03-26-2020, 07:10 AM
That's very well done 17EX, i find these repairs with an explanation at the end very helpful and the internet has been so helpful in finding answers and inspiration.
Very precise explanation and it shows the quality of the mechanic in question, i had a similar issue with my 2006 honda cb900 which has the same brake parts, the front brakes dragged initially and freed up with some use but the situation got worse over time, changed the brake fluid, no change, took out and cleaned the seals and pistons; no change.
The only parts left were the master cylinder, it felt "sticky" , it turned out that the rear seal had swollen and was too big in the bore causing the drag, i gradually dressed it up with wet and dry sandpaper and that freed it up enough to make it work as it should but replaced the whole assembly in the end, i also had the problem with my 1977 honda cb550 which developed a blocking of the small hole and came right after careful cleaning it, i could not get the pressure to build up before that because the air could not escape through it.
I did not even know that the small hole existed and only found out after a clear picture of it on the net.
This tiny hole is the only vent the fluid has to reset and relieve any air and surplus fluid from the brake calipers, it lives under the stainless deflector on the bottom of the reservoir and as soon as the first seal is pushed forward to engage the brakes is behind the seal which is why it has to be so small.
The bigger hole is only there to return any fluid that may pass the main seal on the front of the piston when pressure is applied and has no connection to the pressurized part of the system.
The second seal on the piston is there only to stop any fluid that is not under pressure from leaking out of the cylinder, it is never under pressure and just wipes the fluid back into the reservoir.
Here is a link to a video showing the repair of the main piston with a small trick i used to hold the spring pressure in to make it easy to repair;
https://www.youtube.com/watch?v=QM5Wh6GsLO0
Thanks for posting your solution.
Very precise explanation and it shows the quality of the mechanic in question, i had a similar issue with my 2006 honda cb900 which has the same brake parts, the front brakes dragged initially and freed up with some use but the situation got worse over time, changed the brake fluid, no change, took out and cleaned the seals and pistons; no change.
The only parts left were the master cylinder, it felt "sticky" , it turned out that the rear seal had swollen and was too big in the bore causing the drag, i gradually dressed it up with wet and dry sandpaper and that freed it up enough to make it work as it should but replaced the whole assembly in the end, i also had the problem with my 1977 honda cb550 which developed a blocking of the small hole and came right after careful cleaning it, i could not get the pressure to build up before that because the air could not escape through it.
I did not even know that the small hole existed and only found out after a clear picture of it on the net.
This tiny hole is the only vent the fluid has to reset and relieve any air and surplus fluid from the brake calipers, it lives under the stainless deflector on the bottom of the reservoir and as soon as the first seal is pushed forward to engage the brakes is behind the seal which is why it has to be so small.
The bigger hole is only there to return any fluid that may pass the main seal on the front of the piston when pressure is applied and has no connection to the pressurized part of the system.
The second seal on the piston is there only to stop any fluid that is not under pressure from leaking out of the cylinder, it is never under pressure and just wipes the fluid back into the reservoir.
Here is a link to a video showing the repair of the main piston with a small trick i used to hold the spring pressure in to make it easy to repair;
https://www.youtube.com/watch?v=QM5Wh6GsLO0
Thanks for posting your solution.