Topic: 750F1 Pad & piston jammed on front brake

[Rnobx67]

Hi guys. I am trying to repair the front brake on a F1 '75 that was stocked with no fluid since.... at least 7 years. first I put some DOT3 in the reservoir.. nothing happened, the master cylinder is stuck. so I disassembled everything, and order rebuild kits for master and brake caliper.

I got success with the pad on the side without the piston and the master cylinder is not jammed anymore (I didn't remove a thing except the lever) with help of wd40.

But the pad and the piston on the other part is not going anywhere.
 I let fine oil, or wd 40 stay in the cavity but there is still no move.

[newday777]

Did you remove the cotter pin on the back and push on the pin?

[newday777]

Back side

[Bodi]

There are 3 common ways.
- get a working master, bleed as well as possible, then pump the piston and pad out.
- Air compressor. Relatively low pressure might work but can make the pad and piston quite speedy missiles plus spit out brake fluid at high velocity. Putting the dead side back on and wrapping in rags is advised.
- Grease gun to the slave piston. Not sure how to connect one to the caliper body but they create a very very high pressure.

[Rnobx67]

Back side

yeah this side I removed it not bigdeal. thanks

[Rnobx67]

There are 3 common ways.
- get a working master, bleed as well as possible, then pump the piston and pad out.
- Air compressor. Relatively low pressure might work but can make the pad and piston quite speedy missiles plus spit out brake fluid at high velocity. Putting the dead side back on and wrapping in rags is advised.
- Grease gun to the slave piston. Not sure how to connect one to the caliper body but they create a very very high pressure.

thank you, good ideas :
1. will try the recently repaired master cylinder with it.
3. if I manage to find my grease gun, but think I need a new one.

thank you @Bodi

[scottly]

The master can create about 300 PSI, but if that isn't enough, the grease gun can do much greater pressures. I've always been able to get the thread on the end of the grease gun's pipe to just barely thread into the banjo bolt's 10mm hole, but others have used a grease zerk with the proper 10mm thread. The gun also works on stuck masters.

[Rnobx67]

I've read that a guy let sink the all assembly in brake fluid, does it seems to worth a try ?

[scottly]

I've read that a guy let sink the all assembly in brake fluid, does it seems to worth a try ?

Nope.

[bryanj]

I always use a grease gun, remove the zerk adaptor and the pipe will screw into the caliper pipe hole approx 1 1/2 turns which is enough, pump away till piston comes out then spend a day or two cleaning the caliper!

[Kelly E]

It's hard to remember to pump the pistons out before I take the system apart. But if they still work it's the easiest way. If I forget I try air next. The grease gun is the last resort.

[BenelliSEI]

I always use the grease gun. Safest and never fails…… years ago I took one of the furl nuts from a used metal line (that screws into the caliper) and drilled/tapped it for a standard grease fitting. Just wind it in, snap on my grease gun and out they come.

[RAFster122s]

Remove caliper bleeder screw, gently thread the hose or pipe from the grease gun in, not forcing it. You don't want to damage the threads. You will get a tiny bit of grease oozing out near that joint. Don't worry about it. Pump caliper full of grease forcing piston out. Scoop out the slug of grease, disconnect your grease gun. Wipe out as much grease as you can. The slug of grease not contaminated can be put in a small container for use on something in the future.
Brake parts cleaner sprayed in the caliper bleeder screw opening and caliper body will remove rest of the grease. Clean the groove for the caliper seal and replace the seal with a new one. Lube that seal with either brake parts assembly lube or red rubber grease or brake fluid.

If you are going to repaint the caliper for this before prepping the caliper for reassembly, of course...
You can cure the caliper paint on the bike if you don't have a small toaster oven you use for hobby stuff (don't use it to warm food anylonger!).

[bryanj]

Screwing greasegun into bleeder wont work as grease will come out of pipe fitting

[Rnobx67]

thank you all, I've tried the master cylinder with no luck. Now I have to find my grease gun (maybe at a friend's place) or buy a new one a give it a try so much counsel for that option and, a lot of hope

[Rnobx67]

I was a little hopeless, BUT I WAS WORKING SMOOOTH, so happy how it works.

[Don R]

 I recently did a couple F1 type calipers, on one I pumped the piston and pad out with a M/C and the other one I did with a grease gun. I only got one thread started but it was enough.
 I scooped the grease out and put it into a spray can cap, now I have some pretty clean grease for whatever use. The original F pad (sometimes?) has an o ring around it that needs cleaned and I lubed it with a film of silicone high vacuum grease too.
 I bought pistons and seals from 4-1, they are K&L brand and decent enough quality.

