Front Master Cylinder Piston Stuck...

...what are my options? I going to try and take the master cylinder apart this weekend to see if I can free things up, but this bike hasn't been driven for over 15 years. So what do you think my options here are? Do I need to get a complete new master cylinder for this or can I get this thing back to a working condition by taking it apart? Let me know what to try.

Likely rusted swollen steel piston that has also pitted out the Al bore.
If so no recovering it but re sleeve.
Might try to boil in vinegar [weak organic acid] or
the stronger phos acid rust solutions.
Tap into piston to tread a puller, pressurize from behind
or beat snot out of it slamming on wood block.

If master cylinder is stuck up, I can only imagine what
you face down below. Just getting cap off is murder
enough, then may face rusted in place pucks.

hobot

After soaking in penetrating oil or using Hobot's idea of boiling in vinegar I wonder if you could hook up a grease gun to the brake line fitting and pump it full of grease (like has been done on many calipers).

Did you search the forum? Good stuff here.

Well, I got the master cylinder off and the piston is stuck real good, so I'm thinking I want to replace it. Any suggestions as to a good resource for a new/rebuilt front master cylinder?

Also, there are signs that there is rust in the brake line and the inlet of the brake light switch. Can this be cleaned or am I looking at replacement of the lines and switch as my only option? I have pulled the caliper yet to see if it is stuck, but will later today.

Kustomizer,

Your very handle implies no short cuts nor expense spent
in order to get your joy ride. I get pensive thoughts flying along
depending on various unknowns to function for max effect.
Rust could indeed collected in hose to matter all the way
to the bottom fitting bore. Swollen inside hoses have
been reported too often. You may face worse in caliper.

Best DIY upgrades I did to 2 Combats that was at least as
good as 13 mm re-sleeved m-cylinder done to Peel special.
1. Remove all restriction -ENlarge rubber cap hole inside m-c bore.
2. SS hose [beware-avoid its chewing tendency]
3. RGM race leverage lever.
4. SS piston and SS caliper pucks.

IIRC, stock ratio is ~17:1, 13mm gives 21:1, moderns ~27:1
Never heard drum brake leverage ratio expressed but
might be revealing to know.

hobot

Do you want to keep the stock appearance?

Your choices:

replace with a stock master cylinder
resleeve a stock master cylinder (in which case yours might be usable)
buy an aftermarket upgrade

Most would choose one of the last two. You might as well make some decisions on where you want to go with the braking. Then I am of the school that if you are going to throw something away, you have nothing to lose by getting mean with offending item. Chances are good that if you get that piston out of there that the bore is going to need sleeving anyway. So you might contact somebody like Old Britts and see what they say about refurbing a cylinder with a piston stuck in it. They provide a sleeving service.

Russ

rvich said:

Do you want to keep the stock appearance?

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Yeah, I'd like to keep the bike as original as possible. Do you think Old Britts is the best place to get a replacement master cylinder? I also found one on British Bike Connection and Deluxe Cycle.

kustomizer said:

rvich said:

Do you want to keep the stock appearance?

Click to expand...

Yeah, I'd like to keep the bike as original as possible. Do you think Old Britts is the best place to get a replacement master cylinder? I also found one on British Bike Connection and Deluxe Cycle.

Click to expand...

Get a re-sleeved one then. Looks stock. Works better.

old britts is the place to go. i believe you can send your master to them as a core and they will send you a rebuilt/resleeved unit. get a ss, braided brake line also and investigate the caliper as you'll probably have to send it w/ the master to fred unless you do it yourself. make sure on this! you need good brakes.

rgrigutis said:

old britts is the place to go. i believe you can send your master to them as a core and they will send you a rebuilt/resleeved unit. get a ss, braided brake line also and investigate the caliper as you'll probably have to send it w/ the master to fred unless you do it yourself. make sure on this! you need good brakes.

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Thanks, I will check everything before I contact him. One thing, can I send him the old master cylinder if I can't get the piston out?

