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Author Topic: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***  (Read 622 times)

Offline 77kztwinn

  • Posts: 7
Hi guys and gals I have a 77kz750 twin and im having issues with the rear brake rotor rubbing on the caliper bracket, not just a slight touch but making decent contact enough where the wheel will not free spin. I purchased the bike with this problem so i replaced all wheel bearings they are pressed in correctly, new seals, but problem still exists. I was almost thinking its bent but the bike would have to take a nasty fall not to mention the bracket is cast so i cant see it bending??? i have the spacers correct ive read the service manual 100 times and still cant figure it out, ive played with chain adjusters and the only way i can get it to not drag (as much) is to cock the wheel sideways by running out one adjuster further than the other. Could the bracket be twisted? Thanks for any help 

« Last Edit: Mar 01, 2018, 23:06:14 by 77kztwinn »

Offline teazer

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Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #1 on: Mar 01, 2018, 11:01:03 »
It's hard to tell from that picture but it looks as if it is bent to the left at the top.  Take it off and check it on a flat surface.

Does the caliper slide on its pins side to side and do both pads have enough meet left on them? And does the piston retract a little after you release the pedal?


Offline 77kztwinn

  • Posts: 7
Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #2 on: Mar 01, 2018, 11:13:20 »
Im going to take it off tonight after work and check it on a flat surface, I haven't installed the caliper yet, i have new pads in it and im just waiting for a new rear brake line so i dont know about the piston retracting.

Offline Streetfighterkz

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Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #3 on: Mar 01, 2018, 14:11:02 »
Check your wheel spacers. You could have the right two interchanged. Not sure how you would ever bend a bracket like that.

Later, Doug
'78 Kz1000
'76 Kz900 'Stripfighter (work in progress)
'83 Gpz750 (work in progress)
'89 V-Max
'89 Gsxr750 Trackfighter

Offline jpmobius

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Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #4 on: Mar 01, 2018, 15:29:08 »
Looks bent -- yes, hard to tell from the pic.  The bracket certainly can be bent.  Generally very UN-advisable to un-bend it, especially being a primary brake component.  Castings don't like to be deformed, and like even less to be forced to return to their original shape, so proceed at your own risk if you attempt to straighten it.
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline 77kztwinn

  • Posts: 7
Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #5 on: Mar 01, 2018, 16:30:31 »
Thanks for the replies!! I will post a picture of the bracket on a flat surface tonight once I get it removed.

Offline doc_rot

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Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #6 on: Mar 01, 2018, 17:36:08 »
get some photos of wheel spacers you are using as well.

Offline 77kztwinn

  • Posts: 7
Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #7 on: Mar 01, 2018, 17:46:29 »
Will do!

Offline crazypj

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Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #8 on: Mar 01, 2018, 20:40:43 »
Bracket is most probably bent, it's a very common problem when people 'cut corners' to 'save time'.
 I've had probably two dozen Suzuki caliper mounts bent like that. Haven't found a decent spec to try and 'straighten' them though so they end up as scrap aluminium. it may be possible to salvage it if you first anneal it in oven at 400f for about 30~40 min
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline 77kztwinn

  • Posts: 7
Re: 77 kz750 Rear rotor dragging on caliper bracket?
« Reply #9 on: Mar 01, 2018, 22:08:02 »
Okay well I figured it out.. When I did the wheel bearings, the kit for the rear came with the one larger bearing for the rear hub...well I did the ones in the wheel but never changed that one because that one had no play, seal seemed ok..and of all honesty I was rushing to put the bike back together stupid me. It came with the kit why not just change it..so I took the 10 minutes and changed it, cleaned it up, put everything back together and what do you know..we have a free spinning wheel, no contact to the rear bracket whatsoever.. I'm still wondering why but changing that bearing solved the problem.

Offline doc_rot

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #10 on: Mar 02, 2018, 00:04:11 »
Right on glad you figured it out. Do you have the internal bearing sleeve for  that carrier? I have seen that part not installed on many bikes, including a basket case Irecently  picked up.

Offline 77kztwinn

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #11 on: Mar 02, 2018, 00:09:45 »
Thanks man and yes luckily it was there!

Offline teazer

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #12 on: Mar 02, 2018, 00:46:43 »
I had one GS750 rear wheel where the spacer between hub and sprocket carrier was missing and the wheel bearings were probably 1 mile or less from completely collapsing. The cages were distorted and snapped and balls were far from round.  The PO dodged a bullet there.

That spacer MUST be in place between the sprocket carrier and wheel bearing.

Offline teazer

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #13 on: Mar 02, 2018, 00:48:01 »
Just had another thought.

I wonder if this time you swapped the left and right spacers over without realizing it....

Offline 77kztwinn

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #14 on: Mar 02, 2018, 09:52:12 »
Thats crazy how people can leave a spacer out like that, I did realize it goes in both ways but is slightly longer on one side, the book had no reference for which way it goes in but maybe that was the problem?

Offline crazypj

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Re: 77 kz750 Rear rotor dragging on caliper bracket? ***Fixed***
« Reply #15 on: Mar 02, 2018, 11:59:44 »
Right on glad you figured it out. Do you have the internal bearing sleeve for  that carrier? I have seen that part not installed on many bikes, including a basket case Irecently  picked up.

It's very very common to be missing on Kawasaki's, the sleeve fit is much 'looser' than most other manufacturers use so they fall out when carrier is removed (or stay on wheel hub then fall on floor when wheel is moved) It isn't a parallel spacer but has a tihnwall extension to fit into bearing reducing inner diameter
When I worked in Honda/Triumph dealer we kept a few in stock  as they were almost almost missing when bikes came in for tyre changes or wheel bearing replacement because bearing 'just broke up'
 One guy rode from Germany  to airbase in South Wales (about 700 miles) with rear wheel loose about 500 
« Last Edit: Mar 02, 2018, 12:02:35 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0