Master cylinder issue on Pan....

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OLD WUN
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Master cylinder issue on Pan....

#1

Post by OLD WUN »

Just took rear master cyl off muddy inside but no rust in cylinder. Cleaned up all nice and looks like first time of rebuild, low mile bike. Put the kit in and piston is stuck half way down. Finally got it out, measured size against the old one and almost same. Put old piston in with new rubbers and it stuck. Never needed to hone the cylinder as it was nice. Wonder if now I should as it has me wondering. Can't leave it on the bike that way. Any thoughts???
OLD WUN
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Re: Master cylinder issue on Pan....

#2

Post by OLD WUN »

I should add that I have done at least 5 old car master cylinders in the past so this is not my first, but never seen one stick like this. I lubed the assy up with brake fluid to make sure it was nice and smooth as usual and so I am at a loss.
Bigincher
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Re: Master cylinder issue on Pan....

#3

Post by Bigincher »

My only thought is, perhaps a light honing would free it up.
If the piston is OEM and serviceable, I would always choose OEM over aftermarket.
59Panman
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Re: Master cylinder issue on Pan....

#4

Post by 59Panman »

Not sure if this might be part of your problem. On my stock master cylinder, the tiny pin size hole for the fluid return plugged with a piece of crap and my rear drum would lock up. I took a tiny piece of wire and dislodged the crap plugging the hole, which released the hydraulic pressure on the rear brake shoes allowing the drum to turn.
OLD WUN
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Re: Master cylinder issue on Pan....

#5

Post by OLD WUN »

Thanks for the input. I did clean the ports but will check again. My car hone is too big so will see if I can come up with something to do a light hone of the cyl. I had to use air pressure to get parts out the last time. Today is a new day and sometimes things look different so hope to get this resolved.
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Re: Master cylinder issue on Pan....

#6

Post by Andygears »

I made a master cyl hone from 1/2 inch CPVC pipe with a slot & 400 or 500 sandpaper in the lathe spindle. Just like a Sunnen hone ...kinda.

My 2 cents
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Re: Master cylinder issue on Pan....

#7

Post by Wrong Road »

I just ordered a 20mm flexible hone for cleaning out my Zel master cylinder. Less than $7.00 plus shipping! Haven't used it yet, will report back later. Has anyone used one of these? http://www.travers.com/honing-tool/p/53-800-244/
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Re: Master cylinder issue on Pan....

#8

Post by Bigincher »

I have used a 'ball hone' before. They are primarily used for breaking the glaze inside cylinders, not so much for material removal. It's worth a shot, I'd try it.
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Re: Master cylinder issue on Pan....

#9

Post by james »

Yes, as Bigincher said we call them "ball hones" they do a nice job. Try it.
Thanks for the tool site info.

Jim M
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Re: Master cylinder issue on Pan....

#10

Post by Wrong Road »

Thanks for your advice; Ball hone seems to have worked well. Before and after pictures attached. After 10 seconds, still some discoloration on the cylinder. Ran it an extra 5 seconds and cylinder is clean as a whistle. Popped in J&P rebuild kit; seems okay. I will add in the lines and bleed the system and hope all will be well. My 1960 FLHF is taking shape. Sent the metal out for paint. Just need to add engine and gearbox. Has been in boxes for 17 years so getting excited to hear it and see the flames again!

Image
Image
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Re: Master cylinder issue on Pan....

#11

Post by Wrong Road »

Picture of 1960 FLHF so far. Didn't fit with last post.

Image
OLD WUN
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Re: Master cylinder issue on Pan....

#12

Post by OLD WUN »

Since this thread is still alive I will follow up. I showed a HD tech friend my issue and he said to just stretch the spring out a lot and sure enough it works great now. How simple is that. :idea:
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Re: Master cylinder issue on Pan....

#13

Post by Bigincher »

Bike looks good. Just bolt a couple more things on, and you're down the road...! :wink:
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Re: Master cylinder issue on Pan....

#14

Post by talldrifter »

Hope this is not a hi jack, same problem, different manufacturer. I have a GMA rear master and type "A" rear brake set up, came without rubber gator, dirt and grit got in and caused leak past seal. Ended up buying new rear master, mounted and filled with fluid, promptly stuck half way while trying to bleed. Had to pull brake lines and use a drift and soft hammer to get it out. Couldn't find anything obvious wrong with cylinder, new piston is all black but old piston is bare aluminum where it might touch inside of bore. Old piston measured slightly smaller using a one inch micrometer. The piston has a tail that sticks out that the push rod connects to, so I chucked the tail into my drill press, set for the slowest speed and held a fine flat file against the parts that made contact with the bore. After carefully removing the black coating and a small portion of aluminum, with several trial fittings, it now works flawlessly. Just my home shop solution, maybe it will help someone with a similar problem.
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Re: Master cylinder issue on Pan....

#15

Post by Bigincher »

I think that's called a "vertical lathe". ;)
Sometimes we just do what we have to do.
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