07 K-9 Rear Master Cylinder Needed

Energy One
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FrankBDPS

FrankBDPS

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Try Wildsteedworx if he dosent have it get the number off of it and call performance machine. What's wrong with you're old one? they are rebuildable. Good luck.
 
TXCHAD

TXCHAD

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The local shop put a rebuild kit in it but it is still not holding. Cannot find any signs of leaks neither. I will check with Wildsteedworx. Thanks for the help.
 
FrankBDPS

FrankBDPS

Well-Known Member
I would take it back and tell them to fix it right. It's a simple thing to repair.

Is you're master cylinder OK?
 
TXCHAD

TXCHAD

New Member
The mechanic that is working on it has worked on 4 different bikes of mine over the years so I trust his work. He installed a rebuild kit and still doesn't hold. Wildsteedworx is currently closed until July 15th as they relocate their business. I plan to pick the bike up from shop and continue looking for another master cylinder. If locate one, I will have to get it chromed to match bike so it looks like its going to be down for a bit. Thank goodness I got the Vic to ride.
 
TXCHAD

TXCHAD

New Member
After rebuilding, they test rode it and everything was good. They took it out the day I was going to pick it up and the brakes failed again. They bled the system again and appeared to be good. The next day, the brakes had lost pressure again with no signs of leakage.
 
Jwooky

Jwooky

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The MC is so simple. There are two O rings and a cup seal. The housing is very expensive~400-500. Hard to imagine how the plastic piston could damage it.

Sounds to me like someone needs to spend a little more time investigating the real root cause before you spend that kind of money on a housing without understanding why. Did anyone measure the bore? Is the rear caliper ok?

Also I am still confused by your hold language. The brake system does not "hold" pressure. It only is under pressure when applied.
I am guessing you mean, when applying pressure to the pedal, you don't get any force applied to the rotor. If so, what happens? Does it just have no resistance and go to the stop?
 
Marky-Marc

Marky-Marc

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I would check the crush washers first on the rear caliper. Then check the brake line. As everyone says, I don't think it's your master cylinder, could be, but I'm going to say it's your rear caliper. Get some good crush washers.

If the gasket is a little bit off, or you over/under tighten the screws, it will suck air...I've had to put my gasket in a few times to get it right on occasion....

Harley sells some that I love, they have a gasket actually built in the crush washer and I've never had a leak.

They look like this:

image.jpeg


Also, here's a diagram of the master cylinder.

image.png


image.png
 
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Marky-Marc

Marky-Marc

Well-Known Member
a friend of mine welded a big dog cracked rear cylinder and it's still working.

I have a brand new chrome rear master cylinder with full controls, but I don't really want to sell it......
 
Marky-Marc

Marky-Marc

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Here's the rear caliper. Just make sure that there are two crush washer on both ends of the cable, 2 on the rear caliper and 2 on the master cylinder.....

rearcaliper.jpg
 
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