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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Sit on June 23, 2019, 05:22:30 PM
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Help me out guys, at my wits end. Picked up a project sidecar rig last year, 92 75RT with an earls front fork. Got the bike running no issues. Last major thing to do is the front brakes. They held pressure and stopped the bike, but pulsed bad. Figured it was a warped disc, as the previous owner did not even have the rear brake hooked up, that's a lot of work for the front end. So I ordered up new discs and new pads.
Installed the discs last weekend and the pads. Got it all put back together and nada, zip, nothing. No pressure at the brake lever. Hmmm. Ok, bleed the brakes. Bled the brakes, did not see any air come out. Still nothing. Checked around and was told to leave reservoir cap lose and tie off the lever against the handgrip and let the air work itself out on its schedule. Got a bit of pressure doing this, but not nearly enough. I thought maybe since the calipers are mounted at the 4-5 oclock position due to the earl forks, that I had a air bubble in the caliper that wouldn't work its way out. So I put the calipers on top of the discs and let sit. Bingo, strong pressure, like really good. Put them back underneath, nope, nothing. Put them on top, pressure, not as much as letting it sit, but pressure and a few quick pumps gets lots of pressure. So bled the brakes on top of the discs and then mounted them back underneath. Nothing. Couldn't even get much pressure to build pumping them. So bought a compressed air bleeder kit, thinking maybe I can get a strong suction and pull air out. One caliper it seemed to work, a bubble and then nothing but glorious fluid. The left caliper, not so much, the more I tried to suck fluid out, the more air I seemed to get. Don't know where the air is coming from. Both bleeders are new. I made sure not to unscrew it so far that I was pulling air past the threads. No leaks in the lines that I can see. Mind you the brakes "worked" before I tried to fix them. As for the lines, the look like stainless steel lines, one from the master to the splitter that brakes the line into two and then onto the calipers. No leaks around these joints or from any where on the calipers etc.
Any ideas. Someone else on another site mentioned flipping the seal on one of the pistons? But when asked, he did not elaborate or explain how to tell this or fix this. When changing the pads, I used the old pads to push the pistons in. Got a screwdriver in the middle of the pads and just gently rotated it to make a gap and then used my fingers to push the pads back, thereby the pistons. This was not an energetic thing, I went slow and did not force anything. Brake lines did not come off or anything, just old pads to push pistons, swap old pads for new, buttoned them up, mounted and nothing.
Ideas? Particularly from folks who have done K brakes on an earls front end, hell any advice at this point is good advice as I just don't know what to do now.
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Usually changing pads you just pump the lever a bunch of times to get pressure back. With old brake lines the insides have been known to slough off causing a blockage. I've become fond of using a Miti-Vac vacuum bleeder for bleeding brakes but that's another topic.
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The internal lining of the brake hose can delaminate and form a one way valve. It can allow air to be drawn in through a pinhole in the hose but will seal when the brake is applied. After a couple of applications the system will have a significant amount of air in it. This can occur with no sign of a fluid leak.
Regards Martin.
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Help me out guys, at my wits end. Picked up a project sidecar rig last year, 92 75RT with an earls front fork. Got the bike running no issues. Last major thing to do is the front brakes. They held pressure and stopped the bike, but pulsed bad. Figured it was a warped disc, as the previous owner did not even have the rear brake hooked up, that's a lot of work for the front end. So I ordered up new discs and new pads.
Installed the discs last weekend and the pads. Got it all put back together and nada, zip, nothing. No pressure at the brake lever. Hmmm. Ok, bleed the brakes. Bled the brakes, did not see any air come out. Still nothing. Checked around and was told to leave reservoir cap lose and tie off the lever against the handgrip and let the air work itself out on its schedule. Got a bit of pressure doing this, but not nearly enough. I thought maybe since the calipers are mounted at the 4-5 oclock position due to the earl forks, that I had a air bubble in the caliper that wouldn't work its way out. So I put the calipers on top of the discs and let sit. Bingo, strong pressure, like really good. Put them back underneath, nope, nothing. Put them on top, pressure, not as much as letting it sit, but pressure and a few quick pumps gets lots of pressure. So bled the brakes on top of the discs and then mounted them back underneath. Nothing. Couldn't even get much pressure to build pumping them. So bought a compressed air bleeder kit, thinking maybe I can get a strong suction and pull air out. One caliper it seemed to work, a bubble and then nothing but glorious fluid. The left caliper, not so much, the more I tried to suck fluid out, the more air I seemed to get. Don't know where the air is coming from. Both bleeders are new. I made sure not to unscrew it so far that I was pulling air past the threads. No leaks in the lines that I can see. Mind you the brakes "worked" before I tried to fix them. As for the lines, the look like stainless steel lines, one from the master to the splitter that brakes the line into two and then onto the calipers. No leaks around these joints or from any where on the calipers etc.
Any ideas. Someone else on another site mentioned flipping the seal on one of the pistons? But when asked, he did not elaborate or explain how to tell this or fix this. When changing the pads, I used the old pads to push the pistons in. Got a screwdriver in the middle of the pads and just gently rotated it to make a gap and then used my fingers to push the pads back, thereby the pistons. This was not an energetic thing, I went slow and did not force anything. Brake lines did not come off or anything, just old pads to push pistons, swap old pads for new, buttoned them up, mounted and nothing.
Ideas? Particularly from folks who have done K brakes on an earls front end, hell any advice at this point is good advice as I just don't know what to do now.
calipers at 4-5 oclock? huh? where is the bleed nipple? pointing up when bleeding?
picture please.
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I thought maybe since the calipers are mounted at the 4-5 oclock position due to the earl forks, that I had a air bubble in the caliper that wouldn't work its way out.
Ideas?
Do you mean 5 and 7 o'clock positions—left and right?
Look into your master cylinder. Can you see both these ports? Is either of them clogged?
(http://www.motobrick.com/gallery/2/1601-240619012226.jpeg)
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If need be, I will go down the route of replacing brake lines. I don't know how old the are. They look really good though and are not original, they are after market, SS braided lines it looks like to me.
Yes, the calipers mounted in the 4-5 position on the left and yes, 7 oclock or so on the right side, they do matc, so the bleed nipples point pretty horizontal if not a bit down. That is why I tried cutting all of the zip ties for the lines and moving them to the top of the disc for a time and bleeding them there. In this position I have good pressure.
I will double check the reservoir, I know the main hole is clear, the return hole I am not sure.