Folks, My daughter's wee dirtbike had a front brake issue so I have done the following: Remove front caliper and disassemble, clean, new seals, nipple, 1x new cylinder and pads. Remove brake line and replace with braided hose. Master cylinder removed, cleaned and new piston seal kit installed. Entire front system remounted and charged with new DOT 4 as per OEM standard. Manually bled then bled with a compressor driven vacuum kit. Annndddd....NOTHING! Fluid is getting through but no pressure is building. I have now done this 3 times! I am beginning to lose the will to live! Close inspection of the master cylinder housing reveals that the wee level sighting port has a cracked window. So the question is, would this affect the system building up sufficient pressure to operate correctly? Any advice welcome. Cheers in advance BTD
The cracked window is in the reservoir section so is out with the pressure system. It will have no effect on the operation. The odds are that there is still air trapped somewhere. Have you tried filling it from the bottom using a syringe? I had to replace the master cylinder on a friend's Ducati Scrambler a couple of years ago. I didn't even attempt to fill the reservoir then bleed conventionally. I used a syringe from the caliper and it came perfect right away.
Yeah, tried the reverse fill and top fill, suck fill/pull through! Tried them all, initially felt like a blockage. Removed it again, blew all the lines and openings with the compressor nothing again; its quite puzzling. I've lost count of the number of times I have bled brakes! Im beginning to think the housing itself may be knackered/damaged/worn/out of spec as it is a 2012 bike; and she did prang it recently. I may just bite the bullet and source a new master cylinder. What's frustrating is that its a simple system on a simple bike; how effing difficult can it be!? But I have now spent about 4 hours on a job that should have taken one.
if the flexy hose is a banjo bolt fitting you could use a similar threaded bolt and try blocking the end of the master cylinder to confirm.
