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Master Cylinder seal help

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I have a 2005 Orion 125 Pit Bike. I recently bought a new master cylinder and it now it won't work. The bolt where the tube goes from the cylinder to the brake part that's on disc is too big to go into the little O thing on the tube. I do not have pictures sorry.. I am wondering if anyone knows if cork gasket paper will make a good seal? I bought some already to use for the case. I also have some red silicone gasket maker that I am wondering will work? Or does anyone have any suggestions?

Thanks!

FadedVoices

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I ran into the same situation recently. My rear brakes were not working on the 125cc Apollo.  The pads were worn out and so I installed new pads and the caliper still would not pressure up enough to clamp the pads to the disc.  I tried to bleed the air from the system and never could get the master cylinder to pressure up so I surmised that the master cylinder was bad. I ordered the master cylinder from China on Ebay, and when it arrived, it came with a new banjo bolt which was an m10.  The existing brake hose had an M10 banjo bolt at the caliper and an M8 at the cylinder, so I was screwed!  I eventually took both master cylinders apart and replaced the rubber cups in the old cylinder with the new ones from the new cylinder and got it to work some better than it was before.  It will pressure up enough to stop the back wheel but won't lock it up like it should.  One thing that helped mine was to do a "reverse bleed" on the system.  Take a 60ml or 100ml syringe and suck it up full with brake fluid, use a short piece of tubing and attach it to the bleed screw at the caliper; loosen the cap on the master cylinder reservoir (two small screws); open the bleed screw about a quarter turn and start pushing the fluid from the syringe into the bleed screw.  This will force the fluid from the caliper all the way up through the hose and through the master cylinder and the air will come out the top of the reservoir.  When all the air is out and fluid is flowing out the top of the reservoir, while keeping pressure on the syringe, tighten the reservoir cap and close the bleed screw.  This should give you pressure when you apply the brake lever.  You may need to do a traditional bleed in addition but this reverse bleed should get most, it not all, of the air out. I also ordered a brake hose on Ebay that has the M10 banjo fittings on both ends. I think the one that I bought came off of a Yamaha 85cc dirt bike.  The Kawasaki 80 and 85cc dirt bikes have the same hose.  They are 22 inches long and have the M10 banjo fittings on both ends. If you find one on Ebay, be sure to send the seller a question before you bid on it and make sure it has a M10 fitting on both ends and make sure it is long enough to work on your bike. I ordered another master cylinder just like the first one I got ($10.99 and free shipping from China), so when it arrives, I will install the new hose and new master cylinder and hopefully, will get better results.  One word of caution:  The master cylinder that I got from China did not exactly match with the existing mounting holes.  It is aluminum so it is an easy fix if you have a dremmel tool with a small cutter.  I just elongated the mounting holes/slots on the new master cylinder and it worked fine.

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