Of all the jobs I've attempted over the last 4 years, bleeding the brakes has proven to be the most frustrating and time consuming. I followed the advice of many of our experienced members and managed to get the rear brakes working without too much grief. The front brakes are proving to be another matter.
The bike is a '78 Special. I purchased a master cylinder from an XV 250 Virago, rebuilt it with new parts and put it in place, I also rebuilt the callipers - new piston, seals, rubbers and pads. The system has braided brake lines from Banggood.
First attempt at bleeding resulted in no pressure at the handle. There are a plethora of suggestions here on how to deal with that situation and I have tried them all. I have filled the callipers, line and cylinder with fluid and tried to bleed with no result. I have removed the system, filled it with fluid, hung it vertically and tempted tp back bleed with limited success. I have rebuilt the master twice trying to ensure that the piston rubbers are not folded or otherwise distorted in the cylinder. I have replaced all crush washers and banjo bolts with new items and pumped the handle until my biceps rival Stallone. Still, the bloody thing won't work.
I took a thread of stainless wire to the air hole in the bottom of the cylinder and ensured that it was clean. The diameter of the wire was smaller than the hole so I don't believe it caused any enlargement. I took a horse syringe to the beed outlet and managed to draw air and some oil through the system but not enough to provide a constant flow - it just keeps bubbling air out. The banjos are tight and there are no leaks, that I can see, at those junctions or at the calliper
I do notice the, when I put my thumb over the cylinder outlet, it builds pressure and eventually shoots fluid around the garage. I also notice that it builds an element of suction at the outlet as well. The cylinder appears to pump the fluid on the in stroke and suck it back on the release. I am about to tear it down again today but I don't know what else to look for.
Any suggestions??
The bike is a '78 Special. I purchased a master cylinder from an XV 250 Virago, rebuilt it with new parts and put it in place, I also rebuilt the callipers - new piston, seals, rubbers and pads. The system has braided brake lines from Banggood.
First attempt at bleeding resulted in no pressure at the handle. There are a plethora of suggestions here on how to deal with that situation and I have tried them all. I have filled the callipers, line and cylinder with fluid and tried to bleed with no result. I have removed the system, filled it with fluid, hung it vertically and tempted tp back bleed with limited success. I have rebuilt the master twice trying to ensure that the piston rubbers are not folded or otherwise distorted in the cylinder. I have replaced all crush washers and banjo bolts with new items and pumped the handle until my biceps rival Stallone. Still, the bloody thing won't work.
I took a thread of stainless wire to the air hole in the bottom of the cylinder and ensured that it was clean. The diameter of the wire was smaller than the hole so I don't believe it caused any enlargement. I took a horse syringe to the beed outlet and managed to draw air and some oil through the system but not enough to provide a constant flow - it just keeps bubbling air out. The banjos are tight and there are no leaks, that I can see, at those junctions or at the calliper
I do notice the, when I put my thumb over the cylinder outlet, it builds pressure and eventually shoots fluid around the garage. I also notice that it builds an element of suction at the outlet as well. The cylinder appears to pump the fluid on the in stroke and suck it back on the release. I am about to tear it down again today but I don't know what else to look for.
Any suggestions??