1998 Rear Brake Failure / Questions / Ideas?

[JimMoore]

Hi Folks,

 

The rear brake on my 98 5th Gen has given up the ghost. It goes all the way to the down stop without slowing the bike at all. I bled the rear brake. Got some air out, but the issue did not resolve.

 

First, a quick question about the system. My understanding is that the front is linked to a piston in the rear caliper, but the rear brake is simply a standard rear brake. It functions and bleeds like any other rear brake. Is that correct? Or should I try bleeding at the other ports?

 

With that in mind, I'm thinking that I have a bad seal in my rear master cylinder. There are no leaks or anything like that. Does that sound reasonable? Has anyone rebuilt a rear master cylinder? Any tips or tricks? I see some kits for sale online. Any recommendations?

[expvet]

If you bled the brakes correctly as shown in the service manual and in an excellent how to post you would see that the left clutch lever side front caliper makes the center rear caliper piston extend when the front one is pushed in. Using the rear brake pedal and the SMC (secondary master cylinder) at the left front caliper, you have to first bleed Proportional Control Valve near the battery, then the rear caliper using the padal and SMC via one rear bleed screw, and finally a typical rear caliper bleed with just the pedal. The how to link is below. Best to print it out and get familiar with it. You will need a helper for some steps.

 

https://www.vfrdiscussion.com/applications/core/interface/file/attachment.php?id=83284&key=901e1228a6eafbc7a28a50f7296c1e40

[JimMoore]

Thanks. i started looking at my manual last night and realized it was a lot more complicated that I was thinking.

[interceptor69]

Will that guide work for the 5th gen?

[expvet]

It should. My suggestion is download and compare the 5th and 6th gen service manuals. If they show the same schematic and procedure then the guide would work. Note that there is a step for ABS that would not apply to a 5th gen. 6th gen came in both ABS and non ABS models.

[Terry]

I did a poor job of changing my rear pads once and got the edge of the pad caught on the pad spring. Assembled OK but the spring would shove the pad away from the disk. That gave huge travel and little braking, even though the lines were properly bled. 

[Gaz66]

On 6/21/2024 at 11:17 PM, JimMoore said:

Hi Folks,

 

The rear brake on my 98 5th Gen has given up the ghost. It goes all the way to the down stop without slowing the bike at all. I bled the rear brake. Got some air out, but the issue did not resolve.

 

First, a quick question about the system. My understanding is that the front is linked to a piston in the rear caliper, but the rear brake is simply a standard rear brake. It functions and bleeds like any other rear brake. Is that correct? Or should I try bleeding at the other ports?

 

With that in mind, I'm thinking that I have a bad seal in my rear master cylinder. There are no leaks or anything like that. Does that sound reasonable? Has anyone rebuilt a rear master cylinder? Any tips or tricks? I see some kits for sale online. Any recommendations?

Hi Jim

Any joy sorting rear brake?

Master cyl rebuild is a good starting point, just same as doing a front, nothing special, you'll need some long nosed circlip pliers, there's a bike specific set for less than £20 on eBay.

Flushing fresh Dot4 thru is pretty easy, there's a specific way to bleed rear caliper.

Front has no fluid connection with rear, but it's linked to rear via a mechanical operation of the pivoting 2nd master cyl on left front caliper.

If you're still struggling sorting brakes, PM me & I'll talk you thru it in a way that's easier to understand than laid down in the shop manual.

 

Rgds

Gaz (UK)

 

[JimMoore]

11 hours ago, Gaz66 said:

Hi Jim

Any joy sorting rear brake?

Master cyl rebuild is a good starting point, just same as doing a front, nothing special, you'll need some long nosed circlip pliers, there's a bike specific set for less than £20 on eBay.

Flushing fresh Dot4 thru is pretty easy, there's a specific way to bleed rear caliper.

Front has no fluid connection with rear, but it's linked to rear via a mechanical operation of the pivoting 2nd master cyl on left front caliper.

If you're still struggling sorting brakes, PM me & I'll talk you thru it in a way that's easier to understand than laid down in the shop manual.

 

Rgds

Gaz (UK)

 

Hey, thanks man. I really appreciate that. I have a dozen other projects going on in the garage right now. I'll ping you when I get back to the VFR, if that's OK. 

[phoenix655]

Including the clutch I think there are 6 different spots to flush hydraulic fluid, I'd suggest just doing it all if it hasn't been done for a couple years. The service manual has a pretty easy step by step to follow. It's not really that complicated, I did it myself without needing to remove the rear wheel.

[JimMoore]

Idk if anyone remembers this discussion. I quit messing with the VFR because I had other broken things that needed fixing and my front brake worked fine. So I did what any 20-year-old squid would do and ignored it. I finally got a chance to work on it yesterday. I bled the brake from the nipple at the seat / tank junction on the right side. There was a ton of air in that line. I got it all out and the rear brake seems to be working fine. I'd like to think it's fixed, but I'm still wondering where all the air came from. I had done a full bleed less than two years ago, so it's not like the brakes had been neglected for decades. I plan to ride for awhile and see what happens.