Hi
I had a fairly big crash about 2 months ago and I'm in the process of rebuilding the bike. After buying a replacement fork and front axle and replacing them I'm having problems with the front brakes. The problem is the lever feels very soft and the brakes don't work. After a few pumps the lever hardens and the brakes work. So I bled them, replaced the brake fluid, but I have the same problem. After the bike moves a couple of feet the brakes get soft again. I have to keep pumping to get the brakes to engage. So they work when the bike is stationary after a few pumps, but as soon as the bike gets moving, the lever gets soft again and there's no pressure. Please help !

 

bleed em again. Its either air still in the lines or the master cylinder is going out.

 

They were working fine before the accident and before replacing the fork, and I'm pretty sure I bled them properly(followed the manual):
1.Removed the cap where most of the blake fluid is
2.Connected tube to the small drain thing on the calipers
3.Pump the fluid until almost empty, tighten the drain with the brake lever pressed
4.Refilled the fluid and repeted step 3 a couple of times
All these for each caliper.
Am I doing something wrong ?
Thanks

 

1. You want to keep the bottom of the resevoir "wet" with brake fluid at all times. If you pump all of the brake fluid out air will go into system.

2. Loosen bleed nut slightly till it flows at a slow rate with tube already installed on it.Make sure tube is airtight. Fluid should come out gradually. Keep tube at a level above the brake caliper, You also want to keep the bleed nut "wet" (fluid sitting at bleed nut because tube is installed) You may see bubbles come up the brake fluid inside the tube.
Tighten bleed nut with tube still on and still wet, do the other caliper the same way.
If you are confident you did it right and still have problems, you may need a new to do further trouble shooting.

 

Just bled them again, followed instructions above, same thing. I think I need to take her to the doctor, I'm out of ideas.

 

If I understand your post correctly it sounds like you pumped the master multiple times with the bleeder open? Can't do that.

Bleeder closed.
Press brake lever.
Open bleeder.
Wait for lever to deperess fully or end of fluid flow.
Close bleeder.

Repeat over and over.

That's it.

 

Yes I pumped the brake with the bleeder open and a tube connected to it. Is that not correct ? Damn, one more try then I checked for leaks too, but could not find any, and as long as the bike remains stationary the brake works great, it's when it gets moving that the lever gets soft.

 

If you're bleeding them properly then you've got a small leak somewhere. Master cylinder not sealing was already mentioned and that makes sense.

 

Yes, it seems you've either got air in the lines/MC or a leak somewhere. A leak should be pretty apparent, so I'm guessing air.

You did bleed the brakes on both calipers right? Make sure both sides are bled to air-free.

 

Yeap, bled both sides using procedures above, brake works fine until the front wheel moves a couple of feet then the lever gets soft again and no brakes. After 2 pumps they work again. I kept pumping to see if there was a leak but couldn't see any fluid coming out anywhere. I'm a diy guy but this looks like one for the pros Thanks for all your advice.