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Hey everyone,

Advice needed on a Suzuki GN125 front brake caliper sticking. The caliper is a hydraulic fed single piston manufactured by Aisin on a Suzuki GN125 Y 2000 model.

It’s okay after being taken out for a ride for more than a couple of minutes and returns to normal allowing the bike to be pushed freely. Left standing overnight and it’s a real pain in the ass to push because the front caliper is stuck back on.

So far this is what I’ve done;

The caliper has been dismantled and thoroughly cleaned and flushed out. The piston had some gunk round it that I thought was causing the problem so that was all cleaned off with fresh brake fluid. The sliding pins, piston, and all rubber seals were fine and in good condition and so were reused. All greased with red rubber grease and reinstalled fine. Banjo washers were replaced just to be sure of no leaks. Everything was moving freely and working great now.

This was then put back on and bled, no air bubbles in the line. Checked all along the system for leaks and all was good. Brake fluid went through the line all fine so I’m assuming the line hasn’t collapsed or anything funny there. Brake pads are still good with plenty of use left on them.

The only thing I can think is that I’ve inserted the anti-rattle clip in the wrong way round or something. It doesn’t have a direction arrow on it so this was a bit of guess work. It only seemed to fit in one way. The way its installed currently has the moving brake pad (piston) pushed against the mounting bracket so that they slide together. I’m assuming this is correct as any other way left the brake pad to rattle around in the mounting bracket and just fall against the brake disk. I’ve referred to the Haynes manual on this but the diagram is very unclear on this.

Tested it a few times and lo and behold the damn thing is sticking again. Any thoughts on what might be causing this would be great as I really need to get this put in for an MOT really soon.

Thanks in advance.

Caliper Disassembled.JPG
 

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Whatever that junk was is probably back, as most likely you have a tiny leak that is attracting the junk and making it stick. This may be caused by a small score or blemish inside the piston bore, or the bore no longer being exactly round, all of which will cause a little leaking abd also cause the piston to stick.

You can take the caliper back off, buy a hone, and hone the bore. Then rebuild the caliper with an aftermarket rebuild kit that includes a new seal, checking to make sure the bore is still round and so is the piston. The rebuild kit will also include new slider pins and such, in case the caliper sliding is the problem and not the piston sticking.

Much easier to just buy a good used caliper, which can often be had for less than the price of a rebuild kit plus the brake hone over on this side of the pond. Don't know about over there, or even about your specific model, which is not sold over here.
 
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