More bad news as expected, both front pucks are rusted into the calipers! Are the above suggestions the best to try and free them or will the chemicals damage the finish on the caliper? Any and all suggestions are welcomed.

kustomizer said:

More bad news as expected, both front pucks are rusted into the calipers! Are the above suggestions the best to try and free them or will the chemicals damage the finish on the caliper? Any and all suggestions are welcomed.

Click to expand...

You really didn't use the search...

brake-caliper-teardown-yes-with-pictures-t5458.html

kustomizer said:

More bad news as expected, both front pucks are rusted into the calipers! Are the above suggestions the best to try and free them or will the chemicals damage the finish on the caliper? Any and all suggestions are welcomed.

Click to expand...

Did you get the plug out so that you can see the back of the outter puck? I probably wouldn't put the caliper into something like a bucket of carb cleaner (but carb cleaner might work) but I would hunt around and find something more lubricating and penetrating, then I would figure out a safe way to heat the mixture while the caliper soaked in it. If nothing else kerosene, but again heat it by a method not likely to catch it on fire. I would probably aim my heat gun at it. I also have a waterbed heater I use for stuff like that. Warm helps, it doesn't need to boil. Clean as much of the crap away as you can. There are a number of threads on rebuilding calipers. But I would want to get a look at the bore as soon as possible to determine whether or not further labor was worth it. I would also start shopping on Ebay for another caliper or post an add in the classified section of this forum.

See:

brake-caliper-teardown-yes-with-pictures-t5458.html?hilit=caliper rebuild pictures

kustomizer said:

More bad news as expected, both front pucks are rusted into the calipers! Are the above suggestions the best to try and free them or will the chemicals damage the finish on the caliper? Any and all suggestions are welcomed.

Click to expand...

Assuming you have the outer cover off, you have won half the battle.

First thing you need is Patience.

Start spraying around the caliper pistons with Kroil or better yet make up a 50/50 mix of acetone and ATF and soak the caliper. Just let it soak for a few days then try to push the pistons out.

The outer one is usually the easier of the two...if they're rusted in a bad as you say, they're junk anyway so don't worry about damaging them if you have to get creative to pull them out. On the inner piston I've never had to resort to pumping in grease, a rubber tipped nozzle with compressed air where the brake line connects has always pushed that caliper out for me.

Of course heat will always help. I used to resort to heat right away, but it seems as if each one gets easier to do the more soak time it gets.

*EDIT*
Just went and read the referenced thread. Everything I just posted is darn near verbatim of what has been posted previously.

Ugh, I've had two rusted trapped calipers, did the first one
the tough beat your self up ways and won, but it was not worth
but once to say I did. Last one I knew better and took to
machinist that drilled and tapped threads in outter puck
and sucked it right out with the tap bit, then he drilled
back side of caliper and pushed the inner puck right out
the two bores, then tapped the hole and put a locktited
steel set screw plug in. These were rusted swollen
but did not hurt the bores and needed new seals anyway.

We could have pulled both pucks out the front by
tapping treads in them to pull them out, but thinking
ahead realized with the pusher hole modification
I could do this myself forever more with SS pucks in there.
Set screw don't show unless someone stooping to snoop
and then its a nice beauty mark, not ughly wart.

I anti-sieze goop the caliper cap as never ever want
to injure myself or its two holes again like the first one.
I heat stuff like this to hi temp frying oil level before
any attempt to un-do beyond reasonable strain just
to say I tried.

Your call.

hobot

swooshdave said:

kustomizer said:

More bad news as expected, both front pucks are rusted into the calipers! Are the above suggestions the best to try and free them or will the chemicals damage the finish on the caliper? Any and all suggestions are welcomed.

Click to expand...

You really didn't use the search...

brake-caliper-teardown-yes-with-pictures-t5458.html

Click to expand...

Yeah, I did do a search, but not very well, thanks for the link.

Everyone else, thanks for the input, it's nice to see how different people attacked the same problem.

I wanted to thank everyone for their input on my question about my front brakes. I did successfully rebuild both the master cylinder and caliper! Thanks!