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Author Topic: 1976 cb750 super sport rear brake  (Read 1476 times)

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Offline Sportyspice

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1976 cb750 super sport rear brake
« on: July 10, 2017, 09:02:28 PM »
I've rebuilt the caliper and cleaned the master cylinder on the rear disc brake.  The master cylinder was pretty coroded but I cleaned it fairly well with with out taking it apart and the rear brake still starts to stick after about 5 good stops.  The pads start smoking and it's kind of a mess. Any recommendations would be great. Looks like I can buy an OEM rebuild for the master but I feel like throwing more money in parts is the route I always take and that's not always the best bet.  I'd love any thoughts you may have.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: 1976 cb750 super sport rear brake
« Reply #1 on: July 10, 2017, 10:23:53 PM »
Where are you going to find a OEM kit for the master?! Good luck with that. Another option is use the kit for the 75 - 79 GL. The rod is only slightly longer but works fine. The GL master is the same except how the brake tube exits/attaches and it does not have the built in stop at the connection.

The caliper kit can be had with BOTH new pistons from SiriusConInc.com for a decent price. 
« Last Edit: July 10, 2017, 10:27:17 PM by Jerry Rxman Griffin aka MuthaF'er »
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Offline TwoTired

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Re: 1976 cb750 super sport rear brake
« Reply #2 on: July 10, 2017, 10:34:46 PM »
Sounds like the brake pressure isn't getting relieved when the brake pedal is released.

A. There is a very tiny bleed hole that relieves pressure when the piston is retracted.  make sure that tiny hole is clear.
B. Make sure the piston can retract fully when the brake pedal is released.

C. Lastly, the brake line hose (rubber) can deteriorate internally and act as a check valve.  To check, loosen the banjo bolt when the caliper is dragging.  If brake fluid shoots out, replace the brake line.  Test is only good after A & B have been verified.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
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Offline madmtnmotors

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Re: 1976 cb750 super sport rear brake
« Reply #3 on: July 11, 2017, 04:12:40 AM »
Quote from: Sportyspice on July 10, 2017, 09:02:28 PM
The master cylinder was pretty coroded but I cleaned it fairly well with with out taking it apart.

No, you did not. The master cylinder cannot be properly cleaned without taking it apart. While you've got it apart you might as well repack it with new seals. We're talking about brakes here, not a burned out turn signal bulb.

TwoTired offers sage advice as well.  8)
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Offline Sportyspice

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Re: 1976 cb750 super sport rear brake
« Reply #4 on: July 11, 2017, 05:37:42 AM »
 
Quote from: TwoTired on July 10, 2017, 10:34:46 PM
Sounds like the brake pressure isn't getting relieved when the brake pedal is released.

A. There is a very tiny bleed hole that relieves pressure when the piston is retracted.  make sure that tiny hole is clear.
B. Make sure the piston can retract fully when the brake pedal is released.

C. Lastly, the brake line hose (rubber) can deteriorate internally and act as a check valve.  To check, loosen the banjo bolt when the caliper is dragging.  If brake fluid shoots out, replace the brake line.  Test is only good after A & B have been verified.

Is the small hole your talking about one of the two holes behind the piston in the caliper?  If so I blew compressed air through that when I had the caliper apart and all passages were clear.  As far as the piston retracting it will retract for a few stops then after about 5 stops its starts to fail to retract.  Brake lines are my next purchase, just was referred to a place through this form for braided steele lines. Thanks for the advice.
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Offline TwoTired

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Re: 1976 cb750 super sport rear brake
« Reply #5 on: July 11, 2017, 12:31:30 PM »
Quote from: Sportyspice on July 11, 2017, 05:37:42 AM
Quote from: TwoTired on July 10, 2017, 10:34:46 PM
Sounds like the brake pressure isn't getting relieved when the brake pedal is released.

A. There is a very tiny bleed hole that relieves pressure when the piston is retracted.  make sure that tiny hole is clear.
B. Make sure the piston can retract fully when the brake pedal is released.

C. Lastly, the brake line hose (rubber) can deteriorate internally and act as a check valve.  To check, loosen the banjo bolt when the caliper is dragging.  If brake fluid shoots out, replace the brake line.  Test is only good after A & B have been verified.

Is the small hole your talking about one of the two holes behind the piston in the caliper?  If so I blew compressed air through that when I had the caliper apart and all passages were clear.  As far as the piston retracting it will retract for a few stops then after about 5 stops its starts to fail to retract.  Brake lines are my next purchase, just was referred to a place through this form for braided steele lines. Thanks for the advice.

No.  The small relief hole is in the master cylinder.  And the master has a piston that must fully retract past that relief hole.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Sportyspice

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Re: 1976 cb750 super sport rear brake
« Reply #6 on: July 13, 2017, 10:36:28 AM »
Ahh perfect thank you.  The master was sticking a bit so that very well could be it. I ordered the OEM master rebuild kit for the same year gold wing and I'm getting stainless lines made so I hope to be stopping well by late next week.  I'm going with Speigler for the brake lines.  Anyone used them in the past and how was the experience?
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