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Front brake lockup 20 Apr 2019 10:11 #802470

  • Oldjeep
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No eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configurationWas taking the bike for a spin this morning and I kept having trouble pulling away from stop signs. Then I went around a slow corner and the tire seemed to lock when I hit some sand. Got it home and could barely push it around, turned out that both front rotors were pretty hot and the brakes are locked up.

My inclination is new MC and lines since they are original. The brake lever makes some weird squeaking sounds when I press it, so I'm thinking that the O-rings are doing something odd in the MC.

Any reason to not just start replacing parts? Looks like a new MC/lever is $35 and some stainless lines are $100

Looking at these, unless someone has a better suggestion. (81 KZ750 LTD)

Chuck
81 KZ750 LTD
03 FZ1
www.oldjeep.com

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Front brake lockup 20 Apr 2019 10:18 #802471

  • gordone
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I have bouth the same front master cylinder for 2-3 years ago, no problem so fare.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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Front brake lockup 20 Apr 2019 10:25 #802472

  • ajsfirehawk
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Since both front rotors are hot I suspect you are right, the MC is the likely culprit. Have you rebuilt the calipers?
79 KZ650 SR
80 KZ1000 Z1 Classic
83 KZ1100 LTD
Z900RS
23 Mach 1

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Front brake lockup 20 Apr 2019 10:27 #802473

  • Oldjeep
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No, the only brake work I did when i got it was new pads since everything seemed to be working.
Chuck
81 KZ750 LTD
03 FZ1
www.oldjeep.com

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Last edit: by Oldjeep.

Front brake lockup 20 Apr 2019 11:01 #802474

  • Nessism
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You are on the right track. That master will work and replacing the lines is critical since the old ones are sure to be full of crud and the rubber deteriorated. I'd add a teardown of the calipers to the list of things to do since they are likely full of crud too. Changing the seals is a good idea and if the piston is pitted that should be changed too. OEM seals are the way to go. K&L brand brake system parts suck. I've had nothing but bad experiences with them.

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Front brake lockup 21 Apr 2019 05:17 #802517

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No eBay APP ID and/or Cert ID defined in Kunena configurationOk, ordered up some caliper kits too. Hopefully the pistons are ok. I will likely strip everything tonight. Won't have parts until Friday.
Chuck
81 KZ750 LTD
03 FZ1
www.oldjeep.com

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Front brake lockup 21 Apr 2019 07:35 #802530

  • Oldjeep
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As predicated, all full of gunk and pitted pistons
Chuck
81 KZ750 LTD
03 FZ1
www.oldjeep.com
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Front brake lockup 21 Apr 2019 07:45 #802533

  • SWest
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That looks like a aftermarket MC anyway.
Steve

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