Rebuilt front brakes binding- Wisdom needed.

[MAC10]

I am just breaking in a newly rebuilt set of dual calipers. Stock dual discs on a 78 GS1000, a pair of the round pad stock calipers.The smaller diameter pistons, EBC pads. Rebuilt with OEM parts. Added a dual piston size master cylinder. New braided lines, through the stock splitter.

Only have about 60 miles on the new set up. Going easy, and gradually pressing harder to give the new pads time to bed. No problems till now

This evening I parked the bike in hot sun for an hour. When I started off I noticed the lever very hard, and the brakes binding hard. Not quite seized.The rotor got a little brown, and there was a smell of hot brakes. Rotors hot to touch. I only rode about half a mile . It eventually loosened up (cooling?) and I got it home 2 miles. At home, everything normal. No damage, except a streak of pad on the rotors.

I have checked everything, and all now seems well. What happened here? Is this normal as new brakes break in?

I have the original single disc setup, and rebuild parts for it all. I can pull the double calipers and master cylinder, and go back to a single disc set up until the mystery is solved, if I have to

Wisdom is most welcome. I plan to ride tomorrow to shake it down further. I have a four day trip panned later in the week, and I need this sorted before then.

[BassCliff]

Hi,

Any water in the brake lines can cause the symptoms you describe.



Thank you for your indulgence,

BassCliff

[almarconi]

Did you lubricate the caliper pins? The calipers have to be able to slide. Make sure that the caliper bolts are not too tight, the manual should have a torque spec.

Also make sure that the calipers are square with your rotors and not cocked to one side. Check your rotor and make sure they are not warped. The wheel should spin freely with only a slight drag from the pads.

[MAC10]

The caliper pins are well lubed, and I checked everything for square and torque. Water is a strong possibility given how wet it has been around southern BC

I took my first test ride in the rain. I guess the little rubber cap on the bleed nipple, or a faulty boot could allow water in?

[Nessism]

Did you clean the master cylinder out? There is a super small hole that needs to be open otherwise things like this occur.

[jwhelan65]

Did you clean the master cylinder out? There is a super small hole that needs to be open otherwise things like this occur.

Agreed sounds like the problem is intermittent, which may indicate something is floating around inside the caliper blocking the opening. I would completely disassemble the caliper and check for pitting in the cylinder bore where small particals may have flaked and clogged the small hole there as well.

[jetta90]

Time to check things out again per the comments made up upthread.

Also take a look that the dust seals on the caliper pistons are not binding up between the piston and calipers.

Where in southern BC are you?

[SqDancerLynn1]

MY vote is for the master cyl. it is not allowing the fluid to return to the
reservoir

[MAC10]

2 new questions

Thanks everyone. I suspect the return hole in the master cylinder is blocked.I can't see it or get to it because the bottom of the reservoir blocks it from view.

This is a design flaw! Why didn't the #%^&* Suzuki engineers think of this!

What if I drilled a hole through the bottom of the reservoir, to expose it, and allow inspection and cleaning? Any problems anyone can forsee?

I will consider doing this to the new reservoir I have ordered, once I have a chance to see what would have to be drilled out. And where exactly to put it. And then, I would drill only the smallest possible hole. Honest.

I can estimate where the hole is right now, and maybe drill the old reservoir. If my impatience doesn't pass...


The second question is to do with correct assembly of the round brake pads. One is held by a screw, and is fixed to the main caliper body. The other fits in the hole in the caliper arm. The piston presses directly on this one. It floats in slight contact with the rotor. My question is- does it install fom the rotor side, or the outside of the hole?

[Runningdog]

The reservoir is removable, just remember to install a new o-ring when you put is back together...that little plastic flap on the bottom of the reservoir covers the return hole.

If there is still a bit of air in the system, you will see it come back up from beneath the flap when you pump the brakes, if the hole is not plugged....bit of an indicator, if all the stars are aligned...

[Steve]

This is a design flaw! Why didn't the #%^&* Suzuki engineers think of this!

Oh, but they did.

Have you ever read in the manual where it says to "change the brake fluid every two years"?

That is what keeps that hole from getting plugged up.

.

[MAC10]

Thanks for that. No doubt this old mc was stored and not well maintained.

I presumed too much from a non rebuilt old part. I have learned. I humbly apologize to all the Japanese engineers here.

Being curious and rational I still wonder why did they not think of making this tiny hole visually inspectable and cleanable without major disassembly?

[tkent02]

Probably because they thought it should be disassembled and cleaned every once in a while.