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Front brakes seizing up after a few applications?!?

  • Thread starter Thread starter KnuckleBuster
  • Start date Start date
K

KnuckleBuster

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On a 1980 GS750 - The calipers seem to work okay, but if you squeeze the brake about 3 or 4 times, the brakes tighten up and don't want to release. If you crack the bleeders the pressure releases and the caliper frees up. This is a real problem while riding (not that I've been riding too far like this). The fluid level is right in the master cylinder.

What could be causing this problem?

The bike had been sitting for several years. I flushed the brakes with new fluid and bled them. Like I said, the calipers seemed to work fine....

Thanks,
Jay
 
Pull the Master cylinder off. I am willing to bet that the return hole in the MC is pluged. Get that fixed and then you will be good again.

Also with the bike having been sitting for years I would get new lines. Braided Stainless Steel lines are what you want, if the wallet says no to that then you need new rubber lines.

Check that little hole first!
 
I'll have to check that hole - that makes perfect sense. I haven't had to fiddle with a master cylinder on any of my bikes yet, so I wasn't sure what to look for, but that sounds like it.

I've considered braided steel lines from Paragon Performance for a while now (for all my bikes) I just haven't bitten the bullet and ordered them yet.

Thanks for the help!

P.S. Where is the little hole located? How do I clean it?
 
KnuckleBuster said:
On a 1980 GS750 - The calipers seem to work okay, but if you squeeze the brake about 3 or 4 times, the brakes tighten up and don't want to release. If you crack the bleeders the pressure releases and the caliper frees up. This is a real problem while riding (not that I've been riding too far like this). The fluid level is right in the master cylinder.

What could be causing this problem?

The bike had been sitting for several years. I flushed the brakes with new fluid and bled them. Like I said, the calipers seemed to work fine....

Thanks,
Jay
Click to expand...


Moisture has gotten into your brake system. Moisture corrodes the aluminum, and causes the piston to stick. You need to dissasemble and clean the piston bore. If you have severe corrosion, you will need to replace the caliper.
 
I agree with Road Clam. I had a lot of problems with my calipers at first. I took them apart to find that the pistons were corroaded. Ofter disassembley cleaning and the replacement of my pistons the brakes have never given me a problem.

The Beast
 
It just occured to me that when I was bleeding the master cylinder, The lever was very slow to return to its at-rest position. I had no problem squeezing the lever, but it took a while for it to return (we're talking seconds). That points towards the return hole, doesn't it?
 
KnuckleBuster said:
It just occured to me that when I was bleeding the master cylinder, The lever was very slow to return to its at-rest position. I had no problem squeezing the lever, but it took a while for it to return (we're talking seconds). That points towards the return hole, doesn't it?
Click to expand...

No, that points toward corrosion in the MC bore. You probably have all kinds of icky schmutz in there.

CRC2 should have a rebuild kit:
http://www.crc2onlinecatalog.com/

It's VERY important to do this job EXACTLY right, but it's also a lot simpler than it looks once you take everything apart and see the parts firsthand. Just make sure you keep track of what goes where and in what orientation.
 
It could be ither one, but I've heard of the little hole getting pluged more often then the piston sticking. I know the information about cleaning the little return is on CB1100f.net.

If you have the MC that has the plastic tank I would just get a new MC from Partsnmore.com. They have a Yamaha unit listed as a universal, that is if you have double calipar brakes. If you have single calipar brakes the I believe they list one in the SOHC Honda 750's.

Get new fluid in there and take it easy for a run or two.

As to the brake lines, here is a little experiance of mine, my dad has two honda ranchers, on is an 01 the other is an 05. Both bought brand new, never had the brakes touched. I couldn't believe the difference in the feel of the lever, the 01 will go down to the handle bar with little problem, the 05 will get nice and firm after a short travel. Rubber brake lines don't even last 5 years, so get some new ones at the least.
 
The brakes are FIXED!! I took apart the master cylinder and cleaned out all of the "rock candy." Put it back together, primed it, hooked it all up, bled the brakes - we now have perfection! I may still tear into the calipers, but for now I am very happy. This is my brother's bike, so maybe I'll have him do the calipers :D

Thanks for the help folks! Now to figure out why the throttle has a flat spot.
 
Calipers are a nice weekend project, and rebuilding them is peace of mind.
FYI to my total amazement when I was rebuilding the calipers on my 83 750, genuine Suzuki parts prices are actually on par with the popular K&L rebuild kits. Anyhow, I believe the same calipers were used on the 750E models from 80 - 83. And the fluid seal, dust seal AND BRAND NEW PISTON for each caliper was something like 28 bucks........ I couldn't believe it.

I got that price from www.crotchrocket.com

And to think.... when I had to rebuild the the calipers on a 81 CB650C last winter, I had to scoff up a whopping 80 bucks PER caliper just for the darned piston.
 
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