1978 KZ1000 A2A rear brake question

I was trying to remember where I read about the little orifice so I poked around a little; here are some links to discussions about sticking brakes:

kzrider.com/forum/24-wanted/463485-1977-...nder-assembly#463487

kzrider.com/forum/5-chassis/466278-brakes#466294

kzrider.com/forum/5-chassis/496315-front...not-releasing#496319

kzrider.com/forum/5-chassis/515527-front-brakes-stick#515620

Ed

Really helpful!! I have dinked with the push rod thinking it might need more free play, but never got very aggressive about adjusting it. Tomorrow may be a fine day. Thanks for the pic also.

Thanks for the other brake discussions Ed and for the parts link MFolks. I've not tried partsnmore. Nice to have some good people with good advice. The new pads may also be productive if none of the other fixes it. Thanks to all.

I've read/heard about some after market brake pads being too thick, so I'd check what you've got.

Well, several hours later (about 5-6 R&R and testing) and I've still got a rear brake problem on the 1978 KZ1000. I have R&R and thoroughly cleaned the calipers, pistons, banjos and line, master cylinder, and flushed the fluid. Thought I'd be cruzin' in style but the problem is still there only slightly better. So, back to the shop and let the pads cool down till the rear wheel will turn as it should. I started checking the rotor to see if maybe it was warped. It is not perfect. It has a slight distortion, but I don't think it is enough to cause the problem. Even when you do NOT use the rear brake, it gets hot and applies pressure to the pads. You can easily feel the drag when "coasting" to a stop.

So, I looked up the IPB for the rear wheel assembly and it looks like all washers and parts are there and in order, but it appears the rear caliper assembly is NOT parallel with the rotor. The top seems to be farther away than the bottom (where the axle goes through). I'm thinking about adding washers until the caliper is aligned with the rotor. By the way, the inner brake pad is worn more than the outer, but still in "range" for wear.

Any thoughts??

wurf

There should be pins(bolts) the caliper slides on. If your have corrosion,or the caliper is binding somehow, this could make braking action compromised. I believe they need a high temperature silicone grease for lubrication.

You should have this brake;


So Both Pistons must move freely, as they are the self adjusting mechanism.
You should be able to easily pry back on either side and have the piston enter back in to its bore. If not try cracking the bleeder, if it then moves look back to the master cylinder Vent Hole.

Motor Head,

You are right on with the IPB. If the bleed valve is opened, it will release pressure and the pistons can be compressed into the caliper and fluid will squirt out of the bleed. However, the deal is that even if I DO NOT touch the rear brake pedal during a two - three mile ride the rear pads contact the rotor, get hot, and cause enough friction to slow the bike in neutral. I do not believe it is a return orifice blocked problem. I THOROUGHLY cleaned and tested the return fluid path to the master cylinder during the R&R of both the master cylinder and caliper assembly.

The outer piston has pitting around the end next to the pad. It DOES NOT leak fluid; however, I think the piston sticking could be part of the problem. The thing that bother me the most is the "misalignment" of the calipers and the rotor. I may replace the outer piston and seal, or both for that matter, but it looks like the calipers are leaning out at the top compared to the rotor.

wurf

You cleaned but didn't install new seals in the calipers, or master? Alignment might be an issue, but the seals can be also. As they can swell slightly if contaminated, any corrosion/ pitting on the piston can cause it to hang. Pitting in the bore, can be honed a bit as it will only hold fluid. Pistons must fit easily without any seal. New seals should be lubed with Sil-glide, or new DOT4.

Hey to Avoyshift5, Motor Head, MFolks, Patton, 650ed, ramtough_63, and wireman,

Sorry for just bailing on the 1978 KZ1000 rear brake trouble. I ended up replacing both rear piston seals and the inside-pitted piston. Then adjusted the brake pedal so there is more clearance before it contacts the master plunger. I think the caliper misalignment was an optical illusion on my part. At this time the problem seems to be mostly fixed. I do have a slightly warped rotor, but the rear brakes work fine and have only gotten hot once.

The only thing hot these days is the bike and the weather - we've had temps over 100 and up to 107 for about 2 weeks now.

Thanks again for all the good advice.

wurf