Reservoir holes (front brake)

[Guest]

My front brakes have been dragging occasionally over the last two or three months. It got to the point that the front wheel was so locked that I had to open the bleed bolts to release pressure just to get home.

So . . . yesterday and today I have taken the front calipers off, pulled the pistons, cleaned everything, lubed the pistons, and the brakes are still dragging. So . . . reading on these forums someone suggested to someone else that their problem was their master cylinder having a clogged "suction" hole. I don't know which one is the suction hole but it must be the one towards the front or, looking at the pictures, to the right. It doesn't seem clogged so much as it looks like it has a piece of machined aluminum in it and there no way to get to it that I can figure out. Somehow their must be a way to remove the master cylinder piston but it doesn't seem obvious and my Clymer or whatever it is book doesn't break things down that far.

I've used wire to dig at it and air pressure into the outlet to try and blow the obstruction out. It looks like it's aluminum just like the reservoir itself so I'm thinking I simply just don't know what I'm doing.

Here's some pictures of what I've got. Can anyone identify or explain why that first hole looks like it has a piece of machined aluminum in it? It looks like it's part of the reservoir case instead of some crud that got caught in my return (suction) line.

I'm at the point of thinking I need to pull the master cylinder if only because if I drill this hole out, there's going to be a burr on the bottom of the hole that needs to be removed so one way or another the piston & spring needs to come out. Right?

Help please. This is a 1982 GS850G.

MikeRes2.jpg

Okay. In my shop manual which covers all of the GS850's from 1982, it says there is a circlip holding the master cylinder piston in. It ways it requires a special tool to take if off and not to use the old one when putting it back together.

That return (suction) hole is the problem the piston isn't sucking fluid back into the reservoir thus causing pressure to build in the lines and calipers which causes the dragging and the locking. So I'll drill that damn hole out if it comes to it - wire and everything else I've tried isn't working . . . but I'm sure a drill will work. I don't think the piston actually extends all the way to that return hole so maybe the drilling burr won't interfere - at least until it breaks off and lodges down in the caliper pistons.

Does anyone agree with me that I need to drill out this strange piece of aluminum that appears to have been cast into the reservoir when it was built - obviously not since the brakes have been working fine.

I noticed in taking calipers off that pads on the left side still look brand new while the ones on the right are well worn. For some reason, my brakes have just been working on the right side all this time. I never noticed. I've changed out my rear pads a couple times over the years but this is my first exposure to the front brake system.

Please see the post below this one for a second picture of the reservoir holes.

[Steve]

"The post below" will only happen IMMEDIATELY after you posted this one, and then, only if you do it in the middle of the night, when NOBODY else is posting.

You will be better off copying your second thread, posting it here, then deleting that one, to avoid confusion.

Now, to your problem:
You do NOT have an aluminum restriction in that hole. That is the aluminum body of the reservoir. It is machined down a bit and has a VERY small hole at the bottom. If your brakes are dragging after riding a few miles, THAT is the hole that needs to be cleaned. Do whatever it takes to clean it, do not drill it out, unless you have VERY small drill bits. Typically, the smallest drill bit in a set is 1/16", that is much larger than the hole. What I usually use is a single strand of copper from a 14- or 16-gauge wire. Some brands have different numbers of different-size strands to make up their wire, so you might have to search a bit to find one that works.

There is nothing in the bore inside that hole, so feel free to poke away to get in there.

.

[MikeS]

This is a clearer and closer picture. Thanks for the info regarding the nature of this hole. I can see the tiny hole you are talking about so need to find something small enough to get into it. I've got some valve adjustment clearance wires around somewhere which, if I can find it, should have something small and strong enough to poke around. I'll try air again, now that I can see there's a hole there. Funny . . . it wasn't visible yesterday when I was fooling with this. I guess I wasn't looking for something that small.

[Steve]

"Clearer and closer" is always nice, but you still need to clean that little hole.

.

[MikeS]

This is a clearer and closer picture. So far no luck puncturing what appears to be solid metal.Res1.jpg

[MikeS]

Assuming I eventully get tht hole unplugged - just a matter of time - I've got pads on the left caliper tht look brand new after something like 40K miles. The ones on the right, one is worn normally and the other is badly worn, but still showing a gap in the center line. I don't remember changing out these pads, but could have. Need to look in my maintenance log.

