front brakes

Hey all need some help here...

Front brakes try to lock up when I push the bike backwards. Makes for a very hard time to get it to back up even a few steps, you cannot do this sitting on the seat at all. Seems to go away after riding a cpouple of blocks then does it again when you try to back out of a parking spot.

Bled brakes and loosened bolts to move them around and no help so far so I let some pressure off and still trys to tighten when I push backwards on the bike..

1982 750 Seca with dual front Disc brakes.

 

Are you 100 % sure it is the front brakes?
Have you tried popping out the pads and seeing if it still persists?
Or lifting the front tire off the ground to see if it does it when you rotate it backwards by hand?
Just want to confirm it's not some other component.

 

Sounds like you might need to rebuild your calipers. See this thread.

 

Got the Calipers off and it looks like one is stuck...Managed to open it up a tad and I will try to work it back and forth a few times to loosen it. I used some liquid wrench on the piston and carb cleaner etc.

 

STOP right there. If you're using liquid wrench or carb cleaner trying to get a caliper piston unstuck, you are:

A: Wasting your time.
B: Asking for a bad situation to get worse.
C: Trying to take a shortcut in a situation where shortcuts aren't allowed, ie: brakes.
(All of the above, by the way.)

You've got a couple of brake calipers to rebuild, and probably a master cylinder that needs attending to. These are your front BRAKES we're talking about, your LIFE depends on them. No shortcuts allowed here; it's not difficult just a pain.

 

dont use carb cleaner or brake cleaner the only thing you see is the dust boot carb cleaner will eat up the rubber . i dont recomend it but if your going to try to free it do this get a c clamp run it in to it just about touches the piston pull the brake lever it will move the piston out crack the bleeder then try to push the piston back in with the c clamp the reason your cracking the bleeder is any grunge that cones off the piston and gets in the fluid will go out the bleeder instead of going back into the line keep doing this topping off the fluid in the mc til it works correctly cover up any painted parts that the mc might drip on so it wont eat your paint. ive been lucky doing but usually they arent completely stuck but i take my time you do run the risk of the seal starting to leak but it doesnt work the way it is now. the right way is to rebuild it but you have to do what you have to do . if your caliper is stuck badly this will not work

 

How do you get the pistons out?

I can push them in, but, don't they have a spring to keep them 'loaded'?. They do not slowly come back out like on a car.

I can order the rebuild parts after I figure out how to take them apart.

 

pump the brake lever will pop them out pretty quickly brakes dont use springs to keep loaded when you back off the pressure it stops clamping down if it had springs you would wear pads out very quickly

 

I forgot to add, they are not on the bike..they are on the bench

 

you can use air usually

 

Block the pipe union hole with a plain bolt.

The bleed screw is the same shape as a grease fitting. Open the bleed screw, attach your grease gun and get pumping. It will push the piston out; this method works even when compressed air won't. It is a tad messy though.

 

"grease is a tad messy"....BUT much safer!

 

Is it ok to have your caliper loaded with grease?

 

You have to clean it out anyway.

The grease forces the piston out slowly, and for sure. You can use compressed air; however I run 100psi in my tank and have never had any luck. I've used the grease trick twice now since I heard about it, and it works great.

 

Well, my luck runs true..the bleed valve is larger than a grease zert...can't get a good seal for air either. I guess I will be making a brass adapter for air. Or finding a grease zert to fit. meanwhile no new cruising for Davey this week.
On the good side, the Steaks are defrosted and the beer is cold.

Come on over.

 

a rubber tip air nozzle works pretty good a must have when you rebuild carbs if the piston is in really rough shape you will probably have to use grease good luck

 

Try loosening your grease gun tip a bit. It'll fit then. Just unscrew the end piece a little until it goes over the bleed screw, then tighten in back down.

 

What are the odds that his pressure relief port in the bottom of his master cylinder, might just be some of the blame if its plugged any? just a thought might want to check that to while your at it :idea:

 

This is wholly symptomatic of calipers that need to be cleaned.

Order NEW Caliper Seals.
The application of the Penetrating Oil may very well have ruined them!

The Calipers Main Seal is seated in a channel.
The channel becomes contaminated with a mixture of Brake Dust, Brake Fluid, Moisture and Road Grime.

The build-up of this foreign matter makes the Seal "Tight" as the build-up makes the normally close-tolerance circumference of the Seal --> "Out Of Round".

The Caliper Piston Seizes ... rather than travels ... and causes the Brakes to bind.

A very thorough Cleaning of the Caliper is necessitated.

 

Looks like lots of people are doing this these days. Here's a recent thread which should help.

 

The grease trick worked great..now they are clean I have to press them back together with a "C" clamp I guess.
Not going to rebuild at this time! Can't afford any $$$ so I will make do with what I have. Was able to remove the seals clean and re-install them using locksmith tools. They look real nice.

Best I can do at this time.

 

You should be able to press the caliper piston back in by hand once the caliper seal channels have been properly cleaned and the seals are in place. If it requires a c-clamp then either you didn't get the channels religiously clean or your old seals are swollen and should be replaced.

New seals are a lot cheaper than the hospital stay will be.

 

Don't try to replace the Caliper Piston ... "Dry"

Use some fresh Brake Fluid from the Bottle and Lubricate the Caliper Bore, Caliper Seal and the Piston.

Without any Fluid in the Caliper and the Bleeder out and the Brake Line Fitting open, ... the Piston will still provide resistance to being pushed-in past the New Caliper Seal.

The Geometry in lining-up the Piston should be perfect on every plane.
If the Piston tilts while being replaced it becomes very difficult to get the Piston to move and you might need to: "Start All-Over" lining it up and inserting it back into the Bore.

A C-clamp, Big Socket and a Quarter will help with stubborn cases.

Protect the Outboard Surface of the Caliper from being scratched.
Tape the Quarter over the end of the Socket with the 3/8 or 1/2 Inch Square.
(Use the Biggest Socket that fits the open-end on the Caliper Piston.)

Keep the Geometry true and Press the Piston home.

 

You said it. Even with the bore squeaky clean, I needed the C-clamp (with a 9/16 socket). That said, closing the c-clamp slowly was very easy with little resistance from the piston. Getting it in straight is pretty important, but also pretty easy - you'll know right away.

 

Used a 'C' clamp and everything went perfectly. It was difficult to bleed the brakes though. I had to add low air pressure with the bleeders open to get it started.
WOO HOO...brakes are just like new. Just test rode and all is well.

Thanks to all who helped and cared for my safety as well.

Dave

 

another success story