Master Cylinder Replacement and Bleed

SunnyJim

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A few questions on new MC I bought. Bleeding the brakes and can't seem to get all the air out of the lines. I saw a video where each cylinder was blead separately because air would get caught near the wiring for the brake light vacuum. Has anyone had this issue. Seems to be a lot of work. I'm using a bleeder from harbor freight but can manually pump brakes if needed.
IMG-1699.jpg
 

redflash

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there are times that "air in the lines" is not the problem. I missed this and others have also. Calipers and rotors must be matched.
The suppliers sell lists of calipers, is you look closely they will "sometimes" say .......for 1/8 inch rotor.....for 3/16 inch rotor. and so on.
I picked a larger diameter rotor for it's stopping power.....not for it's specific thickness.
I bled and bled until I was blue in the face.....then I bought several different bleeders.....nope the brakes still didn't grab.
The reason.......the rotor was 3/.16 inch and the caliper was 1/4 inch......never going to grip, and it had nothing to do with bleeding air.
Solution.....I welded a thin washer to the back of each puck, reinstalled them, and the extra thickness brought the shoes into contact with the rotor.

Voila brakes work....Kart stops

Da redflash
 

Snaker

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I've had difficulties with those small systems as well.
I have a air powered pneumatic bleeder setup that works great on every thing else.
What I found is that when filling a troublesome system, don't worry about bleeding at first.

Open the bleeder, put a hose on it or at least drape a rag over it.
Fill the MC and start making solid/full strokes on the brake control, with a half second between each to make sure the MC refills fully.
Just leave the bleeder open and keep at it till fluid comes out of the bleeder.
Maybe a couple more pumps to purge large air bubbles at the caliper.
Your moving a lot more fluid that way than during the bleeding and can move bubbles through the system better.

Once you get that done, then do the bleeder thing.

My setup was strong enough to pull a good quantity of fluid and could pull small bubbles downhill.
A hand setup might not be able to do that.
Sometimes it helps to position the machine at different attitudes to move troublesome bubbles.
 

SunnyJim

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I've had difficulties with those small systems as well.
I have a air powered pneumatic bleeder setup that works great on every thing else.
What I found is that when filling a troublesome system, don't worry about bleeding at first.

Open the bleeder, put a hose on it or at least drape a rag over it.
Fill the MC and start making solid/full strokes on the brake control, with a half second between each to make sure the MC refills fully.
Just leave the bleeder open and keep at it till fluid comes out of the bleeder.
Maybe a couple more pumps to purge large air bubbles at the caliper.
Your moving a lot more fluid that way than during the bleeding and can move bubbles through the system better.

Once you get that done, then do the bleeder thing.

My setup was strong enough to pull a good quantity of fluid and could pull small bubbles downhill.
A hand setup might not be able to do that.
Sometimes it helps to position the machine at different attitudes to move troublesome bubbles.
Thanks so much. I will try this.
 
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