How firm is your rear brake pedal?

[DMAN999]

^ Yes I'm 99% sure the rear back MC has an O-ring in the cap so if the cap is cracked I'd definitely replace it.
That being said, I change my brake and clutch fluid every 4-5 years and on my 2000 Vamx the rear brake is always tight.
I have EBC HH pads and light pressure is all I need to brake, it I apply too much pressure I can easily lock the rear wheel.

 

[EAGLEPI]

I try not to use the rear brake, but it doesn't work well with a 600 lb bike. So I lowered my pedal purposely so that when I do use it, it takes a conscious effort. I am not used to using the back brake at all.

With that being said, I would say there is probably something wrong with the caliper affecting the braking effort/pedal travel. I'd inspect everything; pads, lines, caliper pistons; clean it all with brake cleaner; reassemble; and then bleed the system well.

I've always had the bad habit of using my front brake much more than my rear. I know it isn't good but for some reason i was unable to not go for the front brake first. I am going to do my best to "brake" that habit..............:rofl_200:

 

[DMAN999]

^ The front brake is supposed to be 60-80% of your braking.
http://www.webbikeworld.com/Motorcycle-Safety/braking-tips.htm

 

[TB99Max]

I'm another one with the same issue! Mine is a 99. I started with the caliper, I got a rebuild/seal kit. That didn't help. Then I bought a master cylinder rebuild kit and that didn't help. But I didn't pay close attention when I pulled it apart and I have a feeling I might have reassembled it wrong. Don't know what it's called but the corkscrew looking piece inside the MC has 2 tapered o-rings on it and I couldn't find a detailed enough diagram that showed which way they went. So I also have a question for the Vmax guru's...... Do you feel that a brake vac is necessary to bleed them properly? Or when you do bleed them by hand if you had all the fluid out, how many times roughly do you pump them and open the bleeder?

 

[Zeus36]

I kept seeing oil spray on the lower engine nose cone on my other motorcycle while riding in Albuquerque a few years ago. Looked everywhere but didn't find the source until I pulled off the chrome dress cover above the rear master cylinder and found the master cylinder cap, screws and gasket were GONE. Just the rubber diaphragm was sitting on top of the fluid. No idea how long they had been lost to the road gods.
Picked up replacement parts and flushed the system.

No more chrome dress cover hiding those parts now!

 

[blaxmax]

I'm another one with the same issue! Mine is a 99. I started with the caliper, I got a rebuild/seal kit. That didn't help. Then I bought a master cylinder rebuild kit and that didn't help. But I didn't pay close attention when I pulled it apart and I have a feeling I might have reassembled it wrong. Don't know what it's called but the corkscrew looking piece inside the MC has 2 tapered o-rings on it and I couldn't find a detailed enough diagram that showed which way they went. So I also have a question for the Vmax guru's...... Do you feel that a brake vac is necessary to bleed them properly? Or when you do bleed them by hand if you had all the fluid out, how many times roughly do you pump them and open the bleeder?

A brake vac or mityvac is like having 4 hands and takes no time in comparison to doing by hand- also there is reverse bleeding with a syringe.
My vac has paid itself off years ago as I bought it in 1976.

 

[TB99Max]

HOLY CRAP..... 1976! I wasn't even born yet !

 

[D-Max2012]

Holy ****!!!..
Today, I was replacing my fuel sender unit.. (Hate that I have to damn near take the bike apart to get to the freakin thing).. With the back tire and shielding removed, I could see from the opposite side of the bike. Getting ready to re-assemble everything I noticed the Rear Brake Master Cylinder Reservoir (RBMCR), looked like someone poured acid over the cap. It was totally broken up and crumbling away. I could actually see the lip of the rubber diaphragm that should have been covered by the cap. Note: I was just in that area last week, doing some testing on the fuel sender, and from the outside of the bike, the reservoir cap looked fine.
I'm not 100 sure, if loosing pressure in the "RBMCR" would cause my brakes to go spongy, or fail completely, but I just ordered a full replacement set. I figure, if it's got a diaphragm in there, it must be there to build pressure. I forgot to take a picture, but I will post what it looked like, when the replacement get here. No riding for me till it does.

Just changed out the RBMC Cap, diaphragm and seat.

Look what I found the previous owner did..



Looks like someone spilled acid, and did not flush with water after spillage.
Note: the negative terminal of the battery, sits right above the Rear Brake MC.

looks like they were trying to top off the battery without pulling it out of the bike. Not good.. Now I have to dig down deep, to see if anything else was affected.

Boy if I had the money, I would have purchased brand new!!!

Now, my rear break only goes down about 3/4 inch, before the break feels like it's getting tight on the rotor.

 

[racerboy]

How old is the fluid, is it orignal from factory?

Perhaps a fluid transfusion is in your future?
It may need new fluid and a good bleed. Moisture absorption.:confused2:

Original?? Mang! Its probably beyond black.

 

[davesax36]

I bled mine for more than 30 minutes today. A few times I got some black junk coming out, but the fluid in the reservoir was fairly clean, and it was coming out clear by the time I gave up. I can push the lever probably 3" with my foot. I was pumping probably 15 times before each bleed release and still not getting any firmness in the pedal even with my hand. Super frustrating. I think I've got another complete rear brake line and caliper here somewhere, so I might try that.

 

[[email protected]]

I bled mine for more than 30 minutes today. A few times I got some black junk coming out, but the fluid in the reservoir was fairly clean, and it was coming out clear by the time I gave up. I can push the lever probably 3" with my foot. I was pumping probably 15 times before each bleed release and still not getting any firmness in the pedal even with my hand. Super frustrating. I think I've got another complete rear brake line and caliper here somewhere, so I might try that.

Is your setup stock?

Sent from my SM-G930V using Tapatalk

 

[Fire-medic]

Something's wrong there. Sounds like a separation in the hose. See any blister on the side of the line? If it happened to your body, it would be an aneurysm. Replace the line, try again. Mityvac is your friend, though on clutch lines I prefer the syringe/reverse-bleed method.

I bled mine for more than 30 minutes today. A few times I got some black junk coming out, but the fluid in the reservoir was fairly clean, and it was coming out clear by the time I gave up. I can push the lever probably 3" with my foot. I was pumping probably 15 times before each bleed release and still not getting any firmness in the pedal even with my hand. Super frustrating. I think I've got another complete rear brake line and caliper here somewhere, so I might try that.

 

[davesax36]

Is your setup stock?

Sent from my SM-G930V using Tapatalk

Yup.

 

[davesax36]

Something's wrong there. Sounds like a separation in the hose. See any blister on the side of the line? If it happened to your body, it would be an aneurysm. Replace the line, try again. Mityvac is your friend, though on clutch lines I prefer the syringe/reverse-bleed method.

Half mityvac, half hand pumping. I'll work on it a bit tomorrow again. I'm sure it'll just fix itself in like 2 minutes.