Topic: CB750 Front Caliper stuck, piston seized, really pissing me off

[motomotard]

So after much grunting and impact wrenching i got my caliper apart on my 73' CB750.  Pulled the pads out and i cant get the piston or cylinder out. Wont budge, i tried pumping the lever that dosent do anything. Can i pull it out w/ pliers or will that screw something up?  b/c i pulled on it and it didnt move.  Looks kinda cruddy around there too. The brake was working fine when i took it off.

The fluid in line/screw wont come off either, i got the other one out w/ the impact wrench but cant use that on this one.

Any suggestions or tips?

here are some pics

[jay72chevy1]

yoou pop the piston ot with your air gun.

[motomotard]

i dont have an air gun, how would i do that anyway? i can get one if i need to.

[MrZxp]

The air method works - ensure you have the caliper wrapped in a towel or something, 'cos when that piston comes out it can do some serious damage to anything in it's way...! 

Others have had success with pumping grease via the bleed nipple, try a search of past posts.

Personally, what worked for me was to hook everything back up, fill with brake fluid and just pump away with the brake lever - no drama's or problems only make sure there is a good sized container under the caliper to catch all the fluid when the piston pops out...

Cheers, Phil

[754]

Airgun wont help, brake puts out way more psi..

Try warming it with a torch carefully may help..are you sure m/c is working or can you hook up to another m/c??

[BlindJoe]

Get a grease gun, unscrew the nozzle on the grease gun, put teflon tape on threads of nozzle, disconnect brake line from caliper, slightly screw nozzle of grease gun where the brake line goes (as to not damage threads), squeeze grease gun, your piston comes out, be happy , clean greasy caliper with solvent.

[motomotard]

Airgun wont help, brake puts out way more psi..

Try warming it with a torch carefully may help..are you sure m/c is working or can you hook up to another m/c??

yeah master cylinder should be fine, it was pumping fluid out of the drain bolt and brake was working when on the bike.

anybody got any suggestions for getting the fluid in bolt out?

[Steve F]

Airgun wont help, brake puts out way more psi..

Try warming it with a torch carefully may help..are you sure m/c is working or can you hook up to another m/c??

yeah master cylinder should be fine, it was pumping fluid out of the drain bolt and brake was working when on the bike.

anybody got any suggestions for getting the fluid in bolt out?

You may have to heat it with a propane torch.  Apply heat only to the outside of the thread area, staying away from the brake line, which should expand the housing enough for you to break the fitting lose.  If and when you get the line removed, place a bolt in the hole hand tight only, and put the grease gun on the bleed nipple (be sure you open the bleed nipple first), and pump out the piston.  Since air compresses too much, it won't work except on a free piston.  If you find that the heat alone won't do the trick on the fitting, try heating it up a bit then spray the fitting with a penetrating oil, let it sit a few and try the heat again.

[newcbguy]

does anyone have any suggestions to remove a stuck caliper bolt? the large allen head bolts that hold the 2 halves together? I have one that wont budge and stripped out on me. I heated and tapped on it and it is soaking with PB blaster oil right now, but im not sure how to turn it as it is stripped now. Maybe cut a notch and use a chisel? suggestions?

[Steve F]

does anyone have any suggestions to remove a stuck caliper bolt? the large allen head bolts that hold the 2 halves together? I have one that wont budge and stripped out on me. I heated and tapped on it and it is soaking with PB blaster oil right now, but im not sure how to turn it as it is stripped now. Maybe cut a notch and use a chisel? suggestions?

For something like that, you'd be better off drilling the head completely off, and taking it apart, and wrenching the remainder of the "stud" off with a little heat and penetrating oil.  Use a drill the same diameter as the thread to get the head of the bolt to fall off.

[newcbguy]

Ok,
when I get more time that is my next plan of action. I was able to get the bleed screw out  and hard line fitting and now that single bolt is the only thing standing in my way until I get to the stuck piston 

[OldSchool_IsCool]

Master Pirsig said:

Stuckness shouldn’t be avoided. It’s the psychic predecessor of all real understanding. An egoless acceptance of stuckness is a key to an understanding of all Quality, in mechanical work as in other endeavors. It’s this understanding of Quality as revealed by stuckness which so often makes self-taught mechanics so superior to institute-trained men who have learned how to handle everything except a new situation.

Normally screws are so cheap and small and simple you think of them as unimportant. But now, as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out. With this reevaluation of the screw comes a willingness to expand your knowledge of it.


Now go forth and expand your mind, Grasshopper!

[motomotard]

Master Pirsig said:

Stuckness shouldn’t be avoided. It’s the psychic predecessor of all real understanding. An egoless acceptance of stuckness is a key to an understanding of all Quality, in mechanical work as in other endeavors. It’s this understanding of Quality as revealed by stuckness which so often makes self-taught mechanics so superior to institute-trained men who have learned how to handle everything except a new situation.

Normally screws are so cheap and small and simple you think of them as unimportant. But now, as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out. With this reevaluation of the screw comes a willingness to expand your knowledge of it.


Now go forth and expand your mind, Grasshopper!

nice

[motomotard]

so i got the fill bolt and pipe off. i heated w/ a torch and the thing came right out, cant believe how easy it was. thanks steve F

the cylinder is being stubborn though, i cant even seem to get all the air out of the line, w/ fluid i still cant get it to budge.  i guess ill have to try the grease thing.

[seaweb11]

I second that Nice 

 

Master Pirsig said:

Stuckness shouldn?t be avoided. It?s the psychic predecessor of all real understanding. An egoless acceptance of stuckness is a key to an understanding of all Quality, in mechanical work as in other endeavors. It?s this understanding of Quality as revealed by stuckness which so often makes self-taught mechanics so superior to institute-trained men who have learned how to handle everything except a new situation.

Normally screws are so cheap and small and simple you think of them as unimportant. But now, as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out. With this reevaluation of the screw comes a willingness to expand your knowledge of it.


Now go forth and expand your mind, Grasshopper!

[bistromath]

I just popped one this afternoon. It might help to break the corrosion lock by getting a C-clamp on it and squeezing the piston back into the cylinder a bit. Then get compressed air or a grease gun on it and have at it.

[alltherightpills]

I don't know if this will work on the 750, but to get the piston out of the caliper on my 550k, I disconnected the brake line where the hard line and the rubber line meet up, and then took the emergency tire pump out of my car's tool kit and hooked it up to the hard line.  The end of the tire pump has a clamping mechanism similar to that of a manual pump for a bicycle tire, which made sealing the connection much easier.  I turned it on and watched the pressure rise.  At around 150 or 180 psi, the piston shot clean out.  Cover that thing with a padded rag though, because it shoots hard and sprays grungy, brackish brake fluid everywhere. 

[754]

Shoulda left the steel line in till piston comes out..even if you have to unbolt and hook to m/c on another bike...jm.02

[OldSchool_IsCool]

Master Pirsig said:

Stuckness shouldn’t be avoided. It’s the psychic predecessor of all real understanding. An egoless acceptance of stuckness is a key to an understanding of all Quality, in mechanical work as in other endeavors. It’s this understanding of Quality as revealed by stuckness which so often makes self-taught mechanics so superior to institute-trained men who have learned how to handle everything except a new situation.

Normally screws are so cheap and small and simple you think of them as unimportant. But now, as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out. With this reevaluation of the screw comes a willingness to expand your knowledge of it.


Now go forth and expand your mind, Grasshopper!

A little clarification of Master Pirsig's sayings.  By stuckness, he means running out of options, being stuck on a problem.  It doesn't mean the stuckness of the screw.