Topic: When compressed air ain't enough..

[nvr2old]

I've had my '72 Honda XL250 cafe' in long term storage for the past six years.  I went to great lengths to make sure when I decided to take it out of hibernation, it would require little to get it going again.  Everything is great..until I went to grab the front brake, which is a front end off of a CB550 with a single disk.  The pad is seized in the bore.  No problem, I'll just take it off, hit it with some compressed air..pop..clean, re-assemble..um..wait..air ain't budging it..now what..?  I've tried a bit of heat and a little tapping to see if it will loosen, but no go.  I have it sitting with some penetrating oil as I type..any other words of wisdom that might help?  I appreciate it.

[754]

Nice XL. You can get piston out using grease gun adaptor..

[nvr2old]

Grease gun adapter..hmm.  Interesting.  Can you elaborate..?

[754]

Find a bolt that fits the threads, 10 x 1.25 I believe, drill and tap head fir grease fitting.
Now pump it full of grease..

[nvr2old]

Ahh.  Thanks very much.

[scunny]

grease gun works a treat, I was able to just start the tip of mine in the thread and pump away.

[Scott S]

 Pep Boys, etc., sell grease fittings. I found a multi pack that had one with the right thread. Screwed that in and used my grease gun to push out a stubborn one.

 If it's that stuck, plan on getting a new piston and seal.

[nvr2old]

Thanks for tips, gentlemen.  Finding a zerk that will screw into the threads would be nice.  I'm hoping once it's apart I can just clean and reassemble, but if it needs new seal and piston that's doable.  I'll let you know what happens.  I'm itchin' to ride it again.  It's a fun little beasty. 

[eigenvector]

Doesn't need one.  The threads are close enough that the standard one will fit - just don't get heavy handed screwing it on, it only needs to stay there long enough to push the piston out.  and it WILL push that piston out.  Plan to spend the rest of your life cleaning grease out of the caliper.

I had to resort to this tactic when I did the same thing - didn't think it would work either, oh yes it does...

[PetesPonies]

How much air pressure did you use? I've never had one where air pressure wouldn't do it and I'm talking car calipers.

[754]

If 1500 psi cant get it out...what will..
And as I say, if 150 psi or less of air got it out...it wasnt stuck..

I have never heard of any injury using the grease gun.

[eigenvector]

the problem with using air is that when it gets unstuck it will exit the caliper like a bullet.  I mean that literally too.

That's the nice thing about grease - it comes out nice and slow.

[PetesPonies]

You wrap the caliper with a towel. You pack the towel between the piston and the other side of the caliper and then wrap everything. You still have the hose in place.It sounds much harder than it is, because it isn't difficult at all.The towel will catch the piston, there is no danger. Ifyou are mechanical, this is easy. If you hurt yourself, you are not 

[pjlogue]

If you ever have the problem again try unbolting the caliper but keep the hydraulic lines intact and pump it out.  If that doesn't work then get the grease gun.  Air works most of the time but you can do some damage to the puck or anything near by if you don't contain it.

-P.

[754]

You wrap the caliper with a towel. You pack the towel between the piston and the other side of the caliper and then wrap everything. You still have the hose in place.It sounds much harder than it is, because it isn't difficult at all.The towel will catch the piston, there is no danger. Ifyou are mechanical, this is easy. If you hurt yourself, you are not 

You wrap the caliper with a towel. You pack the towel between the piston and the other side of the caliper and then wrap everything. You still have the hose in place.It sounds much harder than it is, because it isn't difficult at all.The towel will catch the piston, there is no danger. Ifyou are mechanical, this is easy. If you hurt yourself, you are not 

You wrap the caliper with a towel. You pack the towel between the piston and the other side of the caliper and then wrap everything. You still have the hose in place.It sounds much harder than it is, because it isn't difficult at all.The towel will catch the piston, there is no danger. Ifyou are mechanical, this is easy. If you hurt yourself, you are not 

You wrap the caliper with a towel. You pack the towel between the piston and the other side of the caliper and then wrap everything. You still have the hose in place.It sounds much harder than it is, because it isn't difficult at all.The towel will catch the piston, there is no danger. Ifyou are mechanical, this is easy. If you hurt yourself, you are not 

Pete your warning here is essential to recommending air..often no warning is given.
But as I said before ....if normal air pressure moves it..it was not stuck.

[nvr2old]

If you ever have the problem again try unbolting the caliper but keep the hydraulic lines intact and pump it out.  If that doesn't work then get the grease gun.  Air works most of the time but you can do some damage to the puck or anything near by if you don't contain it.

-P.

This was my first technique, and it didn't budge, sadly.  I put 150psi from my compressor to it and it didn't move it a bit.  I've done it this way many times and by wrapping it in a towel it catches the piston fine with no injury.  The pop scares the crap out of you but it's expected and I wait for it.  I'm still a bit unclear on the grease gun technique. Scott S recommends using a screw-in zerk and eigenvector says one's not necessary (?)  Are you talking about attaching the grease gun tip to the bleeder?  Maybe I'm misreading.  I can understand if one can be screwed into the hard brake line threads and then a grease gun to fill and push the piston out.  Sorry to sound like such a newb.  I would rather not have to fill the caliper with grease because of the cleanup involved, but if that works, I'm willing to give it a try.  Argh..have to go buy a grease gun, though..  I've always used the palm pump kind for swing arm bushings and such.

As Dr. McCoy would say, Dammit, Jim, I'm a painter not a brake mechanic..

[754]

Some say that you unscrew part of the tip on gun and it fits..sort of.
 I just took 9/16 hex steel and machined it, including a proper seat in it..not needed in a MC.
 The bolt is within the scope of most folks.

I opened quite a few sat out in the open weather in the boneyard calipers..
 Sometimes you have to work a few minutes wiping out the grease..other times its not sticking due to the brake fluid .. At any rate. A blob the size of the piston... Is what we are talking about...but hey..it works..

[nvr2old]

Thanks again for the advice.  I appreciate it.  I'll get it done.  Not gonna let a measly brake caliper get the best of me.  I have a Tiddler Tour on Vashon Island to attend next month, and this is the bike I wanna ride for it.

[seanbarney41]

Grease gun never fails, everything else might.  No need for special fittings 1 thread finger tight gets it done. 

[drumstyx]

You should be able to get the grease gun on the bleeder valve...that's what I did the first time I rebuilt a caliper, though it wasn't seized.

[PetesPonies]

Well I think 150 psi is a good amount. And I believe when 150 gets it out,. it's stuck. I have had non functioning calipers that 150 PSI popped them out. But I spray them with lube and I will hit the sides with a hammer if needed,. while the air is supplied. A good non-leaking pressure is important.

[TwoTired]

I've always gotten the caliper piston out using hydraulic pressure from the hand lever master.  Bleed the front brake and squeeze the lever.  Pumps the piston out.  Hasn't failed me yet.

[754]

1500 psi trumps 150 psi every time..

[PetesPonies]

Pistons are not normally stuck "in". So if it is difficult to remove, try pushing the piston in, along with some penetrating spray. This may allow it to now come "out". There's little tricks that work. As I said, one has never not come out for me. They might need some persuasion . . .

[754]

Lucky you.. Try salvage yard stuff outside rain snow year after year.
 I had a small machine shop, when people couldnt get it  out with air, they brought it to me.
I suspect aluminum calipers, grow far more corrosion than cast iron calipers..

Like the subject line in this thread, and I said, we were dealing with stuck ones.