Hey guys, I've finished up the engine rebuild on my 04 KTM 125sx. The last thing I needed to do was rebuild the master and slave cylinder for the front brake. I put in new seals, cleaned them each out, and put in new springs, copper washers, and plunger. I cracked the bleeder on my caliper and pushed dot 4 fluid up and to my master where it is now full. I made sure that the bleed syringe didn't have any air in it what so ever. I was surprised that I had no pressure at all on the lever. I can pump it 20 times and never build pressure. I tried zip-tying it to the bar and leaving overnight with no success. Am I missing something here? Before rebuilding, the system would build pressure but was spongy and the lever wasn't a strong lever like it should have been. Any help or tips appreciated, thanks
There is obviously still air trapped in the system somewhere. You can try hanging the caliper above the master overnight, tapping the master to work the air loose also works at times.
I use a vaccum pump so I never have these issues anymore. Might be worth the investment for you as well.
There is obviously still air trapped in the system somewhere. You can try hanging the caliper above the master overnight, tapping the master to work the air loose also works at times.
I use a vaccum pump so I never have these issues anymore. Might be worth the investment for you as well.
Air is probably trapped behind the caliper pistons. With the bleed screw closed push the caliper against the rotor. Then pump lever again. Repeat until lever is hard. Another method is to push the caliper in with the bleed screw slightly cracked. Close the bleed, screw, and pump up the lever.
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I tried this tonight to no avail, might give willbilly's idea a try tomorrow
On a bike that old the caliper pins my be corroded. Clean both up and apply grease. Also check that the pins are not bent.
not new but have lots of life left on them. I will try lever pressure in the morning.
I just got back in from doing that. They were definitely sticking and gummed up. Fresh grease and boots and will keep working on it in the morning.
Last time i did it that way after i'm going crazy pumping 200 times, put the Caliper up and the Master Cylinder down , was done in 5 Minutes that way.
But Piston,Master Cylinder ,Brake Pads and Brake line was completely New
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