TOPIC:

Hi Guys
looking for some help on bleeding front brakes, i had a broken nipple in one of my calipers so i took the caliper off and replaced it with another one off my spares bike while i get it repaired.
before replacing the caliper i checked that the one on the spares bike was working and then installed it on my good bike i now cant seem to get proper pressure on the brakes, it was never great before which is what led to the bleed nipple being snapped in the first place, i have bled both calipers and have had air and fluid out of both but dont seem to be able to get pressure ,any tips i have read an earlier post and Pete suggested it may take ages of pumping the lever which i will try, at the moment i have the lever tied back to the bars
thanks
Paulb

Hows the master cylinder seals ?, theres two cups in there, one maybe leaking back, kits are on e-bay, or are all the hoses ok?, not swelling under pressure ? or pin hole leaks anywhere ?shouldn't be that hard to bleed the front brakes ... it's all downhill , not sucking air back in thru a nipple ?

KZA13's not wrong. A bad master cylinder seal can cause trouble when bleeding no doubt. When the master cylinder piston is returning, air can be sucked in from the back side of the master cylinder piston.

I've also struggled trying to bleed a front brake system with 2 calipers. It seems you can't push the brake fluid down with the air bubbles fast enough to get the air to the wheel cylinder and out. What I've done in this case is to bleed the system backwards.

You need a 6-8 oz squeeze bottle and a short length of hose that fits nicely over the bleeder screw and the end of the squeeze bottle. Fill the squeeze bottle with brake fluid. Attach the hose to the end of the squeeze bottle.
Remove most of the brake fluid from the master cylinder.
Place the end of the hose over the bleeder screw.
Open the bleeder screw and squeeze the bottle pushing the brake fluid back into the master cylinder. The air bubbles will follow the brake fluid up and you can see them show their ugly bubbles in the brake reservoir. If the fluid in the reservoir gets too high, just suck it out with the squeeze bottle. Obviously, when you go to take the squeeze bottle off of the bleeder screw, you have to close the bleeder screw first.

Oh, and if you think this is a novel idea, it's not. The reason the bleeder screws look like grease nipples is because when they build cars, motorcycles etc. on the assembly line, the brake fluid is added from the brake calipers filling the system and bleeding at the same time.

I will second what Kawboy recommends here and have used this method myself on many occasions.

Depending on your brake line set up, you can also make the job easier by positioning the brake calipers ABOVE the level of the brake master cylinder and bleed them UPWARDS. You first need to find a piece of metal or wood to place between the pads which is the same thickness as your front discs to do this.
This means the air all travels UP through the fluid towards the calipers............

On another note...........I started using SILICON BRAKE FLUID many years ago on all my bikes.
Its 3 times the price of regular CORROSIVE brake fluid, but it does not eat and ruin all your paint on the calipers and master cylinders.
You do need a complete system strip and clean before using it as you CANNOT MIX IT WITH THE REGULAR CORROSIVE PAINT EATING FLUID.

This is what I use

eBay item number:
111889114301


Pete F
UK

Thanks Guys
will take all the comments on board and have another go, i took the bike around the block yesterday and the brakes are working fine but only when the lever is almost back to the bars which is obviously not ideal
thanks again
Paul

Go to a pet store / vet / chemist and get a 50cc plastic syringe. Then put a 6" piece of clear hose on it and use that to push fluid through the bleed nipples. You can push / pull the fluid as many times as you like and you won't waste any fluid.