Author Topic: 1976 750f rear brake question  (Read 1557 times)

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Offline fatkid

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1976 750f rear brake question
« on: July 03, 2011, 05:02:38 PM »
hey guy started looking over the brakes both front and rear master cylinders are stuck . i got the rear one off and took the retainer clip off which allowed the what i am going to call the plunger out but the rest is stuck up in it . any tricks to getting it out so I may rebuild.

Offline BeSeeingYou

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Re: 1976 750f rear brake question
« Reply #1 on: July 03, 2011, 10:34:59 PM »
I had the same problem with my rear MC.  What you got out is the pushrod and the piston is stuck up inside.  Probably looks like this first pic.  I put some penetrating fluid and let it sit for a while. Nothing.  Heated the whole thing with a heat gun. Nothing.  Took a screwdriver and pushed down hard on the piston and it moved in about 1/4 inch.  Nothing.  Decided to leave it till morning and when I set it down the piston popped out. :D

I think I would try the penetrating oil and maybe try shooting in compressed air through the outlet port.  Have the cap on the reservoir.  If that doesn't work try my technique ( I think the additional compression on the spring did it).  As a last resort I was going to drill a hole into the piston for a screw and pull it out with that.

As for the front make sure you get the wire clip that holds the boot in place out as it will sit on top of the c clip.  Once that is out find a way to hold down the piston as this will take pressure off the c clip and make removal easier.  You need a deep reach c clip pliers and you won't find them at hardware or auto stores.  mikesxs.com has them for around $10.00 or do a search and see how others have done it with modified tools.  I filed down the tips of a long needle nose pliers.  If you are in no hurry the $10 spent and a few days wait are less aggravating than the alternatives.  You can see the wire boot clip in the second photo of the front MC internals.  Third pic is the rear MC internals.
« Last Edit: July 03, 2011, 10:45:15 PM by srust58 »

Offline fatkid

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Re: 1976 750f rear brake question
« Reply #2 on: July 04, 2011, 05:43:48 AM »
hey thanks again srust58 as always you are a book of knowledge. i got the front apart and back together it doesn't feel like its building much pressure so may need a rebuild. now the rear is a nother story . i have it soaking up some penetrating lube now . tried the air and the tapping but no go so we will let it set a while . if I cant get it i may have to ship it to you and have you tap it on that magic bench of yours. hey thanks again. oh also tried taking the front brake and hooking it up to the out put side and pump it back but couldn't seal up the line . cant beat hydraulic power.

Offline fatkid

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Re: 1976 750f rear brake question
« Reply #3 on: July 07, 2011, 05:42:40 PM »
well i let it soak for 3 or 4 days tried air agian nothing so i took a grease fitting and tap and died it to 10mm by 1.25 mm screwed it in and about 20 pumps later i was holding everthing i needed. Had to fill ya in just incase u ever lost that magic table or anyone else needs to get one apart. any ideas or comments about a rebuild kit

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: 1976 750f rear brake question
« Reply #4 on: July 07, 2011, 07:53:08 PM »
Honda.

Grease guns seem to work the best and are not potentially lethal like compressed air at 120psi. How about doing a little more detailed write up with pictures for us other F guys? I don't believe I've seen it done this way on the rear.
« Last Edit: July 07, 2011, 07:56:54 PM by Jerry Rxman Griffin »
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline BeSeeingYou

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Re: 1976 750f rear brake question
« Reply #5 on: July 07, 2011, 08:08:44 PM »
Great to hear though I did clear a spot on the magic bench. ;)  If you remove the bolt below the reservoir it will give you access to the send and return holes so you can clean them out.  The return is very small and impossible to see looking up into the bore.  The OEM rebuild kits goes for about $40 and includes the boot and pushrod.  The seals for the caliper are sold individually so you need the two piston seals and the small o ring joint seal. The dust boots are available too but I was able to reuse my old ones.  The rear caliper is a twin piston design and also made up of two parts.  I used my rebuilt front MC to pump out the pistons.  Use a small C clamp to hold the outboard one in and slow and easy pump out the inboard piston.  Clean out the seal groove and replace the piston, new seal and do a quick bleed.  Clamp that one down and pump out the other.  Once you get them both done you can split the caliper and replace the small O ring joint seal.
« Last Edit: July 07, 2011, 08:13:47 PM by srust58 »

Offline BeSeeingYou

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Re: 1976 750f rear brake question
« Reply #6 on: July 07, 2011, 08:12:06 PM »
Honda.

Grease guns seem to work the best and are not potentially lethal like compressed air at 120psi. How about doing a little more detailed write up with pictures for us other F guys? I don't believe I've seen it done this way on the rear.

I would second that.  I was not sure this method would work on the rear MC.  But then....I had a magic bench. ;D
« Last Edit: July 07, 2011, 08:15:29 PM by srust58 »

Offline KRONUS0100

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Re: 1976 750f rear brake question
« Reply #7 on: July 07, 2011, 09:47:47 PM »
or you all could do what i did if stock parts dont matter.  I purchased a rear master off a 2006 SUZUKI GSXR 600...........and fabbed a little mounting bracket for it.  trim a lil bit off the linkage, and its good to go.
I got pics of it on here somewhere
MATT
current bikes:  1976 CB750F, 1981 GS1100E
bikes owned:1981 GL1100I, 1990 GS500E, 1981 GS850, 1977 and 1979 GS750, 1974 CB750, 1975 CB750, and a 1982 GS750E

Offline fatkid

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Re: 1976 750f rear brake question
« Reply #8 on: July 08, 2011, 04:51:49 AM »
hey guys getting ready to leave on vacation so will post pics later next weak. kinda hope vacation goes quick i want to get back and get on this thing.
KRONUS0100 good idea i am sure that would work great. I just cant do it to this old girl she has only 1646 original miles on here . but thanks for the idea