I have a 200 CC 4 stroke trail bike. The front brake was stiff and eventually I bled all the brake fluid. When filling the master reservoir on the handle bars none of the fluid is leaving the reservoir and/or filling the brake line. I have loosened/tightened the bleeder valve on the calipers and pumped the hand brake to no avail. Should the break line fill completely by gravity? What am I missing? As always, thank you in advance because the help always comes!
It's a lesson in patience to change brake fluid. Last time I did it, it took about 45 minutes of pumping the lever and tapping on the line to get it all bled out.
It seemed like it went from no pressure at all, to stiff as it was going to get in a matter of a few minutes too.
Back bleed it. Get a big syringe and tube to fit the bleeder, fill up the syringe and attach it to the caliper bleeder then crack it open. SLOWLY force new fluid in to the caliper and then up the line to the MC. Just zip tie the lever to the grip so it is open and it should just bubble up in to the MC forcing most if not all the air out of the sytem. Tapping with a wrench or something helps break stubborn bubbles loose and send the on up the line.
Most of the air must be out because the brake is slowing me down and there is resistance on the brake lever. I spent about 1 hour pumping the lever, purging, closing the purge and repeating. I guess I will continue until it give me the right results!
As Pat nsaid it is best to fill from the bottom (brake) up to the reservoir. Here is a link to another thread and at the end is a picture of what I use to do it