Question: What is responsible for determining fluid quantity to the two reservoirs? Should I take my lines off and blean them, along with the manifold fittings? Seems like the mors I get into this the more thorough an overhaul I need to do. Something is directing more pressure into my right caliper than my left one.

Rear brake has been a real trooper. Occasionally new pads but I don,t recall even changing fluid in the last five yers. I'll surely get around to flushing my rear brake system after dealing with these front brakes.

Mike
GS850G - 1982 & 1979 before that (still sitting in the back yard - blown head gasket)

[Steve]

Believe it or not, Suzuki recommended changing brake hoses every two years. I am willing to bet that very few bikes have had that done. Yes, I am guilty of that, too. An internally-plugged line will keep fluid from flowing.

Rather than discover what else you might have to do, why not just start from scratch? Rebuild the master cylinder, rebuild both calipers, replace the hoses, DONE.

.

[storm 64]

Steve, I know the factory stock brake lines should be replaced every two years. My question is, how often should the "new" braided type brake lines be replaced? I would think they'd last much longer. I never made my own lines, what type of hose do they use?

[Steve]

It is my understanding that the stainless lines last forever.

.

[MikeS]

The brake line to my left front caliper isn't blocked. With both bleed valves open, squeezing the lever squirts fluid equally out of both holes. Taking the piston out and cleaning as I did yesterday may fix that problem. It wasn't pitted or rusted on the outside but it wasn't perfectly smooth and clean either (but now it is), so we'll see.

Today, putting air through the fluid outlet on the reservoir, I feel air coming out of the "tiny hole", so it's not blocked. It might have been blocked before, or not . . . I never even noticed the tiny little hole until I blew up that picture I posted.

Onward. I saw somebody say mixing oil and brake fluid is likely to cause some kind of disaster . . . actually some people recommend using mineral oil instead of brake fluid, so I don't immediately see how getting the two in contact with each other could be all that serious. Looking at my can of brake cleaner, it does say not to use kerosene or oil or gas to clean brake parts, so somebody is correct.

My shop manual does say in big bold letters to change out the brake lines every two years. Seems excessive. I got by for many years with just a coaster brake on the rear wheel, so I'm not so sure a front brake is all that necessary anyway.

It could be that the lines need to be strictly rigid and not subject to swelling for the fluid return function of the master cylinder to work properly. I'll find out shortly.

[Rich82GS750TZ]

Seems excessive. I got by for many years with just a coaster brake on the rear wheel, so I'm not so sure a front brake is all that necessary anyway

Wow. Far be it from me to tell anyone else how to do anything on a motorcycle. I just don't Understand that statement at all. I rode my dirt bike in the soft stuff that way when I was a kid but on a street bike It is generally accepted that approximately 70% of a motorcycle's total braking power comes from the front brake and only 30% from the rear brake.

[Steve]

I got by for many years with just a coaster brake on the rear wheel, so I'm not so sure a front brake is all that necessary anyway.

On a 30-pound Schwinn, yeah, no problem. On a 600-pound Suzuki, ...

Well, let's just say that I'm glad I won't be in YOUR neck of the woods any time soon.

.

[Big T]

Replace the brake lines and rebuild the calipers. The seals ate 37 years old

And, thoroughly clean off any oil on every brake part

Clean the slides so the pads can move

[greg78gs750]

given proper maintenance, that is....i know you know this, steve, and MAYBE it goes without saying but....

It is my understanding that the stainless lines last forever.

.

[TxGSrider]

Wow. Far be it from me to tell anyone else how to do anything on a motorcycle. I just don't Understand that statement at all. I rode my dirt bike in the soft stuff that way when I was a kid but on a street bike It is generally accepted that approximately 70% of a motorcycle's total braking power comes from the front brake and only 30% from the rear brake.

I read somewhere that that figure can actually be low... on many late model sport bikes the are capable of "stoppies" (braking so well that the rear tire comes off the ground) in that instance the front brakes are 100% of the vehicle's stopping power. Just food for thought. Regardless, front brake are darn important!