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-   -   Anyone have tips or info on rebuilding PM rear master cylinder (http://www.clubchopper.com/forums/shop-talk/111911-anyone-have-tips-info-rebuilding-pm-rear-master-cylinder.html)

1993SSP 05-19-2015 09:32 PM

Anyone have tips or info on rebuilding PM rear master cylinder
 
Anyone have any tips or info on rebuilding a PM rear master cylinder 11/16... I got mine apart and went to go back together with it and the seal on the plunger does not seem to want to go back in.. I am afraid of tearing them, I looked on line for some detailed instructions but could not find any

ecir45 05-19-2015 09:43 PM

try wetting it with some brake fluid if you haven't.

pushrod243 05-20-2015 08:30 PM

yes use brake fluid as a lube.
Dot 5

1993SSP 05-23-2015 08:14 PM

Ok,, finally got the rear master cylinder rebuilt today,,, bench bled and on bike,,, after that it's still not bleeding,, I am using a banjo bolt/brake light switch with a 45 degree fitting and stainless line... checked line and fittings for clogs to be on safe side since they were with the roller when I bought it and they all are clear... HERE is where I am at with the diagnosis... I can unhook the line at the caliper and no fluid would come out of the line by pumping and with a mighty vac..... so I moved onto the master cylinder end.. I unhooked the line and there would barely be a drip of fluid come from the fitting.. I can loosen the banjo bolt and fluid flows out easily... I tried 2 different fittings with the same banjo bolt and got the same result...


has anyone got any suggestions??? Is it possible that the banjo bolt/switch is the problem?

Shovel52 05-23-2015 08:45 PM

You are saying that you did bleed the master cylinder?...does it squirt when you pump it???-
if yes then did you try cracking at the brake light switch and pump the air out..actually pump first and then crack..sometimes that will do the trick....crack at each joint and pump and then finish at the caliper with your vacuum

1993SSP 05-23-2015 08:54 PM

Ok,, I'll give it a try... With the banjo bolt completely out it pumps and has fluid coming out fine but after I put the banjo bolt and fitting on I get at most just a small drip,, I've never had problems like this before on brakes,, it's definitely tested my patience

STEINBVG 05-24-2015 06:07 AM

Try a regular bolt instead of the that switch bolt. See if you can bleed .

Also if you look on the bolt , it has a recess which should be within the banjo fitting. That allow the fluid to flow. If it,s misplaced/ mismacnined, it will close the pass. I used at times 1 copper washer on one side of the fitting and 2 washers on another to allign the passages.

Overall, I hate hydraulic switches, they all go bad eventually, initially it takes more hard braking to make the light come on and afterwards nothin ( diaphragm gets stuck) -although the you still have brakes, but no light comes on.

From now on I will use something like this- I did it on my last builthttp://www.clubchopper.com/forums/pi...ictureid=12808
It,s a mechanical switch with when compressed, the light is off. It,s placed behind my foot pedal on a little bracket made of an angle. When it moves towards master and frees switch, the light comes on. Easy to adjust to a slightest move.

1993SSP 05-30-2015 07:09 AM

This thing is about to drive me insane...:whacked:

I have pumped and bled and still no good pressure,,, no leaks anywhere that I can find.. there are no longer any air bubbles coming out of the bleed screw but after pumping the pedal there is still constantly tiny bubbles coming up in the resevoir.. does not matter how slow or how fast the pedal is pumped the air bubbles come up in the fluid....


suggestions?

STEINBVG 05-30-2015 08:18 AM

Quote:

Originally Posted by 1993SSP (Post 1261104)
This thing is about to drive me insane...:whacked:

I have pumped and bled and still no good pressure,,, no leaks anywhere that I can find.. there are no longer any air bubbles coming out of the bleed screw but after pumping the pedal there is still constantly tiny bubbles coming up in the resevoir.. does not matter how slow or how fast the pedal is pumped the air bubbles come up in the fluid....


suggestions?

We have given the suggestions, but I,m not sure you have tried them...
I,ll try again:
If you remove the line from the master and do the "finger test"- press against the finger, does it fill like it,s pumping? You,re sure you have assembled the master correctly?
have you tried to remove the break switch bolt and substitute it wi a regular, just as a test as a had mentioned before???

Shovel52 05-30-2015 09:20 AM

It sounds like you are ok up to the banjo bolt...and have lots of air in between there and the caliper....you will never bleed....take a good look at the banjo bolt and see if you can find an image...google images...and see if there are any differences....in banjo bolts ....maybe you can modify......or detect the problem there... worse case scenerio is eliminate the banjo and go straight to the caliper and use the electrical switch as Stein mentioned.......note I just looked at images and there are differences in depth on banjo bolts...make sure holes line up...some line person could have screwed up......that has to be your problem....

STEINBVG 05-30-2015 11:14 AM

Quote:

Originally Posted by Shovel52 (Post 1261108)
It sounds like you are ok up to the banjo bolt...and have lots of air in between there and the caliper....you will never bleed....take a good look at the banjo bolt and see if you can find an image...google images...and see if there are any differences....in banjo bolts ....maybe you can modify......or detect the problem there... worse case scenerio is eliminate the banjo and go straight to the caliper and use the electrical switch as Stein mentioned.......note I just looked at images and there are differences in depth on banjo bolts...make sure holes line up...some line person could have screwed up......that has to be your problem....

Yep, I use at times double banjo bolts, have to be careful to allign all the passages so the fluid flows.
So if master pushes fluid- you simply follow the line where it stops pushing out.
Either restrictions or still air in the system.

By the way, having tiny leak of brake fluid doesn,t prevent to achieve . I would have brakes and see at times wet typically around banjo/ washers. Retighten or change to new washers. Till dry.

1993SSP 05-30-2015 12:59 PM

The master cylinder is built correctly,, Performance machines sent me a diagram...

I am off to get some new banjo bolt washers .. the ones I had were used and looked good but I am suspect of them.....

thanks to everyone for the suggestions,, they are greatly appreciated!

STEINBVG 05-30-2015 02:38 PM

Quote:

Originally Posted by 1993SSP (Post 1261116)
The master cylinder is built correctly,, Performance machines sent me a diagram...

I am off to get some new banjo bolt washers .. the ones I had were used and looked good but I am suspect of them.....

thanks to everyone for the suggestions,, they are greatly appreciated!

Use copper ones, and nothing else. They are the best.

Shovel52 05-30-2015 07:32 PM

Maybe it is the amount of washers or thickness that is causing the misalignment, you might experiment with some thickness if you are still having problems...

1993SSP 05-30-2015 08:47 PM

I looked over my line closely after installing new banjo washers (all copper as suggested) and trying to bleed again with the same results.. nothing but fluid and TONS of air bubbles.. I noticed in the clear covering I could see some purplish tint to the line, the DOT 5 fluid I am using has a purple color to it


I'm ordering a new line to put on and see how it goes from there...


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