Front brake master cylinder disassembly?

[B0000M]

brakes on both my cr and crf are spongy even after bleeding every which way possible - incl holding caliper above master so air goes up, it gets to a spongy point and doesnt get any better, ive decided to try replacing the seals in the master cylinder.

so- how do i get the plunger to come out? is there some trick or something hidden i need to do? or do they even come apart at all?

[theblacksmith]

Hi mate - plunger should have a wee circlip holding it in. Remove this and washer and whole plunger should slide out. Have they become spongy gradually or all of a sudden?

[B0000M]

Hi mate - plunger should have a wee circlip holding it in. Remove this and washer and whole plunger should slide out. Have they become spongy gradually or all of a sudden?

both bikes were 2nd hand, and both have been pretty shit the whole time ive had them, the crf is the worse one. ive got identical bikes of mate's sitting beside them in my shed and they dont have the spongy problem so i know thats not how they are meant to be.

ok, i didnt want to pull too hard on the rubber cover thing in case it wasnt meant to come off, the circlip must be beneath that.

[theblacksmith]

Yep - circlip is beneath rubber boot(which should be supplied with new seal kit hopefully).
If youre still getting spongey brakes after - try reverse bleeding- inject fluid up from caliper bleeder till it comes up to level in lever reservoir.This way you can look out for any air bubbles as well.You will need a veterinary syringe and piece of clear piping. Best of luck - I have to change my steering head bearings today.

[barty5]

Yep - circlip is beneath rubber boot(which should be supplied with new seal kit hopefully).
If youre still getting spongey brakes after - try reverse bleeding- inject fluid up from caliper bleeder till it comes up to level in lever reservoir.This way you can look out for any air bubbles as well.You will need a veterinary syringe and piece of clear piping. Best of luck - I have to change my steering head bearings today.

s/head bearing are allways fun getting the race off the stem with out a press is the best part.

[barty5]

both bikes were 2nd hand, and both have been pretty shit the whole time ive had them, the crf is the worse one. ive got identical bikes of mate's sitting beside them in my shed and they dont have the spongy problem so i know thats not how they are meant to be.

ok, i didnt want to pull too hard on the rubber cover thing in case it wasnt meant to come off, the circlip must be beneath that.

youll have to let cheese know of the out come or what ever ends up fixing it he can added it to the list of things to do.

[imdying]

ok, i didnt want to pull too hard on the rubber cover thing in case it wasnt meant to come off, the circlip must be beneath that.Often that external rubber boot has a metal ring built into the base which makes it an interference fit to the body. Usually levering it out with a dulled flathead screwdriver works a treat.

[B0000M]

he;s been complaining about that for about a year now!

[cheese]

The entire thing (forgot name of the piece that pushes in and out of the master cylinder) is like $70.

[dammad1]

s/head bearing are allways fun getting the race off the stem with out a press is the best part.

I did mine last week but the shop lent me the tool to get them out which makes it a 20 second job.

[barty5]

I did mine last week but the shop lent me the tool to get them out which makes it a 20 second job.

Yeh i was havin a go at home couldnt be bothered drivin in to workshop ended up drivin to workshop much easyer with the right tools. Pissed off wife as she could go out bike in bits all over court yard till i got back.

[krad_nz]

brakes on both my cr and crf are spongy even after bleeding every which way possible - incl holding caliper above master so air goes up, it gets to a spongy point and doesnt get any better, ive decided to try replacing the seals in the master cylinder.

so- how do i get the plunger to come out? is there some trick or something hidden i need to do? or do they even come apart at all?

KTMBoy showed me a neat trick at the sandpit the other day.
Kneel down beside your front wheel. Press your knee into the front caliper and hang onto the wheel for leverage. You're essentially trying to compress the caliper from the outside. This forces air out of the caliper area etc. Do this a couple of times. After compressing the caliper a couple of times you will need to pump up the brake again via the lever.

My KDX always had a really soft front brake. I had bleed the system, even tried reverse bleeding with a syringe but nothing really helped. This took about 5 sec to do and made a massive difference. The braking is still mint now. Try it!

[cheese]

Ooh I'll give that one a crack I think.

[theblacksmith]

Did u manage to get the spool/plunger out of master cyl BOOOM?

[B0000M]

Did u manage to get the spool/plunger out of master cyl BOOOM?

havnt yet, i pulled the rubber cover bit out, found out my circlip pliers arent small enough and thats as far as i got, but i can see exactly how it does come out

[theblacksmith]

No one will be able to keep up with you after you fix your brakes mate.

[BigGuy]

The tool your looking for is called internal circlip pliers. I find the angled ones are the best for extraction and the straight ones best for putting the clip back.

[B0000M]

yea ive got internal circlip pliers, just the pointy ends arent pointy enough.


problem fixed

the adjuster bolt on the lever that adjusts freeplay had a thickish nut on it (on both bikes) compared to the other 2 bikes in the shed which had thin nut or just a washer - after removing this excessive freeplay the brakes feel the same as the good 2 bikes.

now theres 4 bikes in the shed with good brakes, 7 radiators and 3 shocks.......

[tommorth]

I had similar fix for my ktm a bit of solder in betwen the adjuster and the m/c piston and great brakes before bit soft and only worked after pulling them in halfway and no they dont drag now