HELP,,,,,,,,Soft rear brakes on 2002 RSV

[maddog2498]

I have a 2002 RVS, with 135k and my rear brakes are soft and will not slide rear tire. I put new rotary on rear app 40k miles ago when I put on new tire, and they were a little soft but would slide wheel if I tried. About 16k miles ago I put on new rear tire and when I got it back together they, I bled the brakes, but they were a little softer than the last time, but I could still slide rear if I tried. I just put on another rear tire. This time I use a 1 man vacuum bleeder and still pump brake to bleed them the best I can. When  rode today I could not get the rear brakes to slide the tire. It has stopping power but very soft. Now the rotor that I put on was an after-market. I notice my old OEM rotor was app 7mm thick and was worn down to 4mm. The new after-market rotor was only 4mm thick brand new. Do you think this is my problem. Any help and advice will be appreciated. thank you

[Freebird]

I’m not sure.   Certainly sounds like the new rotor is too thin but could also be other things.  You said you bled the brakes but how long since a complete fluid change?  At those miles, I would hope that has been done.  Other than that, which is the first thing I would try, it could be your master cylinder 

[M61A1MECH]

Have you flushed out the brake fluid to ensure there is no old contaminated fluid in the system?

Have you inspected or rebuilt the rear master cylinder?

Try getting a speed bleeder for the rear bleeder port, those work great make bleeding a breeze.

I would also consider going back to OEM rotor, you can check the specs on the rotor thickness requirements in the service manual found in the tech section here on the forum.

 

Well I see Freebird beat me to it as I was typing.

[maddog2498]

1 hour ago, Freebird said:

I’m not sure.   Certainly sounds like the new rotor is too thin but could also be other things.  You said you bled the brakes but how long since a complete fluid change?  At those miles, I would hope that has been done.  Other than that, which is the first thing I would try, it could be your master cylinder 

I have not done a complete fluid change. Never have done one, but maybe that is the time. With my vacuum pump, I never could get a complete stream of fluid. Never had fluid go bad. Thank you.

[M61A1MECH]

Brake fluid is hydroscopic, meaning it has a affinity to absorb moisture, water although considered to be an incompressible fluid, often has dissolved air in it, that dissolved air is compressible.  Just as a note, Honda recommends the entire brake hydraulic brake systems on the Goldwings be flushed and replaced with new fluid, every two years, that system is a bit more complex that that on a Venture, but replacing your brake fluid at some regular interval be it time or miles, is a good thing to do. Again Speedbleeders make that job way easier to do, just pump the old fluid out into one of their catch bags using the lever or pedal depending on front or rear brakes, refill the master cylinder before it is empty and your done in no time.

[maddog2498]

OK. I drained and ran new DOT synthetic fluid today. Still can not get full pedal. Rode the bike and it will not slide tire on dirt road. Looks like there is still air coming out while using the vacuum pump. Why is that? Is there a trick to bleeding to get air out. As I said every time I change a tire off, my brake pedal got softer. Does the rear brake pedal operate just the rear or is it like a goldwing, front and back?

[Freebird]

The brakes on the RSV are not linked.  

[Freebird]

The brakes on the RSV are not linked.    Take a look at this thread.

 

[maddog2498]

49 minutes ago, Freebird said:

The brakes on the RSV are not linked.    Take a look at this thread.

 

Did he rebuild it??? Did it correct the problem??? thank you

 

[Freebird]

 I, he did not in this case.   Just the rubber diaphragm and slipped down. 

[maddog2498]

On 8/16/2025 at 7:43 AM, Freebird said:

 I, he did not in this case.   Just the rubber diaphragm and slipped down. 

OK. I drained and ran new DOT synthetic fluid today. Still can not get full pedal. Rode the bike and it will not slide tire on dirt road. Looks like there is still air coming out while using the vacuum pump. Why is that? Is there a trick to bleeding to get air out. As I said every time I change a tire off, my brake pedal got softer. 

I have fluid coming using my vacuum bleeder, but it still looks like air bubbles coming into line from the bleeder valve. I took bleeder valve out and put thread tape on, replaced and still looks that way. I have never done brakes other than pump and bleed on cars. Is there sometime I am over looking or a trick to bleed. I read somewhere about someone using what they called reverse bleeding, where you force fluid back into the reservoir thur the bleeder valve. I'm at my wits end. Any suggestions will be appreciated. If you know of anyone on here that could help. Thank you in advance.

[luvmy40]

It is possible that you need to rebuild the master cylinder. It's not a difficult or expensive job, but sometimes necessary.