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have been trying to clear this now for over 2 weeks off and on, wire from a wire brush wont clear it, using brake cleaner solvent wont clear it and using nnedles or pins wont clear it.

Has anyone had to resort to drilling this hole out ?


I have a very fine drill, probably about 1/64" at a guess, if I do this will I cause problems ?

On my master cylinder there is a supply hole for the fluid to go out of and a depression where I assume it is allowed to return through to allow the brakes to come off, will drilling a largere hole cause problems
 

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In a word, yes, it will cause problems. If the hole is enlarged much it will allow too much fluid to be pushed back into the reservoir when you squeeze the lever. In the US it's fairly easy to get some very fine drill bits at Harbor Freight or a Model shop. I've purchased drill bits in a hobby shop that were as fine as a wire brush bristle. One of those in a pin vise would do the trick on the master cylinder.
 

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I may have a similar problem. Do your pistons retract after the squeezing the brake lever? Or... How much resistance does wheel have when you try to rotate it. The only thing I've done so far is flush my fluid. I would think if the return hole is plugged, the wheel would remain locked. Thanks.
 

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There shouldn't be much resistance to turning the wheel by hand. You won't be able to spin the wheel much but it should turn fairly easily by hand. If it takes much effort you probably have a dragging brake.

The pistons in disk brakes don't retract like shoes do in drum brakes, they release the pressure but don't move back. If you have a much drag on your wheels when the brakes are released it's likely the calipers are frozen. It's not uncommon for the sleeve that passes through the mounting hole in the caliper gets corroded and freezes solid in the caliper. The caliper has to be free to move from side to side a bit to even up the pressure when the pistons extend. The pistons press their pad against the disk and the caliper slides outward pulling the inner pad against the other side of the disk. If the caliper is stuck it can't release its pressure against the inner pad. A stuck caliper is usually easy to spot, one of the two brake pads will be worn much more than the other.

The only cure is to remove the caliper, press the sleeve out and clean the sleeve bore in the caliper and the outside of the sleeve, re-grease liberally and remount the caliper.

If the small port in the master is plugged a couple of things can happen. The worst is that when the brakes heat up and expand the brake fluid the pressure will build up and tighten the brake caliper which generates more heat and increases the pressure until eventually the brake locks the wheel. The small port is there to relieve that pressure and allow expansion of the fluid to pass back to the reservoir. The other problem with a plugged small port is it becomes nearly impossible to get all the air out of the system when you bleed the brakes.
 

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Just a thought, how about using an acetylene torch tip cleaning tool, it will contain quite a variety of sizes and the wires won't break if forced, they are quite flexible.the wires havea file like edge, john
 

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Might work but my torch tip cleaners don't go down small enough and one is a #0000.
 

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I had the problem when I first got my bike. I removed fluid from the master cylinder took 1 piece of wire from a wire brush put it in a small pair of vice grips and cleaned out the hole that looks like a depression. Then I removed the front calipers and moved the pads and pistons back with a c clamp you will see fluid back in master cylinder remove that fluid and clean out master again with wire. reinstall calipers fill master and bleed new fluid through them.
 

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by the looks of the fluid when i removed the master it had been in all it's life, will just need to keep spraying brake cleaner and keep trying with a needle etc
 

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I've just had to deal with that problem.

I rebuilt (thoroughly cleaned) the m/c from an '80 GL1100. When reassembled it pushed brake fluid out when I pulled the brake lever in but sucked it all back again when I released the lever. The main fluid hole was just fine but I could not tell whether the second drilling was meant to go all the way through to the bore or not. I scratched around with various pieces of wire, all to no avail.
I finally got the finest needle from the wife's sewing kit & inserted it as far as it would go. It got quite a bit of hard corrosion type solid out & I was able to finish the job with pieces of copper wire from an electrical cable.As far as I know, I have not enlarged the hole.

The m/c now works fine!!

I lost a lot of sleep trying to figure out why it sucked the fluid back & the fluid level in the reservoir did not go down...the hole was plugged solid.
 

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On a friends bike, I have used a small drill bit with a hand drill turning slowly to get the majority out. I finished up with this. The next day all was right.

I assume that you are unable to force the gunk out with compressed air or the brake pressure. Do remember to put the caps back on so that you don't have this problem in the future.
 

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I had a similar problem with my bike, and it turned out to be a "sticking" piston...Probably not the same as yours, but just a thought..
 

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ok guys, many weeks after the original post I finally managed to clear the hole

I tried everything, tried to drill with a 1mm drill, broke 2 and gave up. Bought a wire brush, cut off 3 strands and managed to bend 2 of them into all sorts of shapes

Decided to remove the reservoir seal and place in a pan of boiling water, boiled for about an hour off an on, take out and try to poke through using various bits of wire and needles

Eventually managed to get it clear and can now shine a light through the hole - result !

Now for the bad part, Friday morning I thought I'd nip out on my GS500, hadn't been used for 3 months as have been using a Ford Ka, 2nd junction 400 yds from home, fully kitted except for overtrousers and the front wheel locks up and washes out from under me, down I go at 2 or 3 mph, left leg trapped under bike.

Pulled myself clear and then got up to find chest pain and unable to breathe deeply, with the help of a car driver I picked the bike up, tried on my own no strength, damage is scraped and damaged fairing where indicator pushed through, various grazes and left hand mirror broken

Now, I think the brake had stuck on and caused the crash but when I set off it was free and when we picked it up it was free, I'm blaming the damp road with mud on it, whatever all I can say is it hurt and went to the doctors and he says bruised ribs, will hurt a lot before they get better

plus point is take a week off work, bad point is I can't sleep on my left or right (well with pain)and if I make a claim then the bike will probably be a write off
 

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Sorry to see you are having such bad luck. At least you're alright! I hate it went you get pinned under a bike. I was pinned under my ST two years ago. My riding so-called buddies still bring up the incident. Maybe you're getting all of your bad luck for 2009 out of the way early. Glad to see you have the blockage issue squared away. I haven't rode my GL since I bled the front brakes. The back rakes works good after the flush (was locking). Hopefully I won't have to go through the hole blockage thing. But I'm ready. Hang in there.
 
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