Some original OEM brake stuff does not work as well with Dot 5 when it came with dot 3 - but may be that’s just in jerzey

 

Dot 5 color when fresh and not full of water that is has collected from the air humidity,



So yes, your fluid need to be power flushed in the brakes to replace the water contaminated fluid in the first place.
Note, since it not hard to power flush the brakes, I power flush my brake lines yearly with new Dot 5 every time.
Also, with seeing pieces of rubber in the fluid, the reason that I would pull the caliper and plungers out, to clean them up and the channels, before power flushing the system as well.

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As for back to the question at hand, and since your fluid looks like it has not been changed in years and has rubber pieces in the fluid, I would go the deep end for corrections.

Would start by removing the lines from the calibers front and back, and just allow all the fluid to drain out of them to start with.
Next, would pull all the calipers off the bike, so you can pull the pads and get them off the sliders pins as well.
At this point, would use compressed air to pop the pistons out of the calibers, to get each piston in hand so you can take a cloth to clean out the caliper piston channels and all the crap that has collected in them and on the side walls.
On pistons, take a good look as the seals, and may not need to replace them, but would at least pull the seal and the dust boot off, clean the piston, and on the seals, use dielectric grease or fresh dot 5 (both are silicone) to give the rubber parts a light coat, wipe that off and the rubber derbies that will come with it, then another light coat to the seal and boot, put the seal and boot back on the piston, light coat of silicone lube to the inside of the caliper piston channel walls, reinstall the piston back in the caliper. From here, good clean up of the pads if they do not need to be replace with spray brake cleaner, then brake grease to the back of the pad, and the sides of the pads. As for grease on any rubber parts, like the O rings for slider pins, do not use Petroleum based grease since it will cause the rubber to swell up/cause binding, so only silicone (dielectric) grease when it come to any of the rubber parts.

https://partsfinder.onlinemicrofiche...davidsonmc/259

So really, since brake grease is really silicone anti seize grease, short of piston assembly 5and 10 parts and light layer inside the caliper piston channel before you restall the pistons with clear dielectric grease, pins 4 into rubber insert 3, anti shim 14 front and back, back and sides of pads, and a touch on the spring shim 2 for its legs that goes into the caliper backer plate channel.
Note, on pins 4, I use a drop off loctite on the thread when installing them,so don't get lube on the thread part of the pins.

Same goes for the front,


On the front brake lever, since we are going to replace all the fluid it fresh fluid,


Will pull assembly 19, to clean those parts up via silicone method, clean the inside of the plunger assembly in the lever housing with cleaner, then light coat of dielectirc grease with plunger assembly, before reinstalling them.
Note here, if the front brake is starting get pressure with just a slight pull of it about 1/4" in, then plunger is fine. If you are having to pull the front lever say more than 1/2 inch before you start to feel pressure build up, then just replace the plunger assembly, or if you can find the seal part (is the U piece on the end just before the spring for a few dollars, then just replace it).

As for rear master cylinder,

Getting to the seal parts 26 can be a little more challenging, may want to leave it alone if the plunger assembly is not binding,and do a little extra pumping and powder bleeding, to all the new fluid to clean up that works.

From here and the brakes back on the bike, knowing that the pistons and pins are not binding, pads and shims correctly brake greased, then it time to power flush the brakes with new fluid and get in to a habit of power flushing the fluid yearly, while the fluid is still purple'ish (but just a lighter clear color).




Simply, could just be that the pads alone need to come off, so you can clean them and the anti rattle shims and springs to apply new brake grease to the needed areas, reinstall the parts and all may alright with the world.
That is if the calipers are free gliding on the pins to brackets, and the pistons are not sticking in the caliper channels from water type corrosion, which is allowing the caliper to free kick back via pads to the rotors in the first place, as you release the brakes. Also on the pedal and brake lever plungers, could be the same problem as well, with the springs not able to allow the plungers to kick all the way back back when pedal and lever are released, while does not allow the fluid in the system, to return past the plunger to return to the reservoirs.

Hence it all comes down to the amount of water corrosion to the parts in the brake system, and if I see a bike that the Dot 5 fluid is not still purple, or at least still clear, then tend to just pull the system apart to check all the parts to clean up the rubber and bearing surfaces before the water corrosion gets a lot worse, they start to just be pitted to hell and have to be replace.

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Now that is just the brake side, and we need to figure out when the last time that the wheel bearings where pulled to be cleaned/check, then replace or at least re-greased if still good, as well as the free play of the timken bearings as well (.004- .006" being ideal,since factory spec may be greater on the high side).

Simply, when the tires are replace, or at least every 30K if you re running tires that will last that long, really need to pull the wheel seals to get to the timken bearings to check them, as well as the free play of the bearings as well. JG has new seal kit for $5 for both front and back to replace the old seal, Walmart carrier red and sticky grease to re-grease the bearings, and as for free lash, all comes down to either adding or removing shims from the stack.
Note, free play is checked with all the parts dry (no grease) and once the correct spacer stack to achieve the correct free play, then bearings get greased, installed, then new seals installed.

I bring all this up, since could be brake system problem, or could be that problem with cooked wheel bearings or too much free play, hence when brake pressure is applied, enough side torque on the bearing to mask the problem with the bearings not just free spinning with not side loading isntead.

 

Thanks guys for the help.

How much brake fluid is needed to do a full flush on the brake system?

 

At most a half a bottle... Just make sure it's Dot 5.

 

Are you sure its the brakes?

 

Top cap of the reservoir should state the type DOT fluid that goes in there.

May want to clean everything in the caliper and make sure the rotor is true as posted in the other comments.

The put a little anti squeal compound on the back of the brake pads at the interface of the caliper pistons

 

The reason I think it's the brakes, is because the noise goes away when you hit the rear brake pedal. I could be wrong though

 

Makes sense, but the reason I asked is I had a 2004 Electra Glide that made a squeal that would stop when I held the rear brake pedal. Turned out to be the little rubber isolator that mounts the mufflers to the frame.
I looked on Ronnies Microfiche at your exhaust system and your bike doesn't have the same set up so, you're probably on the right track with the brakes anyway.

 

One of the Harleys at my place gets DOT5, two of them get DOT 4, because they have anti-lock brake systems.

When it comes to brake fluid, there is no one size fits all.

The OP`s machine came from the factory with DOT 5.

DOT4 is nasty stuff.

 

Huh... I have anti lock brakes on the 1974... little single disk Caliper, with a 3/4 inch Master Cylinder...Dot5 in that too.. No Twinkys on the Farm...LOL