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1984 GPZ550 rear brake stuck 18 Jun 2020 11:58 #828392

  • dpivas7
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The rear brake on this 1984 GPz550 I am working on is stuck. when you press on the brake lever, the lever doesn't return, even though the spring is still attached to the mechanism. The reservoir is filled with fluid to the correct level.

Does it need a simple brake bleed or is there something wrong with the caliper?
Current: '19 Harley Roadster, '72 XLCH, '84 GPz 550
Past: '84 GPz 550, '82 KZ750 LTD, '71 XLCH

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1984 GPZ550 rear brake stuck 18 Jun 2020 12:36 #828398

  • Scirocco
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Looks more like an rear MC and caliper clean and rebuild Job.

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1984 GPZ550 rear brake stuck 18 Jun 2020 13:27 #828402

  • TexasKZ
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Could be the brake lever pivot. It is one of those oft neglected maintenance items. Water and dirt can build up, causing rust on the pivot shaft.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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1984 GPZ550 rear brake stuck 18 Jun 2020 13:41 #828404

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The brake stays locked, even if I pull the lever up
Current: '19 Harley Roadster, '72 XLCH, '84 GPz 550
Past: '84 GPz 550, '82 KZ750 LTD, '71 XLCH

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1984 GPZ550 rear brake stuck 18 Jun 2020 14:09 #828406

  • TexasKZ
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Then it seems a full hydraulic rebuild is in order, though I would still pull the lever off to clean and grease the pivot. Be sure to carefully clean the seal groves in the caliper.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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Last edit: by TexasKZ.

1984 GPZ550 rear brake stuck 18 Jun 2020 14:43 #828411

  • dpivas7
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Ahh okay! Would it be sufficient to buy a caliper rebuild kit?
Current: '19 Harley Roadster, '72 XLCH, '84 GPz 550
Past: '84 GPz 550, '82 KZ750 LTD, '71 XLCH

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1984 GPZ550 rear brake stuck 18 Jun 2020 15:48 #828416

  • ThatGPzGuy
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This just happened to me on my XS650. You'll need to pull the MC and rebuild it. I would suggest honing as well since the piston is probably seized in the bore.. Try that first and then, if needed, rebuild the caliper.
Jim
North GA
2016 Yamaha FJR1300ES
1982 GPz750 R1
1974 Kawasaki H1
1976 Kawasaki KZ400
1979 Yamaha XS650 cafe'
2001 KZ1000P
2001 Yamaha YZ426
1981 Honda XR200 stroked in an '89 CR125 chassis
1965 Mustang
1967 Triumph GT6
1976 Bronco
"If you didn't build it, it's not really yours"

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1984 GPZ550 rear brake stuck 18 Jun 2020 16:01 #828417

  • Nessism
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Motorcycle master cylinders should not be honed. Pull it apart and inspect for pitting in the aluminum. If it's okay install an OEM piston kit and replace the brake line. Same goes for the caliper, only instead of worrying about the bore look at the pistons.

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1984 GPZ550 rear brake stuck 19 Jun 2020 12:52 #828476

  • ned37
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sounds like the small return bleed hole in the mc is plugged, keeping the pressurized fluid from returning from the caliper
'83 GPZ1100, '97 Triumph Trophy 1200, '08 Husky TE610
Verde Valley, AZ

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1984 GPZ550 rear brake stuck 28 Jun 2020 12:11 #829216

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I don't see a bleed hole anywhere.
Current: '19 Harley Roadster, '72 XLCH, '84 GPz 550
Past: '84 GPz 550, '82 KZ750 LTD, '71 XLCH

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1984 GPZ550 rear brake stuck 28 Jun 2020 14:32 #829226

  • dpivas7
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Nessism wrote: Motorcycle master cylinders should not be honed. Pull it apart and inspect for pitting in the aluminum. If it's okay install an OEM piston kit and replace the brake line. Same goes for the caliper, only instead of worrying about the bore look at the pistons.


I can't find any rebuild kits for a 1984 GPz550. Would a 1982-1983 rebuild kit work? The manual says "The rear master cylinder on ZX550-A1 and A2 models has changed slightly from other models" so I don't know if a 1983 would work.

Also can't find any complete rear master cylinders for less than $300
Current: '19 Harley Roadster, '72 XLCH, '84 GPz 550
Past: '84 GPz 550, '82 KZ750 LTD, '71 XLCH

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1984 GPZ550 rear brake stuck 28 Jun 2020 15:18 #829242

  • Mikaw
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This is the tiny hole that allows pressure to be released and allows the caliper to back off a smidge and not drag

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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