[BenelliSEI]

Looking at your photos, I’d plan for a new piston. That one looks pretty corroded.

[Tracksnblades1]

I always use a grease gun, remove the zerk adaptor and the pipe will screw into the caliper pipe hole approx 1 1/2 turns which is enough, pump away till piston comes out then spend a day or two cleaning the caliper!

Grease gun will definitely work.  I would only use a hand operated grease gun. Beware of the old air operated chassis greasers that had 5 or 15 gallon grease containers they have a lot of pressure when connected to 150+ air supply.

[Tracksnblades1]

I recently did a couple F1 type calipers, on one I pumped the piston and pad out with a M/C and the other one I did with a grease gun. I only got one thread started but it was enough.
 I scooped the grease out and put it into a spray can cap, now I have some pretty clean grease for whatever use. The original F pad (sometimes?) has an o ring around it that needs cleaned and I lubed it with a film of silicone high vacuum grease too.
 I bought pistons and seals from 4-1, they are K&L brand and decent enough quality.

The gl1000 rear master cylinder kit (caliper) is the same for the F1 but you’ll have something left over that the F1 doesn’t use but the gl does.  I haven’t forgotten what’s not used it’s just that my mind is like and old VHS tape it’s there,  it’s just hard to get it rewound to the right place when I want to..🤪

[bryanj]

If you can get Tourmax kits i am told by a trusted uk member they make for Honda

[Rnobx67]

Thanks I,ve order a new piston, do you know how to remove the circlips in the master cylinder, now the spring works couldn't see it...

[bryanj]

You need the special Honda circlip pliers plus a lot of wd40 and even more luck.
When i had a lot to do i use to use oxy acetylene down the hole to remove rust

[dave500]

there is a special place in hell,for the guy that designed where that #$%*ty circlip should reside!!

[jwurbel]

+1

[BenelliSEI]

+2! Here are the pliers you must have. Order two sets so when the tip finally snaps off the first set, you don’t get stopped in your tracks! Cheap sh*t, but they work.

This set is from Vintagecb750.com

[Kelly E]

+2! Here are the pliers you must have. Order two sets so when the tip finally snaps off the first set, you don’t get stopped in your tracks! Cheap sh*t, but they work.

This set is from Vintagecb750.com

Definitely always have a backup set of those I've on my 3rd set.

[RAFster122s]

It is a question of metallurgy and poor heat treat...
If they were made with good metal and given a good heat treat they would last, but then the company would have to charge a ton for them. Sometimes I don't mind paying for a good quality tool knowing I won't have to buy it again as long as I don't lose it or abuse it.

[scunny]

who loses tools?
I will now go into a corner and cry.

[BenelliSEI]

It is a question of metallurgy and poor heat treat...
If they were made with good metal and given a good heat treat they would last, but then the company would have to charge a ton for them. Sometimes I don't mind paying for a good quality tool knowing I won't have to buy it again as long as I don't lose it or abuse it.

Mostly the problem is those clips are often seriously stuck in place and the pin ends are extremely small…….

[Kelly E]

Now when the MC snap rings are really stuck I use a pick to try and to get each hole on the snap ring to move some before I get out the snap ring pliers.

[Jerry Rxman Griffin aka MuthaF'er]

Soak it with strong vinegar to help dissolve the rust

[Don R]

 Cleaning vinegar is stronger, as is week killer vinegar.
  I just thinned a set of snap ring pliers to fit in the master cylinder. My set had a pair that matched so I sacrificed them to make one more usable.
  Some of the F brakes have an o ring on the OD of the piston side pad. I assume it's to keep dirt out. I removed one of mine, the pad seemed to hang up because it was there. I also got a new aftermarket piston that hung up in the bore of two different calipers, I spent a few minutes polishing it with red Scotchbrite pad while talking to a neighbor. Now it slides in and falls out with no seal.

[Kelly E]

  I just thinned a set of snap ring pliers to fit in the master cylinder. My set had a pair that matched so I sacrificed them to make one more usable.

I thinned a set of long handle 90° needle nose pliers and ground tips into them to get out seized fork slider snap rings. They can be every bit as hard to get out as the MC snap rings. The next MC I take apart I'll get to try and see if my new Kowa snap ring pliers will fit down in there.