Need Help Brakes Vfr1200

Hi Guys tonight ive had a really bad experience on my VFR1200, going through a really busy tunnel just about made it through the rear brake is going hard on , \im not even touching the brake pedal. This is after riding for 2 miles before tunnel. Im not sure where the brake pressure is coming from. Has anyone had problems with the ABS causing this to put pressure on the brakes. Calipers have been cleaned by motorbike mechanic. Have swapped the Rear Master cylinder for another but got a rebuild kit on way. Any help much Appreciated.

 

OMG ! thats as scary as a date with margret thatcher, hey, lad. ? for safety, dont ride again until its fixed.

 

Yikes; that's more like what happens to the linked brakes on the ST1300. Glad you and your bike are OK.

On the 1200 I think the likeliest failure point is at the master cylinder if you have some crud that is blocking the tiny return port. If that clogs, your brake pressure can't release, and as the brake and fluid heat up the brake will likely come on harder.

You can do diagnostics to find where the blockage is. If the brake releases when you crack the bleed nipple then the calliper is OK. If the brake releases when you crack the hose at the master, then you can be confident the issue is at the master.

 

Thanks for replying, Ive just woken up and had the same thinking if there is slight binding even though ive not touched the rear brake fluid expands a small amount and has to go through the very small return hole in master cylinder and It cant if its blocked on the second hand master cylinder I brought. Ive taken the old one apart and the return hole is so small you cant even clear it with a pin, so the expanding fluid will put brakes on more and more I guess. I wished I could buy a new one but I guess rebuild ole one for now..

 

Well looks like the rebuild kit has fixed the issue, was a blocked retrn hole clear now.

 

This can happen if you dont change your brake fluid when you should. It can also happen in the front reservoir. Whie/yellow waxy Solids form and wreak havoc in the brakes.

 

Thats what I found in the secondhand Master I brought a load of white stuff blocking the small hole up.. The original problem with the brakes was them sticking but this was a sticking Cylinder due to a rusty ball joint , the rust was sticking to the cylinder wall ( not enough grease in there to keep water out I guess. All good now used bike for work today all great..