1984 GPZ550 rear brake stuck

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1984 GPZ550 rear brake stuck

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

18 Jun 2020 12:36
#828398
Looks more like an rear MC and caliper clean and rebuild Job.
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  • TexasKZ
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Re: 1984 GPZ550 rear brake stuck

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

18 Jun 2020 13:41
#828404
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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Re: 1984 GPZ550 rear brake stuck

18 Jun 2020 14:09 - 18 Jun 2020 14:11
#828406
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

www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24
Last edit: 18 Jun 2020 14:11 by TexasKZ.
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Re: 1984 GPZ550 rear brake stuck

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

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

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

19 Jun 2020 12:52
#828476
sounds like the small return bleed hole in the mc is plugged, keeping the pressurized fluid from returning from the caliper
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Re: 1984 GPZ550 rear brake stuck

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

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

28 Jun 2020 15:18
#829242
This is the tiny hole that allows pressure to be released and allows the caliper to back off a smidge and not drag

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