Bled the brakes, but still spongy. Lines worn?

[pnedac]

I am rebuilding a GS750 1980 and I will say that when I got the bike thebrakes were ruined. I had to rebuild all the calipers completely and though the lines looked fine as did the master, I did not replace those because they aren't leaking or anything and appeared to be okay. I had a brake guy come out yesterday and he too is baffled. We are just cycling fluid through with zero air bubbles and they are still so spongy. All new calipers and pads.

Could it be that though there are no leaks that the lines are simply too worn out or something? I am confident they are original. I am thinking it is the only thing left except the master, but that is clean and functioning.

Any ideas? I appreciate all the help.

Pnedac

[Agemax]

if they are the original brake lines then yes, they definately need replacing. 30 year old brake lines will flex and bulge like you would not believe, even if you cant physically see it.

replace them with stainless braided lines and it will transform your brakes.........

[pete]

So the original rubber hoses are still on there?

They are supposed to be replaced every two years... so if they're the originals (most likely they are) then yes, those hoses will be deteriorated and flexing not to mention potentially dangerous.

Do yourself a favour and get braided steel lines.

[pete]

Snap Agemax

[pnedac]

You have all confirmed my suspicions. Yes they are original and yes they will be replaced. I will report back with the results. Thanks. I suspected they are bulged out and not enough of the pressure can get through. Thanks boys!

[pnedac]

http://www.ebay.com/itm/APEX-Stainless-Steel-Braided-Brake-Hose-Line-Lines-Suzuki-GS750-ES-GS-750-/190827484869?pt=Motorcycles_Parts_Accessories&hash=item2c6e3456c5&vxp=mtr

These say they are for a 1986 GS750. You think I could use them on the 80? I tend to see that most brake lines are about the same. This one has 3 up front and one rear like the 1980.

If not any economical alternates that you know of? The OEM ones are very expensive! Kinda poor over here ya know?!

[pete]

Get those ones, just confirm all the measurements when you order.

I got mine from him (just a single front line on my 450) and am very happy with the price and quality, and a number of other members here have bought them as well.

[pnedac]

Fantastic! Thanks for that bit of info. I see that we can choose colors too, which is great for this project.

Thanks again guys.

[pete]

No worries, be sure to post pic's when done!

[subforry]

I recently become a stainless steel brake line believer.

There might be a few things besides the lines. Make sure the caliper pistons are not binding. Check to make sure the do keep the pads against the rotors and not slipping back into the caliper.

The next item is more a hypothesis, but I think that it is near impossible to get all the air out on the first bleed after opening the system. If safe ride the motorcycle then go for a short trip and let it sit over night then bleed again.

[nick1000]

Pnedac...Before I went through my 1000 (it had been sitting for 13 years) I called Carry Andrew at Hypercycle with a few questions. He told the usual stuff about cleaning the calipers, etc, etc, but then said that the master-cylinder will need to be rebuilt, guaranteed. He said I'll get all the air out but then won't be able to get good feel or power...turns out the national champion tuner was right.
I haven't rebuilt it yet and may try to "hone" things and see if I can get it better...I've never messed with the inner-workings of a master cylinder...but perhaps Carry's info will help your problem...NI