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Discussion Starter · #1 ·
I got a new Master Cylindar the other day, and I installed it. When I bought the bike, the old one was beyond repair, so I never messed with the front brakes. I took the caliper off and cleaned it up. I pushed the piston in, it was tough, but it moved. It was similar to a car's piston. I put new brake pads on, re-installed the caliper, then bled the brakes. Now, the front wheel will not turn. The caliper does not free up at all when the brake lever is not being depressed. What would be the cause of this?
 

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Crack open the bleeder screw to release the pressure. If it is still locked up, the caliper is not releasing properly.



If removing the pressure causes it to unlock, it could be a blocked return hole inside the master cylinder. A blocked line is also possible.
 

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Discussion Starter · #4 ·
Crack open the bleeder screw to release the pressure. If it is still locked up, the caliper is not releasing properly.



If removing the pressure causes it to unlock, it could be a blocked return hole inside the master cylinder. A blocked line is also possible.




Thanks. I'll try this tonight.
 

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Discussion Starter · #5 ·
I did this test and it is the caliper. Since this bike sat uncovered for 20+ years, I suppose it makes sense. I was just hoping one item on the bike would not need rebuilt. So I disassembled the caliper last night, all except for the piston that would not come out. I cleaned it in my ultrasonic cleaner a few cycles. The piston still would not budge. I then soaked it in PB Blaster for an hour, and still nothing. I then switched to CLR for a few hours, and nothing. I went back to PB Blaster and let it soak over night. I will try it when I get home from work. I did not have any diesel on hand, and I was too lazy to go get any last night. If it does not come out this evening, I will go get some diesel.



On the bright side, I did get my carbs reassembled last night while I was waiting on the caliper to soak. I had to buy another set of carbs because a piece was broken on my left side body. Looking at the other set of carbs and seeing their condition, it finally dawned on me how bad of shape my bike was in when I bought it. The "new" set of carbs disassembled in 30 minutes. When I first took apart my old carbs, it took 3 days and lots of soaking, cleaning, and cursing.



So, once the caliper is working, I move to the motor, then to the road.
 

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Put a rag in the caliper where the brake pads go, then use compressed air at the brake line connection to push out the piston. Keep your fingers out of the way, that is what the rag is for--- to absorb the impact.
 

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Discussion Starter · #8 ·
Put a rag in the caliper where the brake pads go, then use compressed air at the brake line connection to push out the piston. Keep your fingers out of the way, that is what the rag is for--- to absorb the impact.




Yeah... I tried that. It did not budge. I am thinking if I soak it a bit more, then eventually the air will push it out. I have a pretty big air compressor, so if mine won't push it out, I think more soaking is in order.
 

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BTDT many times, why Honda didn't use a booted piston I don't know.



If compressed air didn't work, then your best option is a grease gun. The grease gun fitting will snap right onto the bleeder screw, you need to find a normal bolt that fits in the hole where the banjo bolt is.



Then pump away, after a couple pumps you'll see a piston start to move. Put a C-clamp over (in) that piston, then pump again, when the other side is about even, back out the C-clamp and repeat. Only downside is that you'll have to clean up the grease, but since everything's clean, you're not even out the grease, you can re-use it.



The mistake was pushing the pistons back in, when you come across a stuck caliper that's been that way for years, remove it from the fork, remove the pins and pads, place one pad in facing the pistons and pump the master to see if you can get the pistons out. If that doesn't work, compressed air will pop them out (watch those fingers.)



BTW-it HAS to be a pump style full size grease gun (you can pick them up at most parts stores for about $10 if you don't already have one) air powered ones will not work. If the writing on the cylinder is true, you can get 10,000 PSI at the tip. If the pistons don't pop out with that, somebody welded them in there!
 

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Discussion Starter · #10 ·
BTDT many times, why Honda didn't use a booted piston I don't know.



If compressed air didn't work, then your best option is a grease gun. The grease gun fitting will snap right onto the bleeder screw, you need to find a normal bolt that fits in the hole where the banjo bolt is.



Then pump away, after a couple pumps you'll see a piston start to move. Put a C-clamp over (in) that piston, then pump again, when the other side is about even, back out the C-clamp and repeat. Only downside is that you'll have to clean up the grease, but since everything's clean, you're not even out the grease, you can re-use it.



The mistake was pushing the pistons back in, when you come across a stuck caliper that's been that way for years, remove it from the fork, remove the pins and pads, place one pad in facing the pistons and pump the master to see if you can get the pistons out. If that doesn't work, compressed air will pop them out (watch those fingers.)



BTW-it HAS to be a pump style full size grease gun (you can pick them up at most parts stores for about $10 if you don't already have one) air powered ones will not work. If the writing on the cylinder is true, you can get 10,000 PSI at the tip. If the pistons don't pop out with that, somebody welded them in there!




Thanks for the ideas everyone. I finally got it out. The winner was... THE GREASE GUN!



I pumped it a few times with no resistance, then all the sudden in got a bit tough, but with each pump, the piston came out about 1/8 inch. There was no violent piston explosions as I expected. It was smooth and simple. Parts are in the cleaner right now getting de-greased. I am hoping to have functioning brakes tonight, as long as the parts look ok once they are clean.
 

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ok - you all seem to know what you are doing . . . and have a bit of experience.
For a newbie is there a redo the brake system for dummies with pictures of what things look like ?

My brakes won't release . . . I just put on a new Master Cylinder and new stainless brake lines for 1982 Honda GL500I dual brakes - -bleed them (first time ever) and they worked - yeah for me! Now they won't release.

So from reading here I guess they need a rebuild or buy new ones. Never done this before - looking for an educational experience.

Do I disconnect the brake lines from the brake/calipers before tearing them apart - assume yes.
 

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The seal in the caliper probably needs to be replaced. Take the calipers off, you might be able to pump the breaks to get the pistons out and replace the rubber seals in there.
 

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Did you replace the brake pads as well? If you pump the pistons out use a block of wood or metal to keep pistons even. If one pops out first you have no more pressure left in system. go slow and even on each side
 

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first open the bleeder on any one of the brakes

does fluid come out and the brakes release?

if you the problem is dirt/debris plugging the master cylinder return hole

if the brakes dont release when you open the bleeder its the calipers
 

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will check tonight and get back to all . . .

ps. this is all new to me . . .but here to learn . . .
Good attitude, we are here to help you learn. If you don't have it yet, get a free copy of the Factroy Service Manual from the WIKI below, making sure to also get the appropriate addendum.
Also add the bike details to your signature line in your profile. Then we always know how best to help you.
 

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ok - loosened the brake line and fluid came out - no bubbles . . . brakes didn't release . . . as I thought it must be the brake/calipers.
When I bought the bike early October it had no front brake lines; so I am guessing they got gummed up and dirty.

I am also adding a garage heater so I can work on this over the wonderful Minnesota winter :-O, I put in the gas line over the weekend and now need to get the heater and install it after the city inspector approves it.

I will next tear apart the calipers and learn more . . . maybe this weekend . . .

Thank You for all the help here . . .
 
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so I've been busy with the heater system and Thanksgiving - - but tonight I tapped the calipers with a rubber hammer and the brakes released . . . tried the brake again and they locked up, tapped with rubber hammer released . . . yep dirty calipers . . . will need to get them torn apart this weekend . . . and yes new pads will go on as well since that makes sense . . .

Mike B
 
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