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Discussion Starter #1
My in-law has a 78 or 77 KZ1000. The rear brakes lock up on almost every ride. He's taken it to a shop to fix it at least twice and it still locks up on him. I'm thinking it could be the rear wheel out of alignment but if that is not the case what else could be causing this? I'm pretty sure he had all new brakes installed the second time at the shop and it still does it. It's why I think it might be in the wheel.
 

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Rear disc brakes or drum? If disc brakes, replace the brake fluid as it may have water contamination causing the piston in the caliper to stick.

If that won't help, then a re build is in order. Contact Z1 Enterprises, Inc. - Specializing in Vintage Japanese Motorcycle Parts
for a kit.

If the rear brakes are drum type, remove the rear wheel, and inspect the brake shoes, as there have been problem with the adhesive failing causing the shoes to bind up the drum.

While you're in there, clean the shoe pivots and re-lube them with high temperature grease(not a whole lot, just enough for lubrication).
 

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Rear disc brakes or drum? If disc brakes, replace the brake fluid as it may have water contamination causing the piston in the caliper to stick.

If that won't help, then a re build is in order. Contact Z1 Enterprises, Inc. - Specializing in Vintage Japanese Motorcycle Parts
for a kit.

If the rear brakes are drum type, remove the rear wheel, and inspect the brake shoes, as there have been problem with the adhesive failing causing the shoes to bind up the drum.

While you're in there, clean the shoe pivots and re-lube them with high temperature grease(not a whole lot, just enough for lubrication).
+1! :wink:
 

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Twice for the same problem. Might be time to change mechanics.

Sounds like a caliper is sticking or possibly the master cylinder is not returning far enough to allow fluid flow between the line and the reservoir if it's disc. Caliper rebuild & clean fresh fluid will take care of the caliper. The rear master cylinder may either have the hole for the reservoir fluid passage clogged, but more likely is that the master cylinder piston is not returning far enough to open the passage. That will trap the fluid in the line and not allow the pads to retract off the disc when they heat up, locking the wheel. Both problems would require a master cylinder clean and rebuild. I just saw that problem in another post possibly on another forum.

On the back the only two things I can think of are lining coming off or shoe breaking and locking; or shoes worn so bad the activation cam goes to center and sticks. I had the latter happen to me AND the shoe broke at the same time on my first off road bike. Cleaned pivots, good shoes and some light greasing of moving parts should fix that.
 

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Discussion Starter #5
Thanks guys. I'm going to try and look at it for him and see if I can tell what the previous mechanic did so far. I know for sure they replaced the brake lines but not sure what else they did.
 

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Many times what happens as well is residual mositure that's within the brake fluid causes the piston bore in the wheel cylinder to form corrosion. This prohibits the piston from retracting the .030" that needed to relieve pressure on the disc when you release the brake pedal. blow out the piston, sand the inner bore with 220 emery and some oil, pop in a new seal, and you should be good to go !
 

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Discussion Starter #7
Many times what happens as well is residual mositure that's within the brake fluid causes the piston bore in the wheel cylinder to form corrosion. This prohibits the piston from retracting the .030" that needed to relieve pressure on the disc when you release the brake pedal. blow out the piston, sand the inner bore with 220 emery and some oil, pop in a new seal, and you should be good to go !
I'll for sure take a look at that as well. Thanks!
 
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