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stuck caliper (I think) rebuild time ?

SidewaysInto3rd2010-06-22 16:13:52 +0000 #1
I'm new to riding and bikes.

I'm currently working to get my buddy's 93 Kat 750 road worthy after its been neglected and sat for 2 years.

The master was full of gunk, so I cleaned it. I flushed the brake system (it had no front brakes) when I first picked it up. Now the right caliper drags so much its actually very hard to push the bike. The brakes work like a charm though !!

Anyway, I take the caliper off (the drag goes away so I know its that caliper). I take off the pads, spray some cleaner in there, put it back together, same deal.

I take it apart again, this time i squeeze the brakes, and the outside pistons move 2x as much as the inside pistons.. I try to push them back in and its very difficult so I cheat and open the bleed valve, push the pistons back, spray more clearner, put it together and same same ..

The pistons looked clean, I also cleaned the rods that hold the pads in.

Is there any other trick? should I buy a rebuild kid and take the caliper apart ?

Thanks for your advice !

mcaswell2010-06-22 16:24:31 +0000 #2
When you squeeze the brake lever does it spring back out? Sometimes the moving parts in the master cylinder need a good cleaning before they'll work right. Otherwise you problem is probably the caliper.
SidewaysInto3rd2010-06-22 16:48:40 +0000 #3

Originally Posted by mcaswell

When you squeeze the brake lever does it spring back out?

When I squeeze the brake, the pistons get pushed in, but they do not retract. It's also very hard to push them back in by hand, I had to open the bleed valve.

The front brake works like a charm.. it just seems that the pistons stick.

The master had lots of gunk in it, probably from 5-6 year old brake fluid.. I used this caliper to flush the lines after I took the master off to clean it. There's probably some gunk inside the caliper.

I'll tear it apart tomorrow. Might not even need a rebuild kit .. might just need cleaning !
mcaswell2010-06-22 16:39:32 +0000 #4
Yea cleaning definitely can't hurt. I used to have a 92 Katana, and the front brakes gummed themselves up a couple times after I let it sit too long.

The fix was to get clean fluid in the master, then pull the brake line off the end of the master and work the piston back and forth a few times with the help of a screwdriver to make sure the clean fluid got everywhere in there. Then I'd put it back together and run fresh fluid through the system.
SidewaysInto3rd2010-06-22 17:11:02 +0000 #5
I ended up taking the calipers to modern motorcycling to get them rebuilt.

I took the sticky one off and took it apart. Managed to get 2 of the pistons out and there was so much coagulated brake fluid and gunk under them I decided to get both rebuilt. I couldn't get the other 2 pistons out and have no air tools unfortunately.

Modern happened to be on my way home from work so its convenient. Anyone here get work done by them ?
CaribooBC2010-06-22 18:02:19 +0000 #6
Another Modern thread
SidewaysInto3rd2010-06-22 19:07:51 +0000 #7

Originally Posted by CaribooBC

Another Modern thread

wow ... i guess there are some less than positive reviews of modern out there lol!

well, I'll have my own first experience when I pick up my calipers tomorrow.

which one is aaron ? so I know who to talk to next time I go there.



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