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Post by yellowbelly on Oct 15, 2013 10:52:04 GMT
I've stripped down the front callipers (one pivot bolt was so seized it had to be cut off), cleaned and rebuilt them with new seals and pads. Now for the easy bit I thought, refilling the system with fluid and bleeding. After topping up the reservoir, I've tried to use a hand vacuum pump, lungs and the lever in every position but I cannot get the fluid past the master cylinder and into the hoses.
I've had the master cylinder out and the element and the cylinder look in good shape.
I'm missing something but I don't know what.
Any ideas would be greatly appreciated.
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HGP
CBT failure
Posts: 23
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Post by HGP on Oct 17, 2013 13:32:45 GMT
I had same issue with my 900s last year. Eventuly sorted by cutting the valve off on old bike inner tube with about 2 inches of rubber each side. Slit the rubber tube to make it flat, and G.clamped the valve section to the top of the master cylinder with a piece of plywood with a hole drilled in it to accommodate the valve. This allowed me to gently pressurize the system with a foot pump and the fluid did flow. Only issue was having to stop and remove tube frequently to top up the reservoir.
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Post by HRHpenfold on Oct 17, 2013 15:07:47 GMT
try using a syringe on the bleed nipple to draw the fluid, failing that use some clear pipe and suck!
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Post by sledgegreen on Oct 18, 2013 0:27:52 GMT
This is how I do this ...
First, when assembling the caliper, push the pistons as far in as possible - this minimises the volume of air to be bled out.
Second, attach a 2-3 foot length of clear plastic tubing (I use windscreen washer tubing from Halfords) to the nipple. Attach the other end to the handlebar if you are bleeding a front brake, or to the top box rack or other suitable support for a rear brake. The length of this tube allows a certain amount of air/fluid to be squeezed out of the caliper. I rarely get a column of fluid more than 6" high, but I like a good safety margin for this task.
Third, with the nipple closed, pump the lever/peddle until you get some pressure, then squeeze and hold the lever/peddle. Whilst holding it, open the nipple. The first few times you do this you will probably only get air out, so nothing to see yet. The relase of pressure will allow the lever to come back to the hand grip, or the pedal to go fully down - hold it there until you have tightened the nipple. Now repeat the sequence of pump - hold - open -hold - close.
You will eventually get some fluid with a lot of air bubbles into the tube. Close the nipple, then wait for the bubbles to rise up the tube so that the fluid settles to the bottom. When you open the nipple, some of the fluid might be sucked back into the caliper - that is OK, but you don't want any air going back in. Once you have a few inches of bubble free fluid at the bottom of the tube, it is time to start pumping again.
One more point - keep a careful watch on the fluid reservoir. It is surprisingly easy to allow it to run dry, and then you start to suck air in at the top, and you ere back to square one.
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Post by crickleymal on Oct 18, 2013 7:52:52 GMT
This is how I do this ... I rarely get a column more than 6" high, Fixed that for you  |
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Post by CD on Nov 14, 2013 21:16:57 GMT
Get a 50ml syringe and a long neoprene tube to push the fluid in from the caliper end. Wrap the bleed nipple with tissue to catch any fluid leaks.
With a long hose, you can work at the brake lever end. Always hold the syringe business end down to keep the air bubble away from the tube. You can use another syringe to suck any excess fluid out of the master cylinder pot.
When done, tie the brake lever back and leave the bike overnight. Any fine bubbles trapped in the system will find their own way out and you will have good firm brakes.
A 100ml syringe needs refilling less often but is VERY hard to push.
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