1984 GPZ550 rear brake stuck

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18 Jun 2020 11:58 #828392 by dpivas7
1984 GPZ550 rear brake stuck was created by dpivas7
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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  • Scirocco
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18 Jun 2020 12:36 #828398 by Scirocco
Replied by Scirocco on topic 1984 GPZ550 rear brake stuck
Looks more like an rear MC and caliper clean and rebuild Job.
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18 Jun 2020 13:27 #828402 by TexasKZ
Replied by TexasKZ on topic 1984 GPZ550 rear brake stuck
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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18 Jun 2020 13:41 #828404 by dpivas7
Replied by dpivas7 on topic 1984 GPZ550 rear brake stuck
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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18 Jun 2020 14:09 - 18 Jun 2020 14:11 #828406 by TexasKZ
Replied by TexasKZ on topic 1984 GPZ550 rear brake stuck
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
Last edit: 18 Jun 2020 14:11 by TexasKZ.
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18 Jun 2020 14:43 #828411 by dpivas7
Replied by dpivas7 on topic 1984 GPZ550 rear brake stuck
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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18 Jun 2020 15:48 #828416 by ThatGPzGuy
Replied by ThatGPzGuy on topic 1984 GPZ550 rear brake stuck
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
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2001 Yamaha YZ426
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18 Jun 2020 16:01 #828417 by Nessism
Replied by Nessism on topic 1984 GPZ550 rear brake stuck
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.
Ed
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0

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1981 KZ750E2
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19 Jun 2020 12:52 #828476 by ned37
Replied by ned37 on topic 1984 GPZ550 rear brake stuck
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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28 Jun 2020 12:11 #829216 by dpivas7
Replied by dpivas7 on topic 1984 GPZ550 rear brake stuck
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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28 Jun 2020 14:32 #829226 by dpivas7
Replied by dpivas7 on topic 1984 GPZ550 rear brake stuck

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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28 Jun 2020 15:18 #829242 by Mikaw
Replied by Mikaw on topic 1984 GPZ550 rear brake stuck
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
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