out of the little hole

once you start to get lever pressure just hold it for 5 seconds and release and when the bubbles stop you should have a cracking brake lever

Long and Drawn out? Well that's what you give people money for and you can now see what we actually do to earn money!
Make sure and blow out all the water type stuff with an airline

 

[ajd]

Brilliant - thanks for taking the time to type all that! Better than the Haynes manual by miles. I will give it a go.

 

[ajd]

DrFarkoff -
At what point does the top of the brake lever pivot bolt become visible? It looks to be entirely hidden underneath the reservoir. I can't see how I will get access to the allen-head of the broken pivot bolt.