im rebuilding my friends bike for him, and im just about done. the problem im running into is the rear brake wont grab. ive redone this bike from top to bottom, steel braded brake lines, new rotors, and nothing. there is no air in the lines, you can see the brakes move so it not seized up. it just will not grab. any ideas of where to go from here before i buy a new caliper and try that? by the way this is an 06 cbr 600 rr.

 

adjust the rear pedal. I had the same issue with mine recently

 

I wouldnt think the caliper is bad if it was working before you put on the rotor and brake line. You may think the line is bled, but I bet it is not fully bled. You may even want to pull the caliper, hold it higher than the pedal and re-bleed it again. That way, you know the air is moving up. It gets hard to push air downhill when you have such a small piston. Your not moving much oil and the air bubble can just move back and forth and not come out otherwise.

The other thing that may have happened, but unlikely, is you accidentally over extended the brake lever. When you changed your lines, you have no pressure in the system, and if you fully depressed the lever rapidly, it can actually flip or damage the seal inside the piston. If that happens, the brake fluid bleeds back into the resivior around the seal. You will get some pressure, but as soon as the pressure increases, such as when the pads meet the rotor, the extra pressure is not put into the caliper, it is pushed back around the seal. The reason I say its unlikely is most of the time, you can get away with over extending the lever..... but it is possible to ruin the seal.

If I were to bet though, I'd say its not bled. Motorcycles are much more difficult and time consuming than a car to bleed. The best thing to use is a vaccum pump bleeder. If you know of anyone that has one, you may want to borrow it. It makes bleeding brakes on bikes much easier. Without it, it can take a very long time.

 

You can get a cheap one from Pepboys / Autozone. Can't remember the manufacturer but ran me bout $30. Used it when I flushed the brakes.

Actually bleeding the brakes took less time figuring out how to put everything together right and understanding the chitty instructions included (Juliet's How To was far more helpful)

 

for brake fluid:

kind of a weird curve ball but when i first did mine, i got a syringe and injected the brake fluid from the bottom caliper and filled it all the way up to the res. worked great for me.

 

Several brands of mountain bike Hydraulic brake systems use this method. Seems to work well.