Brake pedal little resistance

[Solo So Long]

I just brought home a 1989 1500.

Part of the reason that I got it at a good price was that the former owner was riding it several weeks ago and lost rear brakes. The pedal goes all the way down. The fluid is up to the marks on the reservoir. Pumping doesn't change anything.

Having never worked on a brake system which does both front and rear from the pedal, is there anything that I should know before I dig into this? I suspect that the master cylinder needs a rebuild (replacement?), but is this a common problem with a procedure or cure that goes off in an unexpected direction?

[bluthundr31]

What does the fluid in the reservoir look like? It needs to be clean and clear. It'll turn rust/brown in time so if you can't see through to the bottom of the reservoir, it's time to change the fluid.

If the fluid is new, it time to bleed the brakes to ensure there isn't air in the lines causing the loss of brake pedal. Bleed the left front brake first, then do the rear brake. Speed-bleeders are a life-saver if you have nobody to help with the bleeding.

Check the brake pads to make sure they're still serviceable, , , replace them if they're toasted.

Check all fittings and hoses for looseness, and wear.

If all this is done and you STILL have issues, , , the master cylinder might need to be changed/replaced.

[Solo So Long]

I'll try bleeding first. Roger that on the Speed Bleeders, I've used them before and they are a Must Have for anyone with fewer than three arms.

Thanks!

[bluthundr31]

Make sure its DOT4, , , some folks say you can use DOT5.1 (NOT 5.0) too, , , but I've stayed with DOT4.

[Solo So Long]

Thanks for the tip. I know about DOT4 vs. DOT5.x . . .I'll stay with the stuff that I know is right.

[CrystalPistol]

I've used SBs, not impressed with longevity and they require a no leak thread. I have better luck vacuum bleeding with grease on the threads if needed to kill air being drawn in, or "pump up-hold-open/shut-pump up" method. Just my experiences.

Rebuilding the rear MC is easy, it's getting to it that's a PITA. Guy on you-tube demos doing a refresh with rear MC on the bike, but I lost the link. WingAdmin might have something on it. Afterwards, need to bleed "rear -left front - rear - left front - rear … a couple few times, air like high places and that brake line from rear MC to left front is long and goes up high on the frame before going to left front caliper.

First though, use a weight or custom stick as a wedge or bungie cord to center stand to pull rear brake pedal down with rear MC reservoir topped off, tie down … and leave it a day or so. I scoffed at it, but it worked on our '97 and a buddy's '96 after sitting a long time, don't know why, several theories floating, but try it.

[Solo So Long]

I'll try that, because it looks like I'll have to take off the left saddlebox to get to the bleed screw. The hole with the rubber grommet goes to a 10mm bolt.

[ct1500]

Bleeding the 1500 brakes when they have gone dry can be a real PITA to get the fluid up and over to the front caliper. I suggest starting at the rear, with that done then all pedal stroke is pushing fluid forward only. Always finish up at the rear.

[minimac]

Make sure its DOT4, , , some folks say you can use DOT5.1 (NOT 5.0) too, , , but I've stayed with DOT4.

DOT 5.1 is an upgraded(higher temp) DOT 4. DOT 5, while having the same temp rating as 5.1, is an entirely different animal. Why they labelled it 5.1 is anyone's guess. It created a lot of confusion.

[TwoTone Trike]

I don't know. I thought dot 5 was what it called for.

[MikeB]

I don't know. I thought dot 5 was what it called for.

That may be true for Harley-Davidson.
But not Honda. Honda calls for DOT 4.

[TwoTone Trike]

Thanks MikeB, I stand corrected.

[Solo So Long]

Just FYI, weighting the brake pedal for a couple of days did nothing. I pumped it a few times this morning and put the weight back. If no joy by next payday, I'll buy Speed Bleeders and get that done.

[HandymanHerb]

I got a good deal on my 97 because the brake peddle was soft and not working,I read up in my shop manual and seen the foot brake activated the left front and the rear caliper, So I went to the front with the speed bleeder and sucked all the old stuff out and added new dot 3/4 fluid in and bled it out.

Had some peddle, couldn't fit the speed bleeder through the hole in the side bag, so pumped up the foot brake and put a weight on it and bled the rear that way, I had full brakes and didn't have to spend on anything but Dot 3/4 fluid.

So I got to ride it with all the brakes working for the first time, I replace the right front disks when I put the new tires on a few weeks later, they were worn out, the left and rear were done 10000 miles back and still good

[CrystalPistol]

Just FYI, weighting the brake pedal for a couple of days did nothing. I pumped it a few times this morning and put the weight back. If no joy by next payday, I'll buy Speed Bleeders and get that done.

Even with the weight, will still likely need bleeding rear - front left - rear in that order.

Friend of mine has a friend owned a GL1500 had spongy brakes, leaking fork seals were so bad brake pads were wetted too so I was asked to help out fixing. Come the day when all parts were collected, met at my friend's carport, did the forks, bushings & seals and new front pads. Rear pads were OK. We changed out fluid, then bleeding started. Had a tough time getting good pedal, had to do two cycles like this: "rear - front left - rear -front left - rear" but then it had a solid feeling good pedal.

When doing the rear, I lay on my back below the rear of the left saddle bag, reaching up with a bleeder wrench, mostly by feel, to open & close the bleeder while holding hose on it. My friend was on the right side of the bike tending to making sure reservoir was near full and he was operating the pedal. "Pump" I'd say, he'd pump 3 or 4 slow strokes, then he'd hold it down and say "Holding" and that was my cue to open the bleeder and let pressure escape, watching for bubbles then close it quickly, once closed, I'd say "Pump" and he'd pump it up again, watching that level.

Do it until there are no bubbles, just clean fluid coming through the clear bleeder hose. A jar reduces mess. Then do left front, then rear again.