Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: MarkCR750 on April 25, 2014, 10:36:44 AM
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Because I am bleeding my front brakes!, I am determined to enjoy every hour/day of this miserable ..........sorry I meant enjoyable process :), so far I have connected everything up, I have the started with the conventional method, pumping the fluid down from the reservoir, then switched to pumping fluid back up to the reservoir through the bleed nipples using a syringe, then gone back to conventional method and the fluid coming out of the callipers now has no bubbles, I'm about 1 and a half hours into the process and the brakes are functioning but the lever is spongey.
I have just tied the lever back to the bar and come inside for a coffee, I'm not sure what tying the lever back achieves but read on this forum that it helps?, leave overnight?, can anyone explain?.
Next plan is probably to raise the callipers above the reservoir and conventionally bleed again, PITA though as I have to unbolt the callipers etc, anyway retaining a good positive mental attitude at present, haven't thrown anything across the garage yet or kicked the dog so going well, any advice will be welcome, cheers Mark.
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Mark, kick the dog, it'll make you feel better...
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I don't have a definite answer to tieing the lever back. I'm guessing it leaves a clear line from the caliper to the master cylinder so all the air bubbles can accumulate up top. Let the lever out gently when you untie it and you will probably see some air escape.
Oh! Fun. I'm in a steamy bedroom stripping. ;)
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my method is to fill the calipers full of fluid,,then press the piston in fully to send the fluid up to the mastercylinder,
,repeat the process a few times,and it works for me,also bleed from the nipples to make sure aswell
the spongy lever could be due to the pads not bedded in,and meeting the disc flush,
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I don't have a definite answer to tieing the lever back. I'm guessing it leaves a clear line from the caliper to the master cylinder so all the air bubbles can accumulate up top. Let the lever out gently when you untie it and you will probably see some air escape.
Oh! Fun. I'm in a steamy bedroom stripping. ;)
Thanks for that distinctly unpleasant mental image Lester!.
Cheers all, I've moved onto the XJR giving her an oil change, much more pleasant task!, I will leave the CR brakes until tomorrow hopefully letting nature/physics take their course, but in reality I guess their are a few frustrating hours ahead :), James, plan B will be to go out and purchase a small dog (don't want a big one in case it retaliates).
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check the piston or pistons, and all the caliper pivots etc are all working ok , i had a similar problem on a bike it turned out the caliper was not free to move as it should, and the piston was pushing the pad on to one side of the disk which was tring to bend the disk , the other side was barely touching, so it was never griping the disk tight ,
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use a neighbours dog to kick, saves upsetting the kids!!
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check the piston or pistons, and all the caliper pivots etc are all working ok , i had a similar problem on a bike it turned out the caliper was not free to move as it should, and the piston was pushing the pad on to one side of the disk which was tring to bend the disk , the other side was barely touching, so it was never griping the disk tight ,
Cheers Pete, they are all fine, refurbished, greased etc, I also shimmed the arms to ensure the callipers were square to the discs, I'm sure its air in the system, the lever (Fireblade master cylinder) has got that characteristically soft bouncy feel, I should have stuck at it earlier but I will go for raising the callipers above the reservoir tomorrow after the Stafford show.
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The first part of any master cylnder travel closes off the supply from the reservoir (else the brake fluid will go there instead of down the line to the calipers) so I don't understand what tying the lever in will do. If you want the system left open then leave the lever alone and any air that can travel up the line will properly come out into the fluid reservoir.
With most systems if they are reluctatant to bleed, then if you try bleeding out of the pipe with it disconnected from the caliper to get it free of air, and then reconnect to get the caliper to bleed as well........this is when you can hold the lever in while you reconnect the pipe to the caliper as it will prevent it drawing air back into the pipe end.
These calipers just don't feel like modern stuff in that they never get such a firm pressure at the lever in all the systems I've tried. They have more mechanical flex in them which you can only really judge when you ride and use the brakes to see what you really have.