Brakes applying their self

[rphillips]

So crazy, almost embarrassed to post. "83" GS1100E, Just riding along & bike starts to slow, more throttle just to keep speed, front brakes are tightening keeps slowing & within a half mi. or so must stop. Front brake very tight. Loosen bleeder on either front caliper, couple of drops of fluid shoots out, & all is good. Never know how long till it will happen again in a week, a month, or this time it's been a couple of yrs. This started a couple yrs. back, at that time I rebuilt the master, cleaned polished the pins the calipers slide on, & flushed & installed new fluid. Thought it was fixed till yesterday it did it again, probably been 1500 to 2000 mi. since work was done. Not to be confused it's not like use the brake & it doesn't completely release, It may be 20 mi down the rd. from last time brake was used... Shouldn't any pressure built in the caliper, for any reason, just push the couple of drops of fluid back up into fluid res. as long as you don't squeeze the brake lever???

[Gorminrider]

Two things to check:
You've heard this first one before but:

Open the fluid reservoir, remove the tiny stainless steel cap that covers the back pressure relief hole and see if it shows a small geyser as you work the brakes(often described on the forum as a problem with symptoms like yours) it can squirt right out of this tiny hole without the tiny cover on so cover painted surfaces in range and don't put your eyeball too close. The "geyser" is fairly obvious. The tiny hole can be cleaned with a tiny stiff wire.

The SECOND thing to check is replace the caliper piston seals.These can capsize slightly as they wear, and not allow a full return of the pistons with the exact symptoms you describe.
As to why it happens by itself, I'll guess that it's expansion due to warmth of the air at the Master or a slight expansion of brake fluid as it warms at the calipers.

[dorkburger]

Agreed with Gorminrider.
I had a similar problem with the rear brake a few years ago caused by corrosion in the master cylinder sleeve. The rod went in, but didn’t release.

[phydeauxmutt]

I will also agree with Gorminrider, but mainly just the first one. Never heard of the second one.

[Cipher]

Clean slider pins
Change fluid

[Nessism]

If the bike has the original brake lines it's good to change them out because a scummy scale can form in the inside and flushing won't remove it, and this scale will contaminate the fluid, even if it's fresh. Also, use OEM brake calipers seals. K&L seals are iffy at best and I've experienced several examples where the seals were too large and caused piston binding.

[Gorminrider]

I will also agree with Gorminrider, but mainly just the first one. Never heard of the second one.

Do watch for it. Motorcycle mechanic clued me in. I've done it twice, once on a rear (GS650), once on a front(Gsx400E) where the tiny relief was working ok.

The slider pins on the caliper are what I kept trying to fix without permanent result...I use "proper" silicone brake grease now, by the way.

Some Suzuki front brakes have a (problematic?) rubber collar on one slider pin and it can be the stickiest when weird grease and dirt adheres or swells it.... I don't know why they felt it was wanted -seems to be unique among my bikes.

[Brendan W]

Are both disks heating up or just one side?

[rphillips]

Both sides very hot, & bleed either side & all is good. Thank ya'll... May be a few days till I get to check it out.

[Brendan W]

Both sides very hot, & bleed either side & all is good. Thank ya'll... May be a few days till I get to check it out.

That would point to an issue on top, either the master cylinder, most likely, or the top hose internals developing a one way valve.

[salty_monk]

You still got the anti dive connected?

Check the brake pads. I had this problem with a new pad set that had slightly oversize backing plates. Was a bad batch. Unfortunately it cost me a brake rotor as I went on a 2500 mile trip with it without knowing (wasn't as extreme as yours).

[Brendan W]

You still got the anti dive connected?

Check the brake pads. I had this problem with a new pad set that had slightly oversize backing plates. Was a bad batch. Unfortunately it cost me a brake rotor as I went on a 2500 mile trip with it without knowing (wasn't as extreme as yours).

I've had a PM or two with the OP.
Anti dive is still on there and all original hoses.
Never had anti dive. Could that be causing pressure lock?

[salty_monk]

Only if the extra hose is blocked or collapsing I would think.... If it's original hoses that would be my first place to look after checking out the caliper and MC return port.