5th Gen Newbie with Linked Brakes Problem

Hi guys!

A couple of months ago a picked up a 99 VFR800 pretty cheap. It had aftermarket plastics but came with the originals. After swapping those and going through the general tune procedure, it became quite clear something was wrong with the brakes.

When I got it, it had aftermarket front brake and clutch master cylinders. I think they were probably 14 mm pistons. The clutch was super heavy and abrupt, and the front brake was rock hard and had no stopping power. The rear brake was soft and also had no power.

I swapped the clutch master cylinder for a 6th gen and rebuilt the slave cylinder, now that works great!

I replaced the front brake master with a rebuilt OEM unit. Bled the system as per the procedure (several times now). But the brakes still don't work. My latest ride they were better than they had been before, but not confidence inspiring.

The front feels soft for too long of its travel, it does grab and slow you down pretty good, eventually. But the whole system feels inconsistent, If I only use the front brake it usually feels ok (but not great). If I use front and back I can feel the lever get softer as it sends fluid to the rear. Which feels super weird and unpleasant.

Is that just how the linked brakes are?

Thanks for any insight!

1st pic is when I picked it up, 2nd is now.

 

The front brakes are just front brakes, there's nothing hydraulically linked in them to the back. If the front brakes aren't quite right then you should be looking to rebuild the calipers as you may have a build-up of dirt/corrison behind the piston that is causing binding, and that robs a lot of feel.'

At the back your synptoms sound like air in the SMC, and that can be a beast to purge. I got my wife to help when we bled the PCV bleeder, she pressed the pedal down to pressurise the SMC (tilted to let the air out) and then I pressed the SMC while cracking the PCV bleed, then shut the PCV bleed, and she pumped the pedal to force the SMC back out to full extension. Otherwise I think it is possible for air to remain in the PCV